Review ArticleGastric Carcinogenesis and Underlying Molecular MechanismsHelicobacter pylori and Novel Targeted Therapy

Toshihiro Nishizawa12 and Hidekazu Suzuki1

1 Division of Gastroenterology and Hepatology Department of Internal Medicine Keio University School of Medicine35 Shinanomachi Shinjuku-ku Tokyo 160-8582 Japan

2Division of Research and Development for Minimally Invasive Treatment Cancer Center Keio University School of Medicine35 Shinanomachi Shinjuku-ku Tokyo 160-8582 Japan

Correspondence should be addressed to Hidekazu Suzuki hsuzuki1201gmailcom

Received 14 August 2014 Accepted 15 October 2014

Academic Editor Shigeru Kamiya

Copyright copy 2015 T Nishizawa and H Suzuki This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The oxygen-derived free radicals that are released from activated neutrophils are one of the cytotoxic factors of Helicobacterpylori-induced gastric mucosal injury Increased cytidine deaminase activity in H pylori-infected gastric tissues promotes theaccumulation of variousmutations andmight promote gastric carcinogenesis Cytotoxin-associated geneA (CagA) is delivered intogastric epithelial cells via bacterial type IV secretion system and it causes inflammation and activation of oncogenic pathways Hpylori infection induces epigenetic transformations such as aberrant promoter methylation in tumor-suppressor genes Aberrantexpression of microRNAs is also reportedly linked to gastric tumorogenesis Moreover recent advances in molecular targetingtherapies provided a new interestingweapon to treat advanced gastric cancer through anti-human epidermal growth factor receptor2 (HER-2) therapies This updated review article highlights possible mechanisms of gastric carcinogenesis including H pylori-associated factors

1 Introduction

Helicobacter pylori infection is one of the most prevalentinfectious diseases worldwide and 40ndash50 of the globalhuman population is estimated to be infected H pylorihas been identified as a group 1 carcinogen by the WorldHealth Organization International Agency for Research onCancer (WHOIARC 69372 Lyon CEDEX 08 France) and isassociated with the development of noncardia gastric cancerEradication of H pylori infection has been reported as aneffective strategy for both the treatment of peptic ulcersand gastric mucosa-associated lymphoid tissue (MALT) lym-phoma as well as prevention of gastric cancer [1ndash3]

A randomized controlled trial (RCT) in Japan demon-strated significant prophylactic effects ofH pylori eradicationon the development of metachronous gastric carcinoma afterendoscopic resection [1] According to a systemic review of 15papers H pylori eradication significantly reduces the preva-lence of gastric cancer by approximately one-third [4]A recent meta-analysis of RCTs also shows that H pylori

eradication seems to reduce gastric cancer risk [relative risk(RR) 065 95 confidence interval (CI) 043ndash098] [5] In2009 the committee of the Japanese Society for HelicobacterResearch (JSHR) revised the guidelines for diagnosis andtreatment ofH pylori infection [6]H pylori eradication ther-apy achieved a strong recommendation because it is usefulfor the treatment of gastric or duodenal ulcers treatmentand prevention ofH pylori-associated diseases such as gastriccancer and inhibition of the spread of H pylori infection

Bacterial virulence factors such as cytotoxin-associatedgene A (CagA) cause inflammation and activate oncogenicpathways Activated neutrophils are the main source of reac-tive oxygen species (ROS) and reactive nitrogen species pro-duction in H pylori-infected stomachs Excessive oxidativestress can damage DNA in gastric epithelial cells indicatingits possible involvement in gastric carcinogenesis [7] Gastriccancer arises frommultiple genetic and epigenetic alterationsin oncogenes tumor-suppressor genes cell cycle regulatorscell-adhesion molecules and DNA repair genes

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015 Article ID 794378 7 pageshttpdxdoiorg1011552015794378

2 BioMed Research International

Recent studies provided evidence that expression ofan aberrant DNARNA editing enzyme activation-inducedcytidine deaminase (AID) might be a mechanism of muta-tion accumulation in the gastric mucosa during H pylori-associated gastric carcinogenesisThe roles ofmicroRNAs areincreasingly apparent and aberrant expression of microR-NAs may contribute to the development and progression ofgastric cancer Moreover recent advances in molecular ther-apies provided a new interesting weapon to treat advancedgastric cancer through anti-human epidermal growth factorreceptor 2 (HER-2) therapies

Consequently this paper summarizes the molecularmechanism of H pylori-associated gastric carcinogenesis

2 Oxidative Stress

Oxygen-derived free radicals that are released from acti-vated neutrophils are considered potential toxic factorsthat contribute to H pylori-induced gastric mucosal injuryNeutrophils express myeloperoxidase which produces thehypochlorous anion (OClminus) OClminus reacts with the ammo-nia (NH

3

) which is produced from urea by H pylori-associated urease to yield a lipophilic highly cytotoxicoxidant monochloramine (NH

2

Cl) that freely penetratesbiological membranes to oxidize intracellular components[8] Free radicals including ROS and reactive nitrogenspecies can bind with nucleic acids turning them intomutated forms that play a role inmultistep carcinogenesis [9]

The CD44 variant (CD44v) which is a cell-surfacemarker that is associated with cancer stem-like cells inter-acts with a glutamate-cystine transporter and controls theintracellular level of reduced glutathione (GSH) [10] Humangastrointestinal cancer cells with a high level of CD44 expres-sion revealed an enhanced capacity for glutathione synthesisand defense against ROS These findings indicate that cancerstem-like cells with CD44v expression could have an ROSdefense system that results from glutathione synthesis

H pylori upregulates spermine oxidase (SMOX) in gastricepithelial cells SMOX metabolizes the polyamine spermineinto spermidine and generates H

2

O2

which causes apoptosisand DNA damage However a subpopulation of SMOXhigh

cells is resistant to apoptosis despite their high levels ofDNA damage Chaturvedi et al reported that activation ofepidermal growth factor receptor (EGFR) and erythroblasticleukemia-associated viral oncogene B (ErbB2) by H pyloriresults in survival of gastric epithelial cells with DNA damage[11]

3 CagA

Epidemiological evidence indicates that H pylori strainscontaining CagA are more virulent CagA-positive H pyloriincreases the risk of both intestinal and diffuse types ofnoncardia gastric cancer [12] The CagA protein of H pyloriwhich is delivered into gastric epithelial cells via bacterialtype IV secretion system is an oncoprotein that can inducemalignant neoplasms After the CagA protein is injectedinto the host cell cytoplasm the EPIYA (Glu-Pro-Ile-Tyr-Ala)

motif of CagA is tyrosine-phosphorylated by host Src kinasesand subsequently changes the gastric epithelial morphology[13] CagA binding to the protooncogene Src homology2-containing protein tyrosine phosphatase (SHP-2) causesaberrant activation of SHP-2 and consequently of the ERK-MAPK (mitogen-activated protein kinase) pathway whichhas been reported to play a role in carcinogenesis by inducingmitogenic responses [14] East Asian CagA that contains theEPIYA-D motif demonstrates higher affinity for SHP-2 thanWestern CagA These findings are consistent with the factthat East Asian strains dominate in countries with the highestrates of gastric cancer [15]

On the other hand CagA interacts with many signalingmolecules (eg Per-1 c-Abl Crk proteins Grb proteins andc-Met) that are important for the regulation of cell prolif-eration scattering and morphology (Figure 1) CagA thatis translocated into the host cell is degraded by autophagyand short-lived However CagA that is translocated intoCD44v9-positive gastric cancer stem-like cells which arecharacterized by ROS resistance that results from theirrich GSH content is thought to escape ROS-dependentautophagy resulting in gastric carcinogenesis [16]

4 AID

The DNARNA editing enzyme AID is a 198 amino acidprotein that directly converts cytosine into uracil (Figure 2)AID is specifically induced in germinal center B cells tocarry out somatic hypermutation and class-switch recom-bination which are two processes that are responsible forantibody diversification Because of its mutagenic potentialAID expression and activity are tightly regulated tominimizeunwanted DNA damage Surprisingly AID is also induced byinflammation and microbial infections in nonimmune cells

H pylori infection mediates aberrant AID expression ingastric mucosal epithelial cells Additionally AID expressionwas shown to be triggered by proinflammatory cytokinessuch as TNF-120572 or IL-1 and correlated with mononuclearcell infiltration and intestinal metaplasia After eradicationof H pylori the level of AID expression decreases [17]Strong evidence indicates that CagA-positive H pylori-mediated upregulation of AID resulted in the accumulationof nucleotide alterations in the TP53 tumor suppressor genein gastric cells [18] Whole-exome sequencing revealed thatsomatic mutations accumulated in various genes in inflamedgastric tissues The mutations that accumulated in gastrictumors as well as gastric mucosal tissues with H pylori-induced gastritis were predominantlyC GgtT A transitionsin GpCpXmotifs which aremarkers of cytidine deaminationthat are induced by AID [19] Increased cytidine deami-nase activity in H pylori-infected gastric tissues appears topromote the accumulation of various mutations and mightpromote gastric carcinogenesis

5 Oncogenes

Mutational activation andor amplification of several onco-genes such as ErbB KRAS PIK3CAMET andMYChas beendocumented in gastric cancer

BioMed Research International 3

Type IV secretion system

N terminalC terminal

EPIYA-motifsCagA

SHP-2

Cell motility and invasion

Cell proliferation

ERK-MAPKGrb

Par-1

C-met

Polarization defects

Figure 1 CagA and major functions CagA is delivered into gastricepithelial cells via bacterial type IV secretion system CagA interactswith many signaling molecules that are important for the regulationof cell proliferation polarity and motility

NH2

N

N

O

OO N

HN

H2O NH3

C

G G

U

T

AAID deamination DNA replication

Cytosine Uracil

Figure 2 Activation-induced cytidine deaminase (AID) as theDNARNA editing enzyme AID is induced by H pylori infectionand promotes the accumulation of various mutations

Epidermal growth factor receptor (EGFR) a memberof ErbB receptor family is involved in the regulation ofgastric mucosal cell proliferation and progression of gas-tric cancer Overexpression of ErbB1 (EGFR) and ErbB2(HER-2) is found in 27ndash64 and 6ndash34 of gastric cancerrespectively [20] Activation triggers a cascade of eventsthat involves autophosphorylation and activation of tyrosinekinase domain RasRafMAPK pathway phospholipase C-120574and phosphatidylinositol-3-kinase (PI3K)Aktmammaliantarget of rapamycin (mTOR) Ras an oncogenic smallGTPase has three isoforms namely K-Ras H-ras and N-ras Constitutive activation of Ras and Ras-related proteinspromotes cell proliferation and increase invasion and metas-tasis while inhibiting apoptotic cell death K-RAS gene wasfound to be mutated (codon-12) in intestinal-type cancer butnot in diffuse-type cancer [21] K-RAS gene mutations in Hpylori-associated chronic gastritis aremore frequent in gastriccancer patients than in cancer-free patients suggesting thatK-RAS mutation may be involved in the early stage of gastriccarcinogenesis [22]

Trastuzumab is a monoclonal antibody that binds toextracellular domain of the receptor acting by blockage ofthe HER-2 receptor cleavage inhibition of dimerization andthe induction of antibody-dependent cellular cytotoxicity(ADCC) In phase III ToGA trial the addition of trastuzumabto standard cisplatin and 5-fluorouracil improved overall

survival from 111 to 138 months in patients with HER-2 amplified gastric adenocarcinomas [23] In phase IIIEXPAND trial the addition of cetuximab (chimeric mono-clonal anti-EGFR antibody) to standard cisplatin and cape-citabine did not improve progression free survival in patientswith advanced gastric cancer [24] Similarly in phase IIIREAL-3 trial the addition of panitumumab (fully humanizedmonoclonal anti-EGFR antibody) to epirubicin oxaliplatinand capecitabine did not improve overall survival in patientswith advanced gastric adenocarcinoma [25] In additionretrospective biomarker analysis has failed to identify a clearpatient subset that would derive benefit from EGFR-directedtherapies Lapatinib is dual tyrosine kinase inhibitor active onEGFR and HER-2 In phase III TYTAN trial the addition oflapatinib to weekly paclitaxel in second-line setting improvedoverall response rate in patients with HER-2-positive gastricadenocarcinomas (odds ratio 385 95 CI 180ndash887 119875 lt0001) but did not significantly improve overall survival(lapatinib+paclitaxel 110 versus paclitaxel 89 months 119875 =0104) [26]

Phase III GRANITE-1 study evaluated the efficacy ofmTOR inhibitor everolimus compared to the best supportivecare in patients with advanced gastric cancer that progressedafter initial chemotherapy In this study median survivalwas reportedly 539 months with everolimus versus 434months with placebo (HR = 090 95 CI 075ndash108) [27]Patients in this study were not preselected with respect toPI3KAKTmTOR pathway alteration

6 Tumor-Suppressor Genes

The p53 tumor-suppressor gene the guardian of humangenome is frequently inactivated in the tissue of gastric can-cer aswell as in preneoplastic lesions by loss of heterozygosity(LOH) missense mutation or frame-shift deletions [12] Thep53 53 kDa phosphoprotein is a transcription factor forincluding DNA repair genes in response to DNA damageActivation of p53 also arrests the cell cycle to allow enoughtime for fixation of DNA damage However if DNA damageis beyond repair p53 induces apoptotic cell death Themutations of p53 have also been identified in gastric adenomaand intestinal metaplasia We have recently reported that p53downregulation due to increased MDM2-phosphorylationinduces autophagy which causes CagA oncoprotein degra-dation translocated from the bacterial body of H pylori togastric epithelial cells and then inhibits mTOR [16]

APC is a multidomain protein with binding sites fornumerous proteins including Wnt signaling pathway APCplays major role in cell adhesion cell migration spindle for-mation and chromosome segregation [28] APC mutationsare the second most frequent mutations in gastric cancerand have been observed in 30ndash40 of intestinal type cancerand in less than 2 of diffuse type cancer [29] The muta-tions of APC have also been identified in gastric adenomaand intestinal metaplasia indicating that they occur duringpreneoplastic stage of gastric cancer development LOH andmutations of phosphatase and tensin homolog (PTEN) wereobserved in gastric cancers as well as in precancerous lesions[30]

4 BioMed Research International

7 DNA Methylation

Methylation of CpG islands in a promoter region inhibitsgene transcription by interfering with transcriptional initia-tion and serves as an alternative mechanism of inactivatingtumor suppressor genes without gene mutation Amongfactors known to cause aberrant DNA methylation agingand chronic inflammation are known to promote the accu-mulation of DNA methylation H pylori infection inducesaberrant promoter methylation in tumor-suppressor genesincluding p16 LOX and CDH1 Furthermore a numberof tumor suppressor genes including hMLM1 p14 p15GSTP1 RASSF1 COX-2APC CDH4DAP-K THBS1 TIMP-3 RAR120573 MGMT CHFR DCC RUNX3 and TSLC1 areknown to be silenced by hypermethylation in gastric cancer[31] (Figure 3)

Recent meta-analysis revealed that the frequencies of p16promoter methylation in gastric cancer tissue were higherthan those of normal and adjacent tissues [Normal odds ratio(OR) = 2304 95 CI = 1355ndash3915 119875 lt 0001 AdjacentOR = 442 95 CI = 166ndash1176 119875 = 0003] Furthermoresignificant associations of p16 promoter methylation withTNM stage histologic grade invasive grade and lymph nodemetastasis are shown (TNM stage OR = 360 95 CI 217ndash598 119875 lt 0001 Histologic grade OR = 263 95 CI 155ndash445 119875 lt 0001 Invasive grade OR = 344 95 CI 168ndash706119875 = 0001 Lymph node metastasis OR = 268 95 CI 166ndash432 119875 lt 0001) [32]

Forkhead box (Fox) proteins comprise an evolutionarilyconserved family of transcriptional regulators In partic-ular FOXD3 bound directly to the promoters and acti-vated transcription of genes that encode the cell deathregulators CYFIP2 and RARB Recent methylation pro-file analyses revealed that FOXD3-mediated transcrip-tional control of tumor suppressors is deregulated by Hpylori infection-induced hypermethylation [33] Alterna-tively CagA enhanced DNA methyltransferase 3B andenhancer of zeste homologue 2 expression which resultedin the attenuation of let-7 expression by histone and DNAmethylation [34] Aberrant epigenetic silencing of let-7expression leads to Ras upregulation

DNA methylation levels of specific CpG islands are asso-ciated with risk of gastric cancer Nanjo et al identified sevennovel gastric cancer risk markers that reflect epigenomicdamage that is induced by H pylori infection and thehypermethylated CpG islands had high ORs (127ndash360) in ananalysis [35]Moreover 5-aza-21015840-deoxycytidine (5-aza-dC) isa DNA demethylating agent Niwa et al showed that 5-aza-dC treatment can prevent H pylori-induced gastric cancersin the Mongolian gerbil model [36] Removal of inducedDNA methylation andor suppression of DNA methylationinduction could become a target for prevention of chronicinflammation-associated cancers

8 Angiogenesis

Elevated concentrations of vascular endothelial growth factor(VEGF) have been described in patients with advancedgastric cancer and correlated with decreased survival VEGF

Methylation induction

Tumor suppressor gene

Promoter region

Figure 3 DNA methylation inactivates tumor suppressor geneswithout genemutation Chronic inflammation byH pylori infectioninduces aberrant promoter methylation in tumor-suppressor genes

and VEGF receptors are overexpressed in 36ndash40 of gastriccancer Phase III AVAGAST and AVATAR studies haveevaluated the addition of bevacizumab (anti-VEGF-A mon-oclonal antibody) to first-line platinum-fluoropyrimidinechemotherapy in advanced gastric cancer patients but failedto demonstrate improved survival [37 38]

Phase III REGARD trial evaluated the efficacy oframucirumab a monoclonal antibody VEGFR-2 antagonistcompared to the best supportive care (BSC) in patientswith advanced gastric cancer that progressed after previouschemotherapy Median survival was 52 months with ramu-cirumab versus 38 months with placebo (HR = 0776 95CI 0603ndash0998 119875 = 0047) [39] Based on data from thisREGARD trial the Food and Drug Administration (FDA) inUnited States approved ramucirumab as second-line therapyfor patients with advanced gastric cancer

Apatinib inhibitor of VEGF-2 showed improved pro-gression free survival and overall survival in heavily pre-treated patients withmetastatic gastric cancer in phase II trial[40] Phase III trial of apatinib is ongoing

9 MicroRNAs

MicroRNAs are noncoding RNAs that are comprised of 18ndash24 nucleotides that can posttranscriptionally downregulatevarious target genes Recent studies have shown that aconsiderable number of microRNAs are altered followinginfection with H pylori and specific microRNA deregula-tion was found to contribute to host inflammation cell-cycle progression inhibition of apoptosis cell invasion andmetastasis [41] MicroRNAs that function as oncogenesincluding miR-17 miR-21 and miR-106a were upregulatedwhereas microRNAs that function as tumor suppressorssuch asmiR-101miR-181miR-449miR-486 and let-7a weredownregulated in gastric cancer [42 43]

BioMed Research International 5

Shiotani et al reported that the expression of oncogenicmicroRNAs (miR-1792 and themiR-106b-93-25 clustermiR-21 miR-194 and miR-196) is significantly higher in theintestinal than nonintestinalmetaplasiaH pylori eradicationimproves microRNA deregulation but not in the intesti-nal metaplasia MicroRNA deregulation is not completelyreversible by eradication alone in long-term H pylori colo-nization [44]

Runt domain transcription factor 3 (RUNX3) is a tumorsuppressor that is silenced in cancer via hypermethylationof its promoter Previously we reported that H pylorieradication significantly increases RUNX3 expression ingastric epithelial cells [45] Lai et al reported that miR-130b expression is upregulated in gastric cancer and thisis inversely associated with Runx3 hypermethylation [46]miR-130b overexpression increases cell viability and reducescell death following the downregulation of RUNX3 proteinexpression Recently Wang et al reported that miR-301ais upregulated in gastric cancer and directly downregulatesRUNX3 expression [47]

Furthermore microR-34bc is considered a tumor sup-pressor and transcriptional target of p53 Based on a sched-uled follow-up study of endoscopic biopsy from noncancer-ous mucosa in the gastric body from 129 patients after cura-tive endoscopic resection of gastric cancer the cumulativeincidence of metachronous gastric cancer was significantlyhigher among patients with elevated miR-34bc methylationindicating that methylation of miR-34bc in the gastricmucosa may be a useful biomarker for predicting the risk ofmetachronous gastric cancer [48]

10 Cancer Stem Cell

Cancer stem cells have been defined as a unique subpop-ulation in tumors that possess the ability to initiate tumorgrowth and sustain tumor self-renewal Gastric cancer stemcells were first isolated and identified in 2009 Takaishi etal identified CD44 as a gastric cancer stem cell marker asCD44+ cells were able to form into spheroid colonies inserum-free media in vitro and gastric tumors after xenograftsin nude mice in vivo whereas CD44-negative sorted cellswere not [49]These cells have the ability for self-regenerationand resistance for chemotherapy- or radiation-induced celldeath Cancer stem cells-targeted therapy is a novel directionfor treating and preventing gastric cancer In our recent studytranslocated CagA fromH pylori to the epithelial cells couldaccumulate in CD44v9-expressing gastric cancer stem-likecells by escaping the autophagic degradation pathway dueto their characteristics of xCT-dependent ROS resistance[16]

The high expression of CD44 is positively correlated withmalignant transformation metastasis and relapse of gastriccancer [50] We previously reported that the recurrence rateof early gastric cancerwas significantly higher in theCD44v9-positive than the CD44v9-negative cohorts (hazard ratio218 95 CI 571ndash831) [42] CD44v9 expression in the tissueof primary gastric cancer represents a potential predictivemarker for recurrence

Additionally there is another hypothesis It is thoughtthat gastric cancer stem cells are derived from bone-marrow-derived mesenchymal stem cells When there is injury thebone-marrow-derived mesenchymal stem cells can mobilizefrom the bone marrow and participate in tissue repairVaron et al labeled bone-marrow-derived cells with greenfluorescent protein in mice model of infection withH pyloriAfter 1 year gastric glands that contained green fluorescentprotein-positive cells were detected in 90 of mice infectedwith H pylori Almost 25 of high-grade dysplastic lesionsincluded cells originating from the bone marrow [51] Theresults suggest that bone-marrow-derivedmesenchymal stemcells are the source of gastric cancer

11 Conclusion

As shown in this review molecular mechanisms of gastriccarcinogenesis have been extensively studied Alterationsin multiple genes and complex copy number and geneexpression profiles have been identified in gastric cancerover the two decades New strategies had been developedfor advanced gastric cancer treatment However the responserates remain in the 25ndash40 range across published trials andnovel molecularly directed approaches are needed

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

We would like to thank Drs Takanori Kanai and NaohisaYahagi for their comments to the final version of the paper

References

[1] K Fukase M Kato S Kikuchi et al ldquoEffect of eradicationof Helicobacter pylori on incidence of metachronous gastriccarcinoma after endoscopic resection of early gastric cancer anopen-label randomised controlled trialrdquo The Lancet vol 372no 9636 pp 392ndash397 2008

[2] H Suzuki T Nishizawa and T Hibi ldquoHelicobacter pylorieradication therapyrdquo Future Microbiology vol 5 no 4 pp 639ndash648 2010

[3] T Nishizawa H Suzuki I Nakagawa et al ldquoEarly Helicobacterpylori eradication restores sonic hedgehog expression in thegastric mucosa of mongolian gerbilsrdquo Digestion vol 79 no 2pp 99ndash108 2009

[4] M Ito S Takata M Tatsugami et al ldquoClinical preventionof gastric cancer by Helicobacter pylori eradication therapy asystematic reviewrdquo Journal of Gastroenterology vol 44 no 5pp 365ndash371 2009

[5] L Fuccio R M Zagari L H Eusebi L Laterza V Cennamoand L Ceroni ldquoMeta-analysis can Helicobacter pylori eradica-tion treatment reduce the risk for gastric cancerrdquo Annals ofInternal Medicine vol 151 no 7 pp 121ndash128 2009

[6] M Asaka M Kato S-I Takahashi et al ldquoGuidelines for themanagement of Helicobacter pylori infection in Japan 2009revised editionrdquo Helicobacter vol 15 no 1 pp 1ndash20 2010

6 BioMed Research International

[7] H Suzuki T Nishizawa H Tsugawa and T Hibi ldquoMolecularapproaches and modern clinical strategies for the managementof Helicobacter pylori infection in Japanrdquo Keio Journal ofMedicine vol 61 no 4 pp 109ndash119 2012

[8] M Suzuki S Miura M Suematsu et al ldquoHelicobacter pylori-associated ammonia production enhances neutrophil- depen-dent gastric mucosal cell injuryrdquo The American Journal ofPhysiology Gastrointestinal and Liver Physiology vol 263 no5 pp G719ndashG725 1992

[9] H Suzuki T Nishizawa H Tsugawa S Mogami and T HibildquoRoles of oxidative stress in stomach disordersrdquo Journal ofClinical Biochemistry and Nutrition vol 50 no 1 pp 35ndash392012

[10] T Ishimoto O Nagano T Yae et al ldquoCD44 variant regulatesredox status in cancer cells by stabilizing the xCT subunit ofsystem xcminus and thereby promotes tumor growthrdquo Cancer Cellvol 19 no 3 pp 387ndash400 2011

[11] R Chaturvedi M Asim M B Piazuelo et al ldquoActivation ofEGFR and ERBB2 by Helicobacter pylori results in survival ofgastric epithelial cells withDNAdamagerdquoGastroenterology vol146 no 7 pp 1739e14ndash1751e14 2014

[12] SNagini ldquoCarcinomaof the stomach a reviewof epidemiologypathogenesis molecular genetics and chemopreventionrdquoWorldJournal of Gastrointestinal Oncology vol 4 no 7 pp 156ndash1692012

[13] M Hatakeyama ldquoOncogenic mechanisms of the Helicobacterpylori CagA proteinrdquo Nature Reviews Cancer vol 4 no 9 pp688ndash694 2004

[14] MHatakeyama ldquoHelicobacter pyloriCagA and gastric cancer aparadigm for hit-and-run carcinogenesisrdquo Cell Host ampMicrobevol 15 pp 306ndash316 2014

[15] H Higashi R Tsutsumi A Fujita et al ldquoBiological activity ofthe Helicobacter pylori virulence factor CagA is determined byvariation in the tyrosine phosphorylation sitesrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 99 no 22 pp 14428ndash14433 2002

[16] H Tsugawa H Suzuki H Saya et al ldquoReactive oxygen species-induced autophagic degradation of Helicobacter pylori CagA isspecifically suppressed in cancer stem-like cellsrdquo Cell Host andMicrobe vol 12 no 6 pp 764ndash777 2012

[17] N Nagata J Akiyama H Marusawa et al ldquoEnhanced expres-sion of activation-induced cytidine deaminase in human gastricmucosa infected by Helicobacter pylori and its decrease follow-ing eradicationrdquo Journal of Gastroenterology vol 49 no 3 pp427ndash435 2014

[18] Y Matsumoto H Marusawa K Kinoshita et al ldquoHelicobacterpylori infection triggers aberrant expression of activation-induced cytidine deaminase in gastric epitheliumrdquo NatureMedicine vol 13 no 4 pp 470ndash476 2007

[19] T Shimizu H Marusawa Y Matsumoto et al ldquoAccumulationof somatic mutations in TP53 in gastric epithelium withHelicobacter pylori infectionrdquo Gastroenterology vol 147 no 2pp 407e3ndash417e3 2014

[20] W Yang A Raufi and S J Klempner ldquoTargeted therapy forgastric cancer molecular pathways and ongoing investigationsrdquoBiochimica et Biophysica Acta vol 1846 no 1 pp 232ndash237 2014

[21] H-CChenH-J ChenMAKhan et al ldquoGeneticmutations ofp53 and k-ras in gastric carcinomapatients fromHunanChinardquoTumor Biology vol 32 no 2 pp 367ndash373 2011

[22] T Hiyama K Haruma Y Kitadai et al ldquoK-ras mutation inHelicobacter pylori-associated chronic gastritis in patients with

and without gastric cancerrdquo International Journal of Cancer vol97 no 5 pp 562ndash566 2002

[23] Y-J Bang E Van Cutsem A Feyereislova et al ldquoTrastuzumabin combination with chemotherapy versus chemotherapy alonefor treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA) a phase 3 open-labelrandomised controlled trialrdquoThe Lancet vol 376 no 9742 pp687ndash697 2010

[24] F Lordick Y-K Kang H-C Chung et al ldquoCapecitabine andcisplatin with or without cetuximab for patients with previouslyuntreated advanced gastric cancer (EXPAND) a randomisedopen-label phase 3 trialrdquoThe Lancet Oncology vol 14 no 6 pp490ndash499 2013

[25] T Waddell I Chau D Cunningham et al ldquoEpirubicin oxali-platin and capecitabine with or without panitumumab forpatients with previously untreated advanced oesophagogastriccancer (REAL3) a randomised open-label phase 3 trialrdquo TheLancet Oncology vol 14 no 6 pp 481ndash489 2013

[26] T Satoh R H Xu H C Chung et al ldquoLapatinib pluspaclitaxel versus paclitaxel alone in the second-line treatment ofHER2-amplified advanced gastric cancer in Asian populationsTyTAN-a randomized phase III studyrdquo Journal of ClinicalOncology vol 32 pp 2039ndash2049 2014

[27] A Ohtsu J A Ajani Y-X Bai et al ldquoEverolimus for previouslytreated advanced gastric cancer results of the randomizeddouble-blind phase III GRANITE-1 studyrdquo Journal of ClinicalOncology vol 31 no 31 pp 3935ndash3943 2013

[28] H I Grabsch and P Tan ldquoGastric cancer pathology andunderlying molecular mechanismsrdquo Digestive Surgery vol 30no 2 pp 150ndash158 2013

[29] A Horii S Nakatsuru Y Miyoshi et al ldquoThe APC generesponsible for familial adenomatous polyposis is mutated inhuman gastric cancerrdquoCancer Research vol 52 no 11 pp 3231ndash3233 1992

[30] Y-GWenQWangC-Z ZhouG-QQiu Z-H Peng andH-M Tang ldquoMutation analysis of tumor suppressor gene PTEN inpatients with gastric carcinomas and its impact on PI3KAKTpathwayrdquo Oncology Reports vol 24 no 1 pp 89ndash95 2010

[31] X-T Hu and C He ldquoRecent progress in the study of methylatedtumor suppressor genes in gastric cancerrdquo Chinese Journal ofCancer vol 32 no 1 pp 31ndash41 2013

[32] H-L Wang P-Y Zhou P Liu and Y Zhang ldquoRole of p16gene promoter methylation in gastric carcinogenesis a meta-analysisrdquo Molecular Biology Reports vol 41 no 7 pp 4481ndash4492 2014

[33] A S L Cheng M S Li W Kang et al ldquoHelicobacter pyloricauses epigenetic dysregulation of FOXD3 to promote gastriccarcinogenesisrdquo Gastroenterology vol 144 no 1 pp 122e9ndash133e9 2013

[34] Y Hayashi M Tsujii J Wang et al ldquoCagA mediates epigeneticregulation to attenuate let-7 expression in Helicobacter pylori-related carcinogenesisrdquo Gut vol 62 no 11 pp 1536ndash1546 2013

[35] S Nanjo K Asada S Yamashita et al ldquoIdentification of gastriccancer riskmarkers that are informative in individuals with pastH pylori infectionrdquo Gastric Cancer vol 15 no 4 pp 382ndash3882012

[36] T Niwa T Toyoda T Tsukamoto A Mori M Tatematsu andT Ushijima ldquoPrevention of Helicobacter pylori-induced gastriccancers in gerbils by a DNA demethylating agentrdquo CancerPrevention Research vol 6 no 4 pp 263ndash270 2013

[37] E van Cutsem S de Haas Y-K Kang et al ldquoBevacizumabin combination with chemotherapy as first-line therapy in

BioMed Research International 7

advanced gastric cancer a biomarker evaluation from theAVAGAST randomized phase III trialrdquo Journal of ClinicalOncology vol 30 no 17 pp 2119ndash2127 2012

[38] L Shen J Li J Xu et al ldquoBevacizumab plus capecitabine andcisplatin in Chinese patients with inoperable locally advancedor metastatic gastric or gastroesophageal junction cancerrandomized double-blind phase III study (AVATAR study)rdquoGastric Cancer 2014

[39] C S Fuchs J Tomasek C J Yong et al ldquoRamucirumabmonotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (REGARD) an inter-national randomised multicentre placebo-controlled phase 3trialrdquoThe Lancet vol 383 no 9911 pp 31ndash39 2014

[40] J Li S Qin J Xu et al ldquoApatinib for chemotherapy-refractoryadvanced metastatic gastric cancer results from a randomizedplacebo-controlled parallel-arm phase II trialrdquo Journal ofClinical Oncology vol 31 no 26 pp 3219ndash3225 2013

[41] T Nishizawa and H Suzuki ldquoThe role of microRNA in gastricmalignancyrdquo International Journal of Molecular Sciences vol 14no 5 pp 9487ndash9496 2013

[42] K Hirata H Suzuki H Imaeda et al ldquoCD44 variant 9expression in primary early gastric cancer as a predictivemarkerfor recurrencerdquoBritish Journal of Cancer vol 109 no 2 pp 379ndash386 2013

[43] Y-Y Ma and H-Q Tao ldquoMicroribonucleic acids and gastriccancerrdquo Cancer Science vol 103 no 4 pp 620ndash625 2012

[44] A Shiotani N Uedo H Iishi et al ldquoH pylori eradication didnot improve dysregulation of specific oncogenic miRNAs inintestinal metaplastic glandsrdquo Journal of Gastroenterology vol47 no 9 pp 988ndash998 2012

[45] M Suzuki H Suzuki Y Minegishi K Ito T Nishizawaand T Hibi ldquoH pylori-eradication therapy increases RUNX3expression in the glandular epithelial cells in enlarged-foldgastritisrdquo Journal of Clinical Biochemistry and Nutrition vol 46no 3 pp 259ndash264 2010

[46] K W Lai K X Koh M Loh et al ldquoMicroRNA-130b regulatesthe tumour suppressor RUNX3 in gastric cancerrdquo EuropeanJournal of Cancer vol 46 no 8 pp 1456ndash1463 2010

[47] MWang C Li B Yu et al ldquoOverexpressedmiR-301a promotescell proliferation and invasion by targeting RUNX3 in gastriccancerrdquo Journal of Gastroenterology vol 48 no 9 pp 1023ndash10332013

[48] R Suzuki E Yamamoto M Nojima et al ldquoAberrant methy-lation of microRNA-34bc is a predictive marker of metach-ronous gastric cancer riskrdquo Journal of Gastroenterology vol 49no 7 pp 1135ndash1144 2014

[49] S Takaishi T Okumura S Tu et al ldquoIdentification of gastriccancer stem cells using the cell surface marker CD44rdquo StemCells vol 27 no 5 pp 1006ndash1020 2009

[50] Y Wakamatsu N Sakamoto H Z Oo et al ldquoExpression ofcancer stem cell markers ALDH1 CD44 and CD133 in primarytumor and lymph node metastasis of gastric cancerrdquo PathologyInternational vol 62 no 2 pp 112ndash119 2012

[51] C Varon P Dubus F Mazurier et al ldquoHelicobacter pyloriinfection recruits bone marrow-derived cells that participate ingastric preneoplasia in micerdquo Gastroenterology vol 142 no 2pp 281ndash291 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

2 BioMed Research International

Recent studies provided evidence that expression ofan aberrant DNARNA editing enzyme activation-inducedcytidine deaminase (AID) might be a mechanism of muta-tion accumulation in the gastric mucosa during H pylori-associated gastric carcinogenesisThe roles ofmicroRNAs areincreasingly apparent and aberrant expression of microR-NAs may contribute to the development and progression ofgastric cancer Moreover recent advances in molecular ther-apies provided a new interesting weapon to treat advancedgastric cancer through anti-human epidermal growth factorreceptor 2 (HER-2) therapies

Consequently this paper summarizes the molecularmechanism of H pylori-associated gastric carcinogenesis

2 Oxidative Stress

Oxygen-derived free radicals that are released from acti-vated neutrophils are considered potential toxic factorsthat contribute to H pylori-induced gastric mucosal injuryNeutrophils express myeloperoxidase which produces thehypochlorous anion (OClminus) OClminus reacts with the ammo-nia (NH

3

) which is produced from urea by H pylori-associated urease to yield a lipophilic highly cytotoxicoxidant monochloramine (NH

2

Cl) that freely penetratesbiological membranes to oxidize intracellular components[8] Free radicals including ROS and reactive nitrogenspecies can bind with nucleic acids turning them intomutated forms that play a role inmultistep carcinogenesis [9]

The CD44 variant (CD44v) which is a cell-surfacemarker that is associated with cancer stem-like cells inter-acts with a glutamate-cystine transporter and controls theintracellular level of reduced glutathione (GSH) [10] Humangastrointestinal cancer cells with a high level of CD44 expres-sion revealed an enhanced capacity for glutathione synthesisand defense against ROS These findings indicate that cancerstem-like cells with CD44v expression could have an ROSdefense system that results from glutathione synthesis

H pylori upregulates spermine oxidase (SMOX) in gastricepithelial cells SMOX metabolizes the polyamine spermineinto spermidine and generates H

2

O2

which causes apoptosisand DNA damage However a subpopulation of SMOXhigh

cells is resistant to apoptosis despite their high levels ofDNA damage Chaturvedi et al reported that activation ofepidermal growth factor receptor (EGFR) and erythroblasticleukemia-associated viral oncogene B (ErbB2) by H pyloriresults in survival of gastric epithelial cells with DNA damage[11]

3 CagA

Epidemiological evidence indicates that H pylori strainscontaining CagA are more virulent CagA-positive H pyloriincreases the risk of both intestinal and diffuse types ofnoncardia gastric cancer [12] The CagA protein of H pyloriwhich is delivered into gastric epithelial cells via bacterialtype IV secretion system is an oncoprotein that can inducemalignant neoplasms After the CagA protein is injectedinto the host cell cytoplasm the EPIYA (Glu-Pro-Ile-Tyr-Ala)

motif of CagA is tyrosine-phosphorylated by host Src kinasesand subsequently changes the gastric epithelial morphology[13] CagA binding to the protooncogene Src homology2-containing protein tyrosine phosphatase (SHP-2) causesaberrant activation of SHP-2 and consequently of the ERK-MAPK (mitogen-activated protein kinase) pathway whichhas been reported to play a role in carcinogenesis by inducingmitogenic responses [14] East Asian CagA that contains theEPIYA-D motif demonstrates higher affinity for SHP-2 thanWestern CagA These findings are consistent with the factthat East Asian strains dominate in countries with the highestrates of gastric cancer [15]

On the other hand CagA interacts with many signalingmolecules (eg Per-1 c-Abl Crk proteins Grb proteins andc-Met) that are important for the regulation of cell prolif-eration scattering and morphology (Figure 1) CagA thatis translocated into the host cell is degraded by autophagyand short-lived However CagA that is translocated intoCD44v9-positive gastric cancer stem-like cells which arecharacterized by ROS resistance that results from theirrich GSH content is thought to escape ROS-dependentautophagy resulting in gastric carcinogenesis [16]

4 AID

The DNARNA editing enzyme AID is a 198 amino acidprotein that directly converts cytosine into uracil (Figure 2)AID is specifically induced in germinal center B cells tocarry out somatic hypermutation and class-switch recom-bination which are two processes that are responsible forantibody diversification Because of its mutagenic potentialAID expression and activity are tightly regulated tominimizeunwanted DNA damage Surprisingly AID is also induced byinflammation and microbial infections in nonimmune cells

H pylori infection mediates aberrant AID expression ingastric mucosal epithelial cells Additionally AID expressionwas shown to be triggered by proinflammatory cytokinessuch as TNF-120572 or IL-1 and correlated with mononuclearcell infiltration and intestinal metaplasia After eradicationof H pylori the level of AID expression decreases [17]Strong evidence indicates that CagA-positive H pylori-mediated upregulation of AID resulted in the accumulationof nucleotide alterations in the TP53 tumor suppressor genein gastric cells [18] Whole-exome sequencing revealed thatsomatic mutations accumulated in various genes in inflamedgastric tissues The mutations that accumulated in gastrictumors as well as gastric mucosal tissues with H pylori-induced gastritis were predominantlyC GgtT A transitionsin GpCpXmotifs which aremarkers of cytidine deaminationthat are induced by AID [19] Increased cytidine deami-nase activity in H pylori-infected gastric tissues appears topromote the accumulation of various mutations and mightpromote gastric carcinogenesis

5 Oncogenes

Mutational activation andor amplification of several onco-genes such as ErbB KRAS PIK3CAMET andMYChas beendocumented in gastric cancer

BioMed Research International 3

Type IV secretion system

N terminalC terminal

EPIYA-motifsCagA

SHP-2

Cell motility and invasion

Cell proliferation

ERK-MAPKGrb

Par-1

C-met

Polarization defects

Figure 1 CagA and major functions CagA is delivered into gastricepithelial cells via bacterial type IV secretion system CagA interactswith many signaling molecules that are important for the regulationof cell proliferation polarity and motility

NH2

N

N

O

OO N

HN

H2O NH3

C

G G

U

T

AAID deamination DNA replication

Cytosine Uracil

Figure 2 Activation-induced cytidine deaminase (AID) as theDNARNA editing enzyme AID is induced by H pylori infectionand promotes the accumulation of various mutations

Epidermal growth factor receptor (EGFR) a memberof ErbB receptor family is involved in the regulation ofgastric mucosal cell proliferation and progression of gas-tric cancer Overexpression of ErbB1 (EGFR) and ErbB2(HER-2) is found in 27ndash64 and 6ndash34 of gastric cancerrespectively [20] Activation triggers a cascade of eventsthat involves autophosphorylation and activation of tyrosinekinase domain RasRafMAPK pathway phospholipase C-120574and phosphatidylinositol-3-kinase (PI3K)Aktmammaliantarget of rapamycin (mTOR) Ras an oncogenic smallGTPase has three isoforms namely K-Ras H-ras and N-ras Constitutive activation of Ras and Ras-related proteinspromotes cell proliferation and increase invasion and metas-tasis while inhibiting apoptotic cell death K-RAS gene wasfound to be mutated (codon-12) in intestinal-type cancer butnot in diffuse-type cancer [21] K-RAS gene mutations in Hpylori-associated chronic gastritis aremore frequent in gastriccancer patients than in cancer-free patients suggesting thatK-RAS mutation may be involved in the early stage of gastriccarcinogenesis [22]

Trastuzumab is a monoclonal antibody that binds toextracellular domain of the receptor acting by blockage ofthe HER-2 receptor cleavage inhibition of dimerization andthe induction of antibody-dependent cellular cytotoxicity(ADCC) In phase III ToGA trial the addition of trastuzumabto standard cisplatin and 5-fluorouracil improved overall

survival from 111 to 138 months in patients with HER-2 amplified gastric adenocarcinomas [23] In phase IIIEXPAND trial the addition of cetuximab (chimeric mono-clonal anti-EGFR antibody) to standard cisplatin and cape-citabine did not improve progression free survival in patientswith advanced gastric cancer [24] Similarly in phase IIIREAL-3 trial the addition of panitumumab (fully humanizedmonoclonal anti-EGFR antibody) to epirubicin oxaliplatinand capecitabine did not improve overall survival in patientswith advanced gastric adenocarcinoma [25] In additionretrospective biomarker analysis has failed to identify a clearpatient subset that would derive benefit from EGFR-directedtherapies Lapatinib is dual tyrosine kinase inhibitor active onEGFR and HER-2 In phase III TYTAN trial the addition oflapatinib to weekly paclitaxel in second-line setting improvedoverall response rate in patients with HER-2-positive gastricadenocarcinomas (odds ratio 385 95 CI 180ndash887 119875 lt0001) but did not significantly improve overall survival(lapatinib+paclitaxel 110 versus paclitaxel 89 months 119875 =0104) [26]

Phase III GRANITE-1 study evaluated the efficacy ofmTOR inhibitor everolimus compared to the best supportivecare in patients with advanced gastric cancer that progressedafter initial chemotherapy In this study median survivalwas reportedly 539 months with everolimus versus 434months with placebo (HR = 090 95 CI 075ndash108) [27]Patients in this study were not preselected with respect toPI3KAKTmTOR pathway alteration

6 Tumor-Suppressor Genes

The p53 tumor-suppressor gene the guardian of humangenome is frequently inactivated in the tissue of gastric can-cer aswell as in preneoplastic lesions by loss of heterozygosity(LOH) missense mutation or frame-shift deletions [12] Thep53 53 kDa phosphoprotein is a transcription factor forincluding DNA repair genes in response to DNA damageActivation of p53 also arrests the cell cycle to allow enoughtime for fixation of DNA damage However if DNA damageis beyond repair p53 induces apoptotic cell death Themutations of p53 have also been identified in gastric adenomaand intestinal metaplasia We have recently reported that p53downregulation due to increased MDM2-phosphorylationinduces autophagy which causes CagA oncoprotein degra-dation translocated from the bacterial body of H pylori togastric epithelial cells and then inhibits mTOR [16]

APC is a multidomain protein with binding sites fornumerous proteins including Wnt signaling pathway APCplays major role in cell adhesion cell migration spindle for-mation and chromosome segregation [28] APC mutationsare the second most frequent mutations in gastric cancerand have been observed in 30ndash40 of intestinal type cancerand in less than 2 of diffuse type cancer [29] The muta-tions of APC have also been identified in gastric adenomaand intestinal metaplasia indicating that they occur duringpreneoplastic stage of gastric cancer development LOH andmutations of phosphatase and tensin homolog (PTEN) wereobserved in gastric cancers as well as in precancerous lesions[30]

4 BioMed Research International

7 DNA Methylation

Methylation of CpG islands in a promoter region inhibitsgene transcription by interfering with transcriptional initia-tion and serves as an alternative mechanism of inactivatingtumor suppressor genes without gene mutation Amongfactors known to cause aberrant DNA methylation agingand chronic inflammation are known to promote the accu-mulation of DNA methylation H pylori infection inducesaberrant promoter methylation in tumor-suppressor genesincluding p16 LOX and CDH1 Furthermore a numberof tumor suppressor genes including hMLM1 p14 p15GSTP1 RASSF1 COX-2APC CDH4DAP-K THBS1 TIMP-3 RAR120573 MGMT CHFR DCC RUNX3 and TSLC1 areknown to be silenced by hypermethylation in gastric cancer[31] (Figure 3)

Recent meta-analysis revealed that the frequencies of p16promoter methylation in gastric cancer tissue were higherthan those of normal and adjacent tissues [Normal odds ratio(OR) = 2304 95 CI = 1355ndash3915 119875 lt 0001 AdjacentOR = 442 95 CI = 166ndash1176 119875 = 0003] Furthermoresignificant associations of p16 promoter methylation withTNM stage histologic grade invasive grade and lymph nodemetastasis are shown (TNM stage OR = 360 95 CI 217ndash598 119875 lt 0001 Histologic grade OR = 263 95 CI 155ndash445 119875 lt 0001 Invasive grade OR = 344 95 CI 168ndash706119875 = 0001 Lymph node metastasis OR = 268 95 CI 166ndash432 119875 lt 0001) [32]

Forkhead box (Fox) proteins comprise an evolutionarilyconserved family of transcriptional regulators In partic-ular FOXD3 bound directly to the promoters and acti-vated transcription of genes that encode the cell deathregulators CYFIP2 and RARB Recent methylation pro-file analyses revealed that FOXD3-mediated transcrip-tional control of tumor suppressors is deregulated by Hpylori infection-induced hypermethylation [33] Alterna-tively CagA enhanced DNA methyltransferase 3B andenhancer of zeste homologue 2 expression which resultedin the attenuation of let-7 expression by histone and DNAmethylation [34] Aberrant epigenetic silencing of let-7expression leads to Ras upregulation

DNA methylation levels of specific CpG islands are asso-ciated with risk of gastric cancer Nanjo et al identified sevennovel gastric cancer risk markers that reflect epigenomicdamage that is induced by H pylori infection and thehypermethylated CpG islands had high ORs (127ndash360) in ananalysis [35]Moreover 5-aza-21015840-deoxycytidine (5-aza-dC) isa DNA demethylating agent Niwa et al showed that 5-aza-dC treatment can prevent H pylori-induced gastric cancersin the Mongolian gerbil model [36] Removal of inducedDNA methylation andor suppression of DNA methylationinduction could become a target for prevention of chronicinflammation-associated cancers

8 Angiogenesis

Elevated concentrations of vascular endothelial growth factor(VEGF) have been described in patients with advancedgastric cancer and correlated with decreased survival VEGF

Methylation induction

Tumor suppressor gene

Promoter region

Figure 3 DNA methylation inactivates tumor suppressor geneswithout genemutation Chronic inflammation byH pylori infectioninduces aberrant promoter methylation in tumor-suppressor genes

and VEGF receptors are overexpressed in 36ndash40 of gastriccancer Phase III AVAGAST and AVATAR studies haveevaluated the addition of bevacizumab (anti-VEGF-A mon-oclonal antibody) to first-line platinum-fluoropyrimidinechemotherapy in advanced gastric cancer patients but failedto demonstrate improved survival [37 38]

Phase III REGARD trial evaluated the efficacy oframucirumab a monoclonal antibody VEGFR-2 antagonistcompared to the best supportive care (BSC) in patientswith advanced gastric cancer that progressed after previouschemotherapy Median survival was 52 months with ramu-cirumab versus 38 months with placebo (HR = 0776 95CI 0603ndash0998 119875 = 0047) [39] Based on data from thisREGARD trial the Food and Drug Administration (FDA) inUnited States approved ramucirumab as second-line therapyfor patients with advanced gastric cancer

Apatinib inhibitor of VEGF-2 showed improved pro-gression free survival and overall survival in heavily pre-treated patients withmetastatic gastric cancer in phase II trial[40] Phase III trial of apatinib is ongoing

9 MicroRNAs

MicroRNAs are noncoding RNAs that are comprised of 18ndash24 nucleotides that can posttranscriptionally downregulatevarious target genes Recent studies have shown that aconsiderable number of microRNAs are altered followinginfection with H pylori and specific microRNA deregula-tion was found to contribute to host inflammation cell-cycle progression inhibition of apoptosis cell invasion andmetastasis [41] MicroRNAs that function as oncogenesincluding miR-17 miR-21 and miR-106a were upregulatedwhereas microRNAs that function as tumor suppressorssuch asmiR-101miR-181miR-449miR-486 and let-7a weredownregulated in gastric cancer [42 43]

BioMed Research International 5

Shiotani et al reported that the expression of oncogenicmicroRNAs (miR-1792 and themiR-106b-93-25 clustermiR-21 miR-194 and miR-196) is significantly higher in theintestinal than nonintestinalmetaplasiaH pylori eradicationimproves microRNA deregulation but not in the intesti-nal metaplasia MicroRNA deregulation is not completelyreversible by eradication alone in long-term H pylori colo-nization [44]

Runt domain transcription factor 3 (RUNX3) is a tumorsuppressor that is silenced in cancer via hypermethylationof its promoter Previously we reported that H pylorieradication significantly increases RUNX3 expression ingastric epithelial cells [45] Lai et al reported that miR-130b expression is upregulated in gastric cancer and thisis inversely associated with Runx3 hypermethylation [46]miR-130b overexpression increases cell viability and reducescell death following the downregulation of RUNX3 proteinexpression Recently Wang et al reported that miR-301ais upregulated in gastric cancer and directly downregulatesRUNX3 expression [47]

Furthermore microR-34bc is considered a tumor sup-pressor and transcriptional target of p53 Based on a sched-uled follow-up study of endoscopic biopsy from noncancer-ous mucosa in the gastric body from 129 patients after cura-tive endoscopic resection of gastric cancer the cumulativeincidence of metachronous gastric cancer was significantlyhigher among patients with elevated miR-34bc methylationindicating that methylation of miR-34bc in the gastricmucosa may be a useful biomarker for predicting the risk ofmetachronous gastric cancer [48]

10 Cancer Stem Cell

Cancer stem cells have been defined as a unique subpop-ulation in tumors that possess the ability to initiate tumorgrowth and sustain tumor self-renewal Gastric cancer stemcells were first isolated and identified in 2009 Takaishi etal identified CD44 as a gastric cancer stem cell marker asCD44+ cells were able to form into spheroid colonies inserum-free media in vitro and gastric tumors after xenograftsin nude mice in vivo whereas CD44-negative sorted cellswere not [49]These cells have the ability for self-regenerationand resistance for chemotherapy- or radiation-induced celldeath Cancer stem cells-targeted therapy is a novel directionfor treating and preventing gastric cancer In our recent studytranslocated CagA fromH pylori to the epithelial cells couldaccumulate in CD44v9-expressing gastric cancer stem-likecells by escaping the autophagic degradation pathway dueto their characteristics of xCT-dependent ROS resistance[16]

The high expression of CD44 is positively correlated withmalignant transformation metastasis and relapse of gastriccancer [50] We previously reported that the recurrence rateof early gastric cancerwas significantly higher in theCD44v9-positive than the CD44v9-negative cohorts (hazard ratio218 95 CI 571ndash831) [42] CD44v9 expression in the tissueof primary gastric cancer represents a potential predictivemarker for recurrence

Additionally there is another hypothesis It is thoughtthat gastric cancer stem cells are derived from bone-marrow-derived mesenchymal stem cells When there is injury thebone-marrow-derived mesenchymal stem cells can mobilizefrom the bone marrow and participate in tissue repairVaron et al labeled bone-marrow-derived cells with greenfluorescent protein in mice model of infection withH pyloriAfter 1 year gastric glands that contained green fluorescentprotein-positive cells were detected in 90 of mice infectedwith H pylori Almost 25 of high-grade dysplastic lesionsincluded cells originating from the bone marrow [51] Theresults suggest that bone-marrow-derivedmesenchymal stemcells are the source of gastric cancer

11 Conclusion

As shown in this review molecular mechanisms of gastriccarcinogenesis have been extensively studied Alterationsin multiple genes and complex copy number and geneexpression profiles have been identified in gastric cancerover the two decades New strategies had been developedfor advanced gastric cancer treatment However the responserates remain in the 25ndash40 range across published trials andnovel molecularly directed approaches are needed

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

We would like to thank Drs Takanori Kanai and NaohisaYahagi for their comments to the final version of the paper

References

[1] K Fukase M Kato S Kikuchi et al ldquoEffect of eradicationof Helicobacter pylori on incidence of metachronous gastriccarcinoma after endoscopic resection of early gastric cancer anopen-label randomised controlled trialrdquo The Lancet vol 372no 9636 pp 392ndash397 2008

[2] H Suzuki T Nishizawa and T Hibi ldquoHelicobacter pylorieradication therapyrdquo Future Microbiology vol 5 no 4 pp 639ndash648 2010

[3] T Nishizawa H Suzuki I Nakagawa et al ldquoEarly Helicobacterpylori eradication restores sonic hedgehog expression in thegastric mucosa of mongolian gerbilsrdquo Digestion vol 79 no 2pp 99ndash108 2009

[4] M Ito S Takata M Tatsugami et al ldquoClinical preventionof gastric cancer by Helicobacter pylori eradication therapy asystematic reviewrdquo Journal of Gastroenterology vol 44 no 5pp 365ndash371 2009

[5] L Fuccio R M Zagari L H Eusebi L Laterza V Cennamoand L Ceroni ldquoMeta-analysis can Helicobacter pylori eradica-tion treatment reduce the risk for gastric cancerrdquo Annals ofInternal Medicine vol 151 no 7 pp 121ndash128 2009

[6] M Asaka M Kato S-I Takahashi et al ldquoGuidelines for themanagement of Helicobacter pylori infection in Japan 2009revised editionrdquo Helicobacter vol 15 no 1 pp 1ndash20 2010

6 BioMed Research International

[7] H Suzuki T Nishizawa H Tsugawa and T Hibi ldquoMolecularapproaches and modern clinical strategies for the managementof Helicobacter pylori infection in Japanrdquo Keio Journal ofMedicine vol 61 no 4 pp 109ndash119 2012

[8] M Suzuki S Miura M Suematsu et al ldquoHelicobacter pylori-associated ammonia production enhances neutrophil- depen-dent gastric mucosal cell injuryrdquo The American Journal ofPhysiology Gastrointestinal and Liver Physiology vol 263 no5 pp G719ndashG725 1992

[9] H Suzuki T Nishizawa H Tsugawa S Mogami and T HibildquoRoles of oxidative stress in stomach disordersrdquo Journal ofClinical Biochemistry and Nutrition vol 50 no 1 pp 35ndash392012

[10] T Ishimoto O Nagano T Yae et al ldquoCD44 variant regulatesredox status in cancer cells by stabilizing the xCT subunit ofsystem xcminus and thereby promotes tumor growthrdquo Cancer Cellvol 19 no 3 pp 387ndash400 2011

[11] R Chaturvedi M Asim M B Piazuelo et al ldquoActivation ofEGFR and ERBB2 by Helicobacter pylori results in survival ofgastric epithelial cells withDNAdamagerdquoGastroenterology vol146 no 7 pp 1739e14ndash1751e14 2014

[12] SNagini ldquoCarcinomaof the stomach a reviewof epidemiologypathogenesis molecular genetics and chemopreventionrdquoWorldJournal of Gastrointestinal Oncology vol 4 no 7 pp 156ndash1692012

[13] M Hatakeyama ldquoOncogenic mechanisms of the Helicobacterpylori CagA proteinrdquo Nature Reviews Cancer vol 4 no 9 pp688ndash694 2004

[14] MHatakeyama ldquoHelicobacter pyloriCagA and gastric cancer aparadigm for hit-and-run carcinogenesisrdquo Cell Host ampMicrobevol 15 pp 306ndash316 2014

[15] H Higashi R Tsutsumi A Fujita et al ldquoBiological activity ofthe Helicobacter pylori virulence factor CagA is determined byvariation in the tyrosine phosphorylation sitesrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 99 no 22 pp 14428ndash14433 2002

[16] H Tsugawa H Suzuki H Saya et al ldquoReactive oxygen species-induced autophagic degradation of Helicobacter pylori CagA isspecifically suppressed in cancer stem-like cellsrdquo Cell Host andMicrobe vol 12 no 6 pp 764ndash777 2012

[17] N Nagata J Akiyama H Marusawa et al ldquoEnhanced expres-sion of activation-induced cytidine deaminase in human gastricmucosa infected by Helicobacter pylori and its decrease follow-ing eradicationrdquo Journal of Gastroenterology vol 49 no 3 pp427ndash435 2014

[18] Y Matsumoto H Marusawa K Kinoshita et al ldquoHelicobacterpylori infection triggers aberrant expression of activation-induced cytidine deaminase in gastric epitheliumrdquo NatureMedicine vol 13 no 4 pp 470ndash476 2007

[19] T Shimizu H Marusawa Y Matsumoto et al ldquoAccumulationof somatic mutations in TP53 in gastric epithelium withHelicobacter pylori infectionrdquo Gastroenterology vol 147 no 2pp 407e3ndash417e3 2014

[20] W Yang A Raufi and S J Klempner ldquoTargeted therapy forgastric cancer molecular pathways and ongoing investigationsrdquoBiochimica et Biophysica Acta vol 1846 no 1 pp 232ndash237 2014

[21] H-CChenH-J ChenMAKhan et al ldquoGeneticmutations ofp53 and k-ras in gastric carcinomapatients fromHunanChinardquoTumor Biology vol 32 no 2 pp 367ndash373 2011

[22] T Hiyama K Haruma Y Kitadai et al ldquoK-ras mutation inHelicobacter pylori-associated chronic gastritis in patients with

and without gastric cancerrdquo International Journal of Cancer vol97 no 5 pp 562ndash566 2002

[23] Y-J Bang E Van Cutsem A Feyereislova et al ldquoTrastuzumabin combination with chemotherapy versus chemotherapy alonefor treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA) a phase 3 open-labelrandomised controlled trialrdquoThe Lancet vol 376 no 9742 pp687ndash697 2010

[24] F Lordick Y-K Kang H-C Chung et al ldquoCapecitabine andcisplatin with or without cetuximab for patients with previouslyuntreated advanced gastric cancer (EXPAND) a randomisedopen-label phase 3 trialrdquoThe Lancet Oncology vol 14 no 6 pp490ndash499 2013

[25] T Waddell I Chau D Cunningham et al ldquoEpirubicin oxali-platin and capecitabine with or without panitumumab forpatients with previously untreated advanced oesophagogastriccancer (REAL3) a randomised open-label phase 3 trialrdquo TheLancet Oncology vol 14 no 6 pp 481ndash489 2013

[26] T Satoh R H Xu H C Chung et al ldquoLapatinib pluspaclitaxel versus paclitaxel alone in the second-line treatment ofHER2-amplified advanced gastric cancer in Asian populationsTyTAN-a randomized phase III studyrdquo Journal of ClinicalOncology vol 32 pp 2039ndash2049 2014

[27] A Ohtsu J A Ajani Y-X Bai et al ldquoEverolimus for previouslytreated advanced gastric cancer results of the randomizeddouble-blind phase III GRANITE-1 studyrdquo Journal of ClinicalOncology vol 31 no 31 pp 3935ndash3943 2013

[28] H I Grabsch and P Tan ldquoGastric cancer pathology andunderlying molecular mechanismsrdquo Digestive Surgery vol 30no 2 pp 150ndash158 2013

[29] A Horii S Nakatsuru Y Miyoshi et al ldquoThe APC generesponsible for familial adenomatous polyposis is mutated inhuman gastric cancerrdquoCancer Research vol 52 no 11 pp 3231ndash3233 1992

[30] Y-GWenQWangC-Z ZhouG-QQiu Z-H Peng andH-M Tang ldquoMutation analysis of tumor suppressor gene PTEN inpatients with gastric carcinomas and its impact on PI3KAKTpathwayrdquo Oncology Reports vol 24 no 1 pp 89ndash95 2010

[31] X-T Hu and C He ldquoRecent progress in the study of methylatedtumor suppressor genes in gastric cancerrdquo Chinese Journal ofCancer vol 32 no 1 pp 31ndash41 2013

[32] H-L Wang P-Y Zhou P Liu and Y Zhang ldquoRole of p16gene promoter methylation in gastric carcinogenesis a meta-analysisrdquo Molecular Biology Reports vol 41 no 7 pp 4481ndash4492 2014

[33] A S L Cheng M S Li W Kang et al ldquoHelicobacter pyloricauses epigenetic dysregulation of FOXD3 to promote gastriccarcinogenesisrdquo Gastroenterology vol 144 no 1 pp 122e9ndash133e9 2013

[34] Y Hayashi M Tsujii J Wang et al ldquoCagA mediates epigeneticregulation to attenuate let-7 expression in Helicobacter pylori-related carcinogenesisrdquo Gut vol 62 no 11 pp 1536ndash1546 2013

[35] S Nanjo K Asada S Yamashita et al ldquoIdentification of gastriccancer riskmarkers that are informative in individuals with pastH pylori infectionrdquo Gastric Cancer vol 15 no 4 pp 382ndash3882012

[36] T Niwa T Toyoda T Tsukamoto A Mori M Tatematsu andT Ushijima ldquoPrevention of Helicobacter pylori-induced gastriccancers in gerbils by a DNA demethylating agentrdquo CancerPrevention Research vol 6 no 4 pp 263ndash270 2013

[37] E van Cutsem S de Haas Y-K Kang et al ldquoBevacizumabin combination with chemotherapy as first-line therapy in

BioMed Research International 7

advanced gastric cancer a biomarker evaluation from theAVAGAST randomized phase III trialrdquo Journal of ClinicalOncology vol 30 no 17 pp 2119ndash2127 2012

[38] L Shen J Li J Xu et al ldquoBevacizumab plus capecitabine andcisplatin in Chinese patients with inoperable locally advancedor metastatic gastric or gastroesophageal junction cancerrandomized double-blind phase III study (AVATAR study)rdquoGastric Cancer 2014

[39] C S Fuchs J Tomasek C J Yong et al ldquoRamucirumabmonotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (REGARD) an inter-national randomised multicentre placebo-controlled phase 3trialrdquoThe Lancet vol 383 no 9911 pp 31ndash39 2014

[40] J Li S Qin J Xu et al ldquoApatinib for chemotherapy-refractoryadvanced metastatic gastric cancer results from a randomizedplacebo-controlled parallel-arm phase II trialrdquo Journal ofClinical Oncology vol 31 no 26 pp 3219ndash3225 2013

[41] T Nishizawa and H Suzuki ldquoThe role of microRNA in gastricmalignancyrdquo International Journal of Molecular Sciences vol 14no 5 pp 9487ndash9496 2013

[42] K Hirata H Suzuki H Imaeda et al ldquoCD44 variant 9expression in primary early gastric cancer as a predictivemarkerfor recurrencerdquoBritish Journal of Cancer vol 109 no 2 pp 379ndash386 2013

[43] Y-Y Ma and H-Q Tao ldquoMicroribonucleic acids and gastriccancerrdquo Cancer Science vol 103 no 4 pp 620ndash625 2012

[44] A Shiotani N Uedo H Iishi et al ldquoH pylori eradication didnot improve dysregulation of specific oncogenic miRNAs inintestinal metaplastic glandsrdquo Journal of Gastroenterology vol47 no 9 pp 988ndash998 2012

[45] M Suzuki H Suzuki Y Minegishi K Ito T Nishizawaand T Hibi ldquoH pylori-eradication therapy increases RUNX3expression in the glandular epithelial cells in enlarged-foldgastritisrdquo Journal of Clinical Biochemistry and Nutrition vol 46no 3 pp 259ndash264 2010

[46] K W Lai K X Koh M Loh et al ldquoMicroRNA-130b regulatesthe tumour suppressor RUNX3 in gastric cancerrdquo EuropeanJournal of Cancer vol 46 no 8 pp 1456ndash1463 2010

[47] MWang C Li B Yu et al ldquoOverexpressedmiR-301a promotescell proliferation and invasion by targeting RUNX3 in gastriccancerrdquo Journal of Gastroenterology vol 48 no 9 pp 1023ndash10332013

[48] R Suzuki E Yamamoto M Nojima et al ldquoAberrant methy-lation of microRNA-34bc is a predictive marker of metach-ronous gastric cancer riskrdquo Journal of Gastroenterology vol 49no 7 pp 1135ndash1144 2014

[49] S Takaishi T Okumura S Tu et al ldquoIdentification of gastriccancer stem cells using the cell surface marker CD44rdquo StemCells vol 27 no 5 pp 1006ndash1020 2009

[50] Y Wakamatsu N Sakamoto H Z Oo et al ldquoExpression ofcancer stem cell markers ALDH1 CD44 and CD133 in primarytumor and lymph node metastasis of gastric cancerrdquo PathologyInternational vol 62 no 2 pp 112ndash119 2012

[51] C Varon P Dubus F Mazurier et al ldquoHelicobacter pyloriinfection recruits bone marrow-derived cells that participate ingastric preneoplasia in micerdquo Gastroenterology vol 142 no 2pp 281ndash291 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

BioMed Research International 3

Type IV secretion system

N terminalC terminal

EPIYA-motifsCagA

SHP-2

Cell motility and invasion

Cell proliferation

ERK-MAPKGrb

Par-1

C-met

Polarization defects

Figure 1 CagA and major functions CagA is delivered into gastricepithelial cells via bacterial type IV secretion system CagA interactswith many signaling molecules that are important for the regulationof cell proliferation polarity and motility

NH2

N

N

O

OO N

HN

H2O NH3

C

G G

U

T

AAID deamination DNA replication

Cytosine Uracil

Figure 2 Activation-induced cytidine deaminase (AID) as theDNARNA editing enzyme AID is induced by H pylori infectionand promotes the accumulation of various mutations

Epidermal growth factor receptor (EGFR) a memberof ErbB receptor family is involved in the regulation ofgastric mucosal cell proliferation and progression of gas-tric cancer Overexpression of ErbB1 (EGFR) and ErbB2(HER-2) is found in 27ndash64 and 6ndash34 of gastric cancerrespectively [20] Activation triggers a cascade of eventsthat involves autophosphorylation and activation of tyrosinekinase domain RasRafMAPK pathway phospholipase C-120574and phosphatidylinositol-3-kinase (PI3K)Aktmammaliantarget of rapamycin (mTOR) Ras an oncogenic smallGTPase has three isoforms namely K-Ras H-ras and N-ras Constitutive activation of Ras and Ras-related proteinspromotes cell proliferation and increase invasion and metas-tasis while inhibiting apoptotic cell death K-RAS gene wasfound to be mutated (codon-12) in intestinal-type cancer butnot in diffuse-type cancer [21] K-RAS gene mutations in Hpylori-associated chronic gastritis aremore frequent in gastriccancer patients than in cancer-free patients suggesting thatK-RAS mutation may be involved in the early stage of gastriccarcinogenesis [22]

Trastuzumab is a monoclonal antibody that binds toextracellular domain of the receptor acting by blockage ofthe HER-2 receptor cleavage inhibition of dimerization andthe induction of antibody-dependent cellular cytotoxicity(ADCC) In phase III ToGA trial the addition of trastuzumabto standard cisplatin and 5-fluorouracil improved overall

survival from 111 to 138 months in patients with HER-2 amplified gastric adenocarcinomas [23] In phase IIIEXPAND trial the addition of cetuximab (chimeric mono-clonal anti-EGFR antibody) to standard cisplatin and cape-citabine did not improve progression free survival in patientswith advanced gastric cancer [24] Similarly in phase IIIREAL-3 trial the addition of panitumumab (fully humanizedmonoclonal anti-EGFR antibody) to epirubicin oxaliplatinand capecitabine did not improve overall survival in patientswith advanced gastric adenocarcinoma [25] In additionretrospective biomarker analysis has failed to identify a clearpatient subset that would derive benefit from EGFR-directedtherapies Lapatinib is dual tyrosine kinase inhibitor active onEGFR and HER-2 In phase III TYTAN trial the addition oflapatinib to weekly paclitaxel in second-line setting improvedoverall response rate in patients with HER-2-positive gastricadenocarcinomas (odds ratio 385 95 CI 180ndash887 119875 lt0001) but did not significantly improve overall survival(lapatinib+paclitaxel 110 versus paclitaxel 89 months 119875 =0104) [26]

Phase III GRANITE-1 study evaluated the efficacy ofmTOR inhibitor everolimus compared to the best supportivecare in patients with advanced gastric cancer that progressedafter initial chemotherapy In this study median survivalwas reportedly 539 months with everolimus versus 434months with placebo (HR = 090 95 CI 075ndash108) [27]Patients in this study were not preselected with respect toPI3KAKTmTOR pathway alteration

6 Tumor-Suppressor Genes

The p53 tumor-suppressor gene the guardian of humangenome is frequently inactivated in the tissue of gastric can-cer aswell as in preneoplastic lesions by loss of heterozygosity(LOH) missense mutation or frame-shift deletions [12] Thep53 53 kDa phosphoprotein is a transcription factor forincluding DNA repair genes in response to DNA damageActivation of p53 also arrests the cell cycle to allow enoughtime for fixation of DNA damage However if DNA damageis beyond repair p53 induces apoptotic cell death Themutations of p53 have also been identified in gastric adenomaand intestinal metaplasia We have recently reported that p53downregulation due to increased MDM2-phosphorylationinduces autophagy which causes CagA oncoprotein degra-dation translocated from the bacterial body of H pylori togastric epithelial cells and then inhibits mTOR [16]

APC is a multidomain protein with binding sites fornumerous proteins including Wnt signaling pathway APCplays major role in cell adhesion cell migration spindle for-mation and chromosome segregation [28] APC mutationsare the second most frequent mutations in gastric cancerand have been observed in 30ndash40 of intestinal type cancerand in less than 2 of diffuse type cancer [29] The muta-tions of APC have also been identified in gastric adenomaand intestinal metaplasia indicating that they occur duringpreneoplastic stage of gastric cancer development LOH andmutations of phosphatase and tensin homolog (PTEN) wereobserved in gastric cancers as well as in precancerous lesions[30]

4 BioMed Research International

7 DNA Methylation

Methylation of CpG islands in a promoter region inhibitsgene transcription by interfering with transcriptional initia-tion and serves as an alternative mechanism of inactivatingtumor suppressor genes without gene mutation Amongfactors known to cause aberrant DNA methylation agingand chronic inflammation are known to promote the accu-mulation of DNA methylation H pylori infection inducesaberrant promoter methylation in tumor-suppressor genesincluding p16 LOX and CDH1 Furthermore a numberof tumor suppressor genes including hMLM1 p14 p15GSTP1 RASSF1 COX-2APC CDH4DAP-K THBS1 TIMP-3 RAR120573 MGMT CHFR DCC RUNX3 and TSLC1 areknown to be silenced by hypermethylation in gastric cancer[31] (Figure 3)

Recent meta-analysis revealed that the frequencies of p16promoter methylation in gastric cancer tissue were higherthan those of normal and adjacent tissues [Normal odds ratio(OR) = 2304 95 CI = 1355ndash3915 119875 lt 0001 AdjacentOR = 442 95 CI = 166ndash1176 119875 = 0003] Furthermoresignificant associations of p16 promoter methylation withTNM stage histologic grade invasive grade and lymph nodemetastasis are shown (TNM stage OR = 360 95 CI 217ndash598 119875 lt 0001 Histologic grade OR = 263 95 CI 155ndash445 119875 lt 0001 Invasive grade OR = 344 95 CI 168ndash706119875 = 0001 Lymph node metastasis OR = 268 95 CI 166ndash432 119875 lt 0001) [32]

Forkhead box (Fox) proteins comprise an evolutionarilyconserved family of transcriptional regulators In partic-ular FOXD3 bound directly to the promoters and acti-vated transcription of genes that encode the cell deathregulators CYFIP2 and RARB Recent methylation pro-file analyses revealed that FOXD3-mediated transcrip-tional control of tumor suppressors is deregulated by Hpylori infection-induced hypermethylation [33] Alterna-tively CagA enhanced DNA methyltransferase 3B andenhancer of zeste homologue 2 expression which resultedin the attenuation of let-7 expression by histone and DNAmethylation [34] Aberrant epigenetic silencing of let-7expression leads to Ras upregulation

DNA methylation levels of specific CpG islands are asso-ciated with risk of gastric cancer Nanjo et al identified sevennovel gastric cancer risk markers that reflect epigenomicdamage that is induced by H pylori infection and thehypermethylated CpG islands had high ORs (127ndash360) in ananalysis [35]Moreover 5-aza-21015840-deoxycytidine (5-aza-dC) isa DNA demethylating agent Niwa et al showed that 5-aza-dC treatment can prevent H pylori-induced gastric cancersin the Mongolian gerbil model [36] Removal of inducedDNA methylation andor suppression of DNA methylationinduction could become a target for prevention of chronicinflammation-associated cancers

8 Angiogenesis

Elevated concentrations of vascular endothelial growth factor(VEGF) have been described in patients with advancedgastric cancer and correlated with decreased survival VEGF

Methylation induction

Tumor suppressor gene

Promoter region

Figure 3 DNA methylation inactivates tumor suppressor geneswithout genemutation Chronic inflammation byH pylori infectioninduces aberrant promoter methylation in tumor-suppressor genes

and VEGF receptors are overexpressed in 36ndash40 of gastriccancer Phase III AVAGAST and AVATAR studies haveevaluated the addition of bevacizumab (anti-VEGF-A mon-oclonal antibody) to first-line platinum-fluoropyrimidinechemotherapy in advanced gastric cancer patients but failedto demonstrate improved survival [37 38]

Phase III REGARD trial evaluated the efficacy oframucirumab a monoclonal antibody VEGFR-2 antagonistcompared to the best supportive care (BSC) in patientswith advanced gastric cancer that progressed after previouschemotherapy Median survival was 52 months with ramu-cirumab versus 38 months with placebo (HR = 0776 95CI 0603ndash0998 119875 = 0047) [39] Based on data from thisREGARD trial the Food and Drug Administration (FDA) inUnited States approved ramucirumab as second-line therapyfor patients with advanced gastric cancer

Apatinib inhibitor of VEGF-2 showed improved pro-gression free survival and overall survival in heavily pre-treated patients withmetastatic gastric cancer in phase II trial[40] Phase III trial of apatinib is ongoing

9 MicroRNAs

MicroRNAs are noncoding RNAs that are comprised of 18ndash24 nucleotides that can posttranscriptionally downregulatevarious target genes Recent studies have shown that aconsiderable number of microRNAs are altered followinginfection with H pylori and specific microRNA deregula-tion was found to contribute to host inflammation cell-cycle progression inhibition of apoptosis cell invasion andmetastasis [41] MicroRNAs that function as oncogenesincluding miR-17 miR-21 and miR-106a were upregulatedwhereas microRNAs that function as tumor suppressorssuch asmiR-101miR-181miR-449miR-486 and let-7a weredownregulated in gastric cancer [42 43]

BioMed Research International 5

Shiotani et al reported that the expression of oncogenicmicroRNAs (miR-1792 and themiR-106b-93-25 clustermiR-21 miR-194 and miR-196) is significantly higher in theintestinal than nonintestinalmetaplasiaH pylori eradicationimproves microRNA deregulation but not in the intesti-nal metaplasia MicroRNA deregulation is not completelyreversible by eradication alone in long-term H pylori colo-nization [44]

Runt domain transcription factor 3 (RUNX3) is a tumorsuppressor that is silenced in cancer via hypermethylationof its promoter Previously we reported that H pylorieradication significantly increases RUNX3 expression ingastric epithelial cells [45] Lai et al reported that miR-130b expression is upregulated in gastric cancer and thisis inversely associated with Runx3 hypermethylation [46]miR-130b overexpression increases cell viability and reducescell death following the downregulation of RUNX3 proteinexpression Recently Wang et al reported that miR-301ais upregulated in gastric cancer and directly downregulatesRUNX3 expression [47]

Furthermore microR-34bc is considered a tumor sup-pressor and transcriptional target of p53 Based on a sched-uled follow-up study of endoscopic biopsy from noncancer-ous mucosa in the gastric body from 129 patients after cura-tive endoscopic resection of gastric cancer the cumulativeincidence of metachronous gastric cancer was significantlyhigher among patients with elevated miR-34bc methylationindicating that methylation of miR-34bc in the gastricmucosa may be a useful biomarker for predicting the risk ofmetachronous gastric cancer [48]

10 Cancer Stem Cell

Cancer stem cells have been defined as a unique subpop-ulation in tumors that possess the ability to initiate tumorgrowth and sustain tumor self-renewal Gastric cancer stemcells were first isolated and identified in 2009 Takaishi etal identified CD44 as a gastric cancer stem cell marker asCD44+ cells were able to form into spheroid colonies inserum-free media in vitro and gastric tumors after xenograftsin nude mice in vivo whereas CD44-negative sorted cellswere not [49]These cells have the ability for self-regenerationand resistance for chemotherapy- or radiation-induced celldeath Cancer stem cells-targeted therapy is a novel directionfor treating and preventing gastric cancer In our recent studytranslocated CagA fromH pylori to the epithelial cells couldaccumulate in CD44v9-expressing gastric cancer stem-likecells by escaping the autophagic degradation pathway dueto their characteristics of xCT-dependent ROS resistance[16]

The high expression of CD44 is positively correlated withmalignant transformation metastasis and relapse of gastriccancer [50] We previously reported that the recurrence rateof early gastric cancerwas significantly higher in theCD44v9-positive than the CD44v9-negative cohorts (hazard ratio218 95 CI 571ndash831) [42] CD44v9 expression in the tissueof primary gastric cancer represents a potential predictivemarker for recurrence

Additionally there is another hypothesis It is thoughtthat gastric cancer stem cells are derived from bone-marrow-derived mesenchymal stem cells When there is injury thebone-marrow-derived mesenchymal stem cells can mobilizefrom the bone marrow and participate in tissue repairVaron et al labeled bone-marrow-derived cells with greenfluorescent protein in mice model of infection withH pyloriAfter 1 year gastric glands that contained green fluorescentprotein-positive cells were detected in 90 of mice infectedwith H pylori Almost 25 of high-grade dysplastic lesionsincluded cells originating from the bone marrow [51] Theresults suggest that bone-marrow-derivedmesenchymal stemcells are the source of gastric cancer

11 Conclusion

As shown in this review molecular mechanisms of gastriccarcinogenesis have been extensively studied Alterationsin multiple genes and complex copy number and geneexpression profiles have been identified in gastric cancerover the two decades New strategies had been developedfor advanced gastric cancer treatment However the responserates remain in the 25ndash40 range across published trials andnovel molecularly directed approaches are needed

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

We would like to thank Drs Takanori Kanai and NaohisaYahagi for their comments to the final version of the paper

References

[1] K Fukase M Kato S Kikuchi et al ldquoEffect of eradicationof Helicobacter pylori on incidence of metachronous gastriccarcinoma after endoscopic resection of early gastric cancer anopen-label randomised controlled trialrdquo The Lancet vol 372no 9636 pp 392ndash397 2008

[2] H Suzuki T Nishizawa and T Hibi ldquoHelicobacter pylorieradication therapyrdquo Future Microbiology vol 5 no 4 pp 639ndash648 2010

[3] T Nishizawa H Suzuki I Nakagawa et al ldquoEarly Helicobacterpylori eradication restores sonic hedgehog expression in thegastric mucosa of mongolian gerbilsrdquo Digestion vol 79 no 2pp 99ndash108 2009

[4] M Ito S Takata M Tatsugami et al ldquoClinical preventionof gastric cancer by Helicobacter pylori eradication therapy asystematic reviewrdquo Journal of Gastroenterology vol 44 no 5pp 365ndash371 2009

[5] L Fuccio R M Zagari L H Eusebi L Laterza V Cennamoand L Ceroni ldquoMeta-analysis can Helicobacter pylori eradica-tion treatment reduce the risk for gastric cancerrdquo Annals ofInternal Medicine vol 151 no 7 pp 121ndash128 2009

[6] M Asaka M Kato S-I Takahashi et al ldquoGuidelines for themanagement of Helicobacter pylori infection in Japan 2009revised editionrdquo Helicobacter vol 15 no 1 pp 1ndash20 2010

6 BioMed Research International

[7] H Suzuki T Nishizawa H Tsugawa and T Hibi ldquoMolecularapproaches and modern clinical strategies for the managementof Helicobacter pylori infection in Japanrdquo Keio Journal ofMedicine vol 61 no 4 pp 109ndash119 2012

[8] M Suzuki S Miura M Suematsu et al ldquoHelicobacter pylori-associated ammonia production enhances neutrophil- depen-dent gastric mucosal cell injuryrdquo The American Journal ofPhysiology Gastrointestinal and Liver Physiology vol 263 no5 pp G719ndashG725 1992

[9] H Suzuki T Nishizawa H Tsugawa S Mogami and T HibildquoRoles of oxidative stress in stomach disordersrdquo Journal ofClinical Biochemistry and Nutrition vol 50 no 1 pp 35ndash392012

[10] T Ishimoto O Nagano T Yae et al ldquoCD44 variant regulatesredox status in cancer cells by stabilizing the xCT subunit ofsystem xcminus and thereby promotes tumor growthrdquo Cancer Cellvol 19 no 3 pp 387ndash400 2011

[11] R Chaturvedi M Asim M B Piazuelo et al ldquoActivation ofEGFR and ERBB2 by Helicobacter pylori results in survival ofgastric epithelial cells withDNAdamagerdquoGastroenterology vol146 no 7 pp 1739e14ndash1751e14 2014

[12] SNagini ldquoCarcinomaof the stomach a reviewof epidemiologypathogenesis molecular genetics and chemopreventionrdquoWorldJournal of Gastrointestinal Oncology vol 4 no 7 pp 156ndash1692012

[13] M Hatakeyama ldquoOncogenic mechanisms of the Helicobacterpylori CagA proteinrdquo Nature Reviews Cancer vol 4 no 9 pp688ndash694 2004

[14] MHatakeyama ldquoHelicobacter pyloriCagA and gastric cancer aparadigm for hit-and-run carcinogenesisrdquo Cell Host ampMicrobevol 15 pp 306ndash316 2014

[15] H Higashi R Tsutsumi A Fujita et al ldquoBiological activity ofthe Helicobacter pylori virulence factor CagA is determined byvariation in the tyrosine phosphorylation sitesrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 99 no 22 pp 14428ndash14433 2002

[16] H Tsugawa H Suzuki H Saya et al ldquoReactive oxygen species-induced autophagic degradation of Helicobacter pylori CagA isspecifically suppressed in cancer stem-like cellsrdquo Cell Host andMicrobe vol 12 no 6 pp 764ndash777 2012

[17] N Nagata J Akiyama H Marusawa et al ldquoEnhanced expres-sion of activation-induced cytidine deaminase in human gastricmucosa infected by Helicobacter pylori and its decrease follow-ing eradicationrdquo Journal of Gastroenterology vol 49 no 3 pp427ndash435 2014

[18] Y Matsumoto H Marusawa K Kinoshita et al ldquoHelicobacterpylori infection triggers aberrant expression of activation-induced cytidine deaminase in gastric epitheliumrdquo NatureMedicine vol 13 no 4 pp 470ndash476 2007

[19] T Shimizu H Marusawa Y Matsumoto et al ldquoAccumulationof somatic mutations in TP53 in gastric epithelium withHelicobacter pylori infectionrdquo Gastroenterology vol 147 no 2pp 407e3ndash417e3 2014

[20] W Yang A Raufi and S J Klempner ldquoTargeted therapy forgastric cancer molecular pathways and ongoing investigationsrdquoBiochimica et Biophysica Acta vol 1846 no 1 pp 232ndash237 2014

[21] H-CChenH-J ChenMAKhan et al ldquoGeneticmutations ofp53 and k-ras in gastric carcinomapatients fromHunanChinardquoTumor Biology vol 32 no 2 pp 367ndash373 2011

[22] T Hiyama K Haruma Y Kitadai et al ldquoK-ras mutation inHelicobacter pylori-associated chronic gastritis in patients with

and without gastric cancerrdquo International Journal of Cancer vol97 no 5 pp 562ndash566 2002

[23] Y-J Bang E Van Cutsem A Feyereislova et al ldquoTrastuzumabin combination with chemotherapy versus chemotherapy alonefor treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA) a phase 3 open-labelrandomised controlled trialrdquoThe Lancet vol 376 no 9742 pp687ndash697 2010

[24] F Lordick Y-K Kang H-C Chung et al ldquoCapecitabine andcisplatin with or without cetuximab for patients with previouslyuntreated advanced gastric cancer (EXPAND) a randomisedopen-label phase 3 trialrdquoThe Lancet Oncology vol 14 no 6 pp490ndash499 2013

[25] T Waddell I Chau D Cunningham et al ldquoEpirubicin oxali-platin and capecitabine with or without panitumumab forpatients with previously untreated advanced oesophagogastriccancer (REAL3) a randomised open-label phase 3 trialrdquo TheLancet Oncology vol 14 no 6 pp 481ndash489 2013

[26] T Satoh R H Xu H C Chung et al ldquoLapatinib pluspaclitaxel versus paclitaxel alone in the second-line treatment ofHER2-amplified advanced gastric cancer in Asian populationsTyTAN-a randomized phase III studyrdquo Journal of ClinicalOncology vol 32 pp 2039ndash2049 2014

[27] A Ohtsu J A Ajani Y-X Bai et al ldquoEverolimus for previouslytreated advanced gastric cancer results of the randomizeddouble-blind phase III GRANITE-1 studyrdquo Journal of ClinicalOncology vol 31 no 31 pp 3935ndash3943 2013

[28] H I Grabsch and P Tan ldquoGastric cancer pathology andunderlying molecular mechanismsrdquo Digestive Surgery vol 30no 2 pp 150ndash158 2013

[29] A Horii S Nakatsuru Y Miyoshi et al ldquoThe APC generesponsible for familial adenomatous polyposis is mutated inhuman gastric cancerrdquoCancer Research vol 52 no 11 pp 3231ndash3233 1992

[30] Y-GWenQWangC-Z ZhouG-QQiu Z-H Peng andH-M Tang ldquoMutation analysis of tumor suppressor gene PTEN inpatients with gastric carcinomas and its impact on PI3KAKTpathwayrdquo Oncology Reports vol 24 no 1 pp 89ndash95 2010

[31] X-T Hu and C He ldquoRecent progress in the study of methylatedtumor suppressor genes in gastric cancerrdquo Chinese Journal ofCancer vol 32 no 1 pp 31ndash41 2013

[32] H-L Wang P-Y Zhou P Liu and Y Zhang ldquoRole of p16gene promoter methylation in gastric carcinogenesis a meta-analysisrdquo Molecular Biology Reports vol 41 no 7 pp 4481ndash4492 2014

[33] A S L Cheng M S Li W Kang et al ldquoHelicobacter pyloricauses epigenetic dysregulation of FOXD3 to promote gastriccarcinogenesisrdquo Gastroenterology vol 144 no 1 pp 122e9ndash133e9 2013

[34] Y Hayashi M Tsujii J Wang et al ldquoCagA mediates epigeneticregulation to attenuate let-7 expression in Helicobacter pylori-related carcinogenesisrdquo Gut vol 62 no 11 pp 1536ndash1546 2013

[35] S Nanjo K Asada S Yamashita et al ldquoIdentification of gastriccancer riskmarkers that are informative in individuals with pastH pylori infectionrdquo Gastric Cancer vol 15 no 4 pp 382ndash3882012

[36] T Niwa T Toyoda T Tsukamoto A Mori M Tatematsu andT Ushijima ldquoPrevention of Helicobacter pylori-induced gastriccancers in gerbils by a DNA demethylating agentrdquo CancerPrevention Research vol 6 no 4 pp 263ndash270 2013

[37] E van Cutsem S de Haas Y-K Kang et al ldquoBevacizumabin combination with chemotherapy as first-line therapy in

BioMed Research International 7

advanced gastric cancer a biomarker evaluation from theAVAGAST randomized phase III trialrdquo Journal of ClinicalOncology vol 30 no 17 pp 2119ndash2127 2012

[38] L Shen J Li J Xu et al ldquoBevacizumab plus capecitabine andcisplatin in Chinese patients with inoperable locally advancedor metastatic gastric or gastroesophageal junction cancerrandomized double-blind phase III study (AVATAR study)rdquoGastric Cancer 2014

[39] C S Fuchs J Tomasek C J Yong et al ldquoRamucirumabmonotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (REGARD) an inter-national randomised multicentre placebo-controlled phase 3trialrdquoThe Lancet vol 383 no 9911 pp 31ndash39 2014

[40] J Li S Qin J Xu et al ldquoApatinib for chemotherapy-refractoryadvanced metastatic gastric cancer results from a randomizedplacebo-controlled parallel-arm phase II trialrdquo Journal ofClinical Oncology vol 31 no 26 pp 3219ndash3225 2013

[41] T Nishizawa and H Suzuki ldquoThe role of microRNA in gastricmalignancyrdquo International Journal of Molecular Sciences vol 14no 5 pp 9487ndash9496 2013

[42] K Hirata H Suzuki H Imaeda et al ldquoCD44 variant 9expression in primary early gastric cancer as a predictivemarkerfor recurrencerdquoBritish Journal of Cancer vol 109 no 2 pp 379ndash386 2013

[43] Y-Y Ma and H-Q Tao ldquoMicroribonucleic acids and gastriccancerrdquo Cancer Science vol 103 no 4 pp 620ndash625 2012

[44] A Shiotani N Uedo H Iishi et al ldquoH pylori eradication didnot improve dysregulation of specific oncogenic miRNAs inintestinal metaplastic glandsrdquo Journal of Gastroenterology vol47 no 9 pp 988ndash998 2012

[45] M Suzuki H Suzuki Y Minegishi K Ito T Nishizawaand T Hibi ldquoH pylori-eradication therapy increases RUNX3expression in the glandular epithelial cells in enlarged-foldgastritisrdquo Journal of Clinical Biochemistry and Nutrition vol 46no 3 pp 259ndash264 2010

[46] K W Lai K X Koh M Loh et al ldquoMicroRNA-130b regulatesthe tumour suppressor RUNX3 in gastric cancerrdquo EuropeanJournal of Cancer vol 46 no 8 pp 1456ndash1463 2010

[47] MWang C Li B Yu et al ldquoOverexpressedmiR-301a promotescell proliferation and invasion by targeting RUNX3 in gastriccancerrdquo Journal of Gastroenterology vol 48 no 9 pp 1023ndash10332013

[48] R Suzuki E Yamamoto M Nojima et al ldquoAberrant methy-lation of microRNA-34bc is a predictive marker of metach-ronous gastric cancer riskrdquo Journal of Gastroenterology vol 49no 7 pp 1135ndash1144 2014

[49] S Takaishi T Okumura S Tu et al ldquoIdentification of gastriccancer stem cells using the cell surface marker CD44rdquo StemCells vol 27 no 5 pp 1006ndash1020 2009

[50] Y Wakamatsu N Sakamoto H Z Oo et al ldquoExpression ofcancer stem cell markers ALDH1 CD44 and CD133 in primarytumor and lymph node metastasis of gastric cancerrdquo PathologyInternational vol 62 no 2 pp 112ndash119 2012

[51] C Varon P Dubus F Mazurier et al ldquoHelicobacter pyloriinfection recruits bone marrow-derived cells that participate ingastric preneoplasia in micerdquo Gastroenterology vol 142 no 2pp 281ndash291 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

4 BioMed Research International

7 DNA Methylation

Methylation of CpG islands in a promoter region inhibitsgene transcription by interfering with transcriptional initia-tion and serves as an alternative mechanism of inactivatingtumor suppressor genes without gene mutation Amongfactors known to cause aberrant DNA methylation agingand chronic inflammation are known to promote the accu-mulation of DNA methylation H pylori infection inducesaberrant promoter methylation in tumor-suppressor genesincluding p16 LOX and CDH1 Furthermore a numberof tumor suppressor genes including hMLM1 p14 p15GSTP1 RASSF1 COX-2APC CDH4DAP-K THBS1 TIMP-3 RAR120573 MGMT CHFR DCC RUNX3 and TSLC1 areknown to be silenced by hypermethylation in gastric cancer[31] (Figure 3)

Recent meta-analysis revealed that the frequencies of p16promoter methylation in gastric cancer tissue were higherthan those of normal and adjacent tissues [Normal odds ratio(OR) = 2304 95 CI = 1355ndash3915 119875 lt 0001 AdjacentOR = 442 95 CI = 166ndash1176 119875 = 0003] Furthermoresignificant associations of p16 promoter methylation withTNM stage histologic grade invasive grade and lymph nodemetastasis are shown (TNM stage OR = 360 95 CI 217ndash598 119875 lt 0001 Histologic grade OR = 263 95 CI 155ndash445 119875 lt 0001 Invasive grade OR = 344 95 CI 168ndash706119875 = 0001 Lymph node metastasis OR = 268 95 CI 166ndash432 119875 lt 0001) [32]

Forkhead box (Fox) proteins comprise an evolutionarilyconserved family of transcriptional regulators In partic-ular FOXD3 bound directly to the promoters and acti-vated transcription of genes that encode the cell deathregulators CYFIP2 and RARB Recent methylation pro-file analyses revealed that FOXD3-mediated transcrip-tional control of tumor suppressors is deregulated by Hpylori infection-induced hypermethylation [33] Alterna-tively CagA enhanced DNA methyltransferase 3B andenhancer of zeste homologue 2 expression which resultedin the attenuation of let-7 expression by histone and DNAmethylation [34] Aberrant epigenetic silencing of let-7expression leads to Ras upregulation

DNA methylation levels of specific CpG islands are asso-ciated with risk of gastric cancer Nanjo et al identified sevennovel gastric cancer risk markers that reflect epigenomicdamage that is induced by H pylori infection and thehypermethylated CpG islands had high ORs (127ndash360) in ananalysis [35]Moreover 5-aza-21015840-deoxycytidine (5-aza-dC) isa DNA demethylating agent Niwa et al showed that 5-aza-dC treatment can prevent H pylori-induced gastric cancersin the Mongolian gerbil model [36] Removal of inducedDNA methylation andor suppression of DNA methylationinduction could become a target for prevention of chronicinflammation-associated cancers

8 Angiogenesis

Elevated concentrations of vascular endothelial growth factor(VEGF) have been described in patients with advancedgastric cancer and correlated with decreased survival VEGF

Methylation induction

Tumor suppressor gene

Promoter region

Figure 3 DNA methylation inactivates tumor suppressor geneswithout genemutation Chronic inflammation byH pylori infectioninduces aberrant promoter methylation in tumor-suppressor genes

and VEGF receptors are overexpressed in 36ndash40 of gastriccancer Phase III AVAGAST and AVATAR studies haveevaluated the addition of bevacizumab (anti-VEGF-A mon-oclonal antibody) to first-line platinum-fluoropyrimidinechemotherapy in advanced gastric cancer patients but failedto demonstrate improved survival [37 38]

Phase III REGARD trial evaluated the efficacy oframucirumab a monoclonal antibody VEGFR-2 antagonistcompared to the best supportive care (BSC) in patientswith advanced gastric cancer that progressed after previouschemotherapy Median survival was 52 months with ramu-cirumab versus 38 months with placebo (HR = 0776 95CI 0603ndash0998 119875 = 0047) [39] Based on data from thisREGARD trial the Food and Drug Administration (FDA) inUnited States approved ramucirumab as second-line therapyfor patients with advanced gastric cancer

Apatinib inhibitor of VEGF-2 showed improved pro-gression free survival and overall survival in heavily pre-treated patients withmetastatic gastric cancer in phase II trial[40] Phase III trial of apatinib is ongoing

9 MicroRNAs

MicroRNAs are noncoding RNAs that are comprised of 18ndash24 nucleotides that can posttranscriptionally downregulatevarious target genes Recent studies have shown that aconsiderable number of microRNAs are altered followinginfection with H pylori and specific microRNA deregula-tion was found to contribute to host inflammation cell-cycle progression inhibition of apoptosis cell invasion andmetastasis [41] MicroRNAs that function as oncogenesincluding miR-17 miR-21 and miR-106a were upregulatedwhereas microRNAs that function as tumor suppressorssuch asmiR-101miR-181miR-449miR-486 and let-7a weredownregulated in gastric cancer [42 43]

BioMed Research International 5

Shiotani et al reported that the expression of oncogenicmicroRNAs (miR-1792 and themiR-106b-93-25 clustermiR-21 miR-194 and miR-196) is significantly higher in theintestinal than nonintestinalmetaplasiaH pylori eradicationimproves microRNA deregulation but not in the intesti-nal metaplasia MicroRNA deregulation is not completelyreversible by eradication alone in long-term H pylori colo-nization [44]

Runt domain transcription factor 3 (RUNX3) is a tumorsuppressor that is silenced in cancer via hypermethylationof its promoter Previously we reported that H pylorieradication significantly increases RUNX3 expression ingastric epithelial cells [45] Lai et al reported that miR-130b expression is upregulated in gastric cancer and thisis inversely associated with Runx3 hypermethylation [46]miR-130b overexpression increases cell viability and reducescell death following the downregulation of RUNX3 proteinexpression Recently Wang et al reported that miR-301ais upregulated in gastric cancer and directly downregulatesRUNX3 expression [47]

Furthermore microR-34bc is considered a tumor sup-pressor and transcriptional target of p53 Based on a sched-uled follow-up study of endoscopic biopsy from noncancer-ous mucosa in the gastric body from 129 patients after cura-tive endoscopic resection of gastric cancer the cumulativeincidence of metachronous gastric cancer was significantlyhigher among patients with elevated miR-34bc methylationindicating that methylation of miR-34bc in the gastricmucosa may be a useful biomarker for predicting the risk ofmetachronous gastric cancer [48]

10 Cancer Stem Cell

Cancer stem cells have been defined as a unique subpop-ulation in tumors that possess the ability to initiate tumorgrowth and sustain tumor self-renewal Gastric cancer stemcells were first isolated and identified in 2009 Takaishi etal identified CD44 as a gastric cancer stem cell marker asCD44+ cells were able to form into spheroid colonies inserum-free media in vitro and gastric tumors after xenograftsin nude mice in vivo whereas CD44-negative sorted cellswere not [49]These cells have the ability for self-regenerationand resistance for chemotherapy- or radiation-induced celldeath Cancer stem cells-targeted therapy is a novel directionfor treating and preventing gastric cancer In our recent studytranslocated CagA fromH pylori to the epithelial cells couldaccumulate in CD44v9-expressing gastric cancer stem-likecells by escaping the autophagic degradation pathway dueto their characteristics of xCT-dependent ROS resistance[16]

The high expression of CD44 is positively correlated withmalignant transformation metastasis and relapse of gastriccancer [50] We previously reported that the recurrence rateof early gastric cancerwas significantly higher in theCD44v9-positive than the CD44v9-negative cohorts (hazard ratio218 95 CI 571ndash831) [42] CD44v9 expression in the tissueof primary gastric cancer represents a potential predictivemarker for recurrence

Additionally there is another hypothesis It is thoughtthat gastric cancer stem cells are derived from bone-marrow-derived mesenchymal stem cells When there is injury thebone-marrow-derived mesenchymal stem cells can mobilizefrom the bone marrow and participate in tissue repairVaron et al labeled bone-marrow-derived cells with greenfluorescent protein in mice model of infection withH pyloriAfter 1 year gastric glands that contained green fluorescentprotein-positive cells were detected in 90 of mice infectedwith H pylori Almost 25 of high-grade dysplastic lesionsincluded cells originating from the bone marrow [51] Theresults suggest that bone-marrow-derivedmesenchymal stemcells are the source of gastric cancer

11 Conclusion

As shown in this review molecular mechanisms of gastriccarcinogenesis have been extensively studied Alterationsin multiple genes and complex copy number and geneexpression profiles have been identified in gastric cancerover the two decades New strategies had been developedfor advanced gastric cancer treatment However the responserates remain in the 25ndash40 range across published trials andnovel molecularly directed approaches are needed

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

We would like to thank Drs Takanori Kanai and NaohisaYahagi for their comments to the final version of the paper

References

[1] K Fukase M Kato S Kikuchi et al ldquoEffect of eradicationof Helicobacter pylori on incidence of metachronous gastriccarcinoma after endoscopic resection of early gastric cancer anopen-label randomised controlled trialrdquo The Lancet vol 372no 9636 pp 392ndash397 2008

[2] H Suzuki T Nishizawa and T Hibi ldquoHelicobacter pylorieradication therapyrdquo Future Microbiology vol 5 no 4 pp 639ndash648 2010

[3] T Nishizawa H Suzuki I Nakagawa et al ldquoEarly Helicobacterpylori eradication restores sonic hedgehog expression in thegastric mucosa of mongolian gerbilsrdquo Digestion vol 79 no 2pp 99ndash108 2009

[4] M Ito S Takata M Tatsugami et al ldquoClinical preventionof gastric cancer by Helicobacter pylori eradication therapy asystematic reviewrdquo Journal of Gastroenterology vol 44 no 5pp 365ndash371 2009

[5] L Fuccio R M Zagari L H Eusebi L Laterza V Cennamoand L Ceroni ldquoMeta-analysis can Helicobacter pylori eradica-tion treatment reduce the risk for gastric cancerrdquo Annals ofInternal Medicine vol 151 no 7 pp 121ndash128 2009

[6] M Asaka M Kato S-I Takahashi et al ldquoGuidelines for themanagement of Helicobacter pylori infection in Japan 2009revised editionrdquo Helicobacter vol 15 no 1 pp 1ndash20 2010

6 BioMed Research International

[7] H Suzuki T Nishizawa H Tsugawa and T Hibi ldquoMolecularapproaches and modern clinical strategies for the managementof Helicobacter pylori infection in Japanrdquo Keio Journal ofMedicine vol 61 no 4 pp 109ndash119 2012

[8] M Suzuki S Miura M Suematsu et al ldquoHelicobacter pylori-associated ammonia production enhances neutrophil- depen-dent gastric mucosal cell injuryrdquo The American Journal ofPhysiology Gastrointestinal and Liver Physiology vol 263 no5 pp G719ndashG725 1992

[9] H Suzuki T Nishizawa H Tsugawa S Mogami and T HibildquoRoles of oxidative stress in stomach disordersrdquo Journal ofClinical Biochemistry and Nutrition vol 50 no 1 pp 35ndash392012

[10] T Ishimoto O Nagano T Yae et al ldquoCD44 variant regulatesredox status in cancer cells by stabilizing the xCT subunit ofsystem xcminus and thereby promotes tumor growthrdquo Cancer Cellvol 19 no 3 pp 387ndash400 2011

[11] R Chaturvedi M Asim M B Piazuelo et al ldquoActivation ofEGFR and ERBB2 by Helicobacter pylori results in survival ofgastric epithelial cells withDNAdamagerdquoGastroenterology vol146 no 7 pp 1739e14ndash1751e14 2014

[12] SNagini ldquoCarcinomaof the stomach a reviewof epidemiologypathogenesis molecular genetics and chemopreventionrdquoWorldJournal of Gastrointestinal Oncology vol 4 no 7 pp 156ndash1692012

[13] M Hatakeyama ldquoOncogenic mechanisms of the Helicobacterpylori CagA proteinrdquo Nature Reviews Cancer vol 4 no 9 pp688ndash694 2004

[14] MHatakeyama ldquoHelicobacter pyloriCagA and gastric cancer aparadigm for hit-and-run carcinogenesisrdquo Cell Host ampMicrobevol 15 pp 306ndash316 2014

[15] H Higashi R Tsutsumi A Fujita et al ldquoBiological activity ofthe Helicobacter pylori virulence factor CagA is determined byvariation in the tyrosine phosphorylation sitesrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 99 no 22 pp 14428ndash14433 2002

[16] H Tsugawa H Suzuki H Saya et al ldquoReactive oxygen species-induced autophagic degradation of Helicobacter pylori CagA isspecifically suppressed in cancer stem-like cellsrdquo Cell Host andMicrobe vol 12 no 6 pp 764ndash777 2012

[17] N Nagata J Akiyama H Marusawa et al ldquoEnhanced expres-sion of activation-induced cytidine deaminase in human gastricmucosa infected by Helicobacter pylori and its decrease follow-ing eradicationrdquo Journal of Gastroenterology vol 49 no 3 pp427ndash435 2014

[18] Y Matsumoto H Marusawa K Kinoshita et al ldquoHelicobacterpylori infection triggers aberrant expression of activation-induced cytidine deaminase in gastric epitheliumrdquo NatureMedicine vol 13 no 4 pp 470ndash476 2007

[19] T Shimizu H Marusawa Y Matsumoto et al ldquoAccumulationof somatic mutations in TP53 in gastric epithelium withHelicobacter pylori infectionrdquo Gastroenterology vol 147 no 2pp 407e3ndash417e3 2014

[20] W Yang A Raufi and S J Klempner ldquoTargeted therapy forgastric cancer molecular pathways and ongoing investigationsrdquoBiochimica et Biophysica Acta vol 1846 no 1 pp 232ndash237 2014

[21] H-CChenH-J ChenMAKhan et al ldquoGeneticmutations ofp53 and k-ras in gastric carcinomapatients fromHunanChinardquoTumor Biology vol 32 no 2 pp 367ndash373 2011

[22] T Hiyama K Haruma Y Kitadai et al ldquoK-ras mutation inHelicobacter pylori-associated chronic gastritis in patients with

and without gastric cancerrdquo International Journal of Cancer vol97 no 5 pp 562ndash566 2002

[23] Y-J Bang E Van Cutsem A Feyereislova et al ldquoTrastuzumabin combination with chemotherapy versus chemotherapy alonefor treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA) a phase 3 open-labelrandomised controlled trialrdquoThe Lancet vol 376 no 9742 pp687ndash697 2010

[24] F Lordick Y-K Kang H-C Chung et al ldquoCapecitabine andcisplatin with or without cetuximab for patients with previouslyuntreated advanced gastric cancer (EXPAND) a randomisedopen-label phase 3 trialrdquoThe Lancet Oncology vol 14 no 6 pp490ndash499 2013

[25] T Waddell I Chau D Cunningham et al ldquoEpirubicin oxali-platin and capecitabine with or without panitumumab forpatients with previously untreated advanced oesophagogastriccancer (REAL3) a randomised open-label phase 3 trialrdquo TheLancet Oncology vol 14 no 6 pp 481ndash489 2013

[26] T Satoh R H Xu H C Chung et al ldquoLapatinib pluspaclitaxel versus paclitaxel alone in the second-line treatment ofHER2-amplified advanced gastric cancer in Asian populationsTyTAN-a randomized phase III studyrdquo Journal of ClinicalOncology vol 32 pp 2039ndash2049 2014

[27] A Ohtsu J A Ajani Y-X Bai et al ldquoEverolimus for previouslytreated advanced gastric cancer results of the randomizeddouble-blind phase III GRANITE-1 studyrdquo Journal of ClinicalOncology vol 31 no 31 pp 3935ndash3943 2013

[28] H I Grabsch and P Tan ldquoGastric cancer pathology andunderlying molecular mechanismsrdquo Digestive Surgery vol 30no 2 pp 150ndash158 2013

[29] A Horii S Nakatsuru Y Miyoshi et al ldquoThe APC generesponsible for familial adenomatous polyposis is mutated inhuman gastric cancerrdquoCancer Research vol 52 no 11 pp 3231ndash3233 1992

[30] Y-GWenQWangC-Z ZhouG-QQiu Z-H Peng andH-M Tang ldquoMutation analysis of tumor suppressor gene PTEN inpatients with gastric carcinomas and its impact on PI3KAKTpathwayrdquo Oncology Reports vol 24 no 1 pp 89ndash95 2010

[31] X-T Hu and C He ldquoRecent progress in the study of methylatedtumor suppressor genes in gastric cancerrdquo Chinese Journal ofCancer vol 32 no 1 pp 31ndash41 2013

[32] H-L Wang P-Y Zhou P Liu and Y Zhang ldquoRole of p16gene promoter methylation in gastric carcinogenesis a meta-analysisrdquo Molecular Biology Reports vol 41 no 7 pp 4481ndash4492 2014

[33] A S L Cheng M S Li W Kang et al ldquoHelicobacter pyloricauses epigenetic dysregulation of FOXD3 to promote gastriccarcinogenesisrdquo Gastroenterology vol 144 no 1 pp 122e9ndash133e9 2013

[34] Y Hayashi M Tsujii J Wang et al ldquoCagA mediates epigeneticregulation to attenuate let-7 expression in Helicobacter pylori-related carcinogenesisrdquo Gut vol 62 no 11 pp 1536ndash1546 2013

[35] S Nanjo K Asada S Yamashita et al ldquoIdentification of gastriccancer riskmarkers that are informative in individuals with pastH pylori infectionrdquo Gastric Cancer vol 15 no 4 pp 382ndash3882012

[36] T Niwa T Toyoda T Tsukamoto A Mori M Tatematsu andT Ushijima ldquoPrevention of Helicobacter pylori-induced gastriccancers in gerbils by a DNA demethylating agentrdquo CancerPrevention Research vol 6 no 4 pp 263ndash270 2013

[37] E van Cutsem S de Haas Y-K Kang et al ldquoBevacizumabin combination with chemotherapy as first-line therapy in

BioMed Research International 7

advanced gastric cancer a biomarker evaluation from theAVAGAST randomized phase III trialrdquo Journal of ClinicalOncology vol 30 no 17 pp 2119ndash2127 2012

[38] L Shen J Li J Xu et al ldquoBevacizumab plus capecitabine andcisplatin in Chinese patients with inoperable locally advancedor metastatic gastric or gastroesophageal junction cancerrandomized double-blind phase III study (AVATAR study)rdquoGastric Cancer 2014

[39] C S Fuchs J Tomasek C J Yong et al ldquoRamucirumabmonotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (REGARD) an inter-national randomised multicentre placebo-controlled phase 3trialrdquoThe Lancet vol 383 no 9911 pp 31ndash39 2014

[40] J Li S Qin J Xu et al ldquoApatinib for chemotherapy-refractoryadvanced metastatic gastric cancer results from a randomizedplacebo-controlled parallel-arm phase II trialrdquo Journal ofClinical Oncology vol 31 no 26 pp 3219ndash3225 2013

[41] T Nishizawa and H Suzuki ldquoThe role of microRNA in gastricmalignancyrdquo International Journal of Molecular Sciences vol 14no 5 pp 9487ndash9496 2013

[42] K Hirata H Suzuki H Imaeda et al ldquoCD44 variant 9expression in primary early gastric cancer as a predictivemarkerfor recurrencerdquoBritish Journal of Cancer vol 109 no 2 pp 379ndash386 2013

[43] Y-Y Ma and H-Q Tao ldquoMicroribonucleic acids and gastriccancerrdquo Cancer Science vol 103 no 4 pp 620ndash625 2012

[44] A Shiotani N Uedo H Iishi et al ldquoH pylori eradication didnot improve dysregulation of specific oncogenic miRNAs inintestinal metaplastic glandsrdquo Journal of Gastroenterology vol47 no 9 pp 988ndash998 2012

[45] M Suzuki H Suzuki Y Minegishi K Ito T Nishizawaand T Hibi ldquoH pylori-eradication therapy increases RUNX3expression in the glandular epithelial cells in enlarged-foldgastritisrdquo Journal of Clinical Biochemistry and Nutrition vol 46no 3 pp 259ndash264 2010

[46] K W Lai K X Koh M Loh et al ldquoMicroRNA-130b regulatesthe tumour suppressor RUNX3 in gastric cancerrdquo EuropeanJournal of Cancer vol 46 no 8 pp 1456ndash1463 2010

[47] MWang C Li B Yu et al ldquoOverexpressedmiR-301a promotescell proliferation and invasion by targeting RUNX3 in gastriccancerrdquo Journal of Gastroenterology vol 48 no 9 pp 1023ndash10332013

[48] R Suzuki E Yamamoto M Nojima et al ldquoAberrant methy-lation of microRNA-34bc is a predictive marker of metach-ronous gastric cancer riskrdquo Journal of Gastroenterology vol 49no 7 pp 1135ndash1144 2014

[49] S Takaishi T Okumura S Tu et al ldquoIdentification of gastriccancer stem cells using the cell surface marker CD44rdquo StemCells vol 27 no 5 pp 1006ndash1020 2009

[50] Y Wakamatsu N Sakamoto H Z Oo et al ldquoExpression ofcancer stem cell markers ALDH1 CD44 and CD133 in primarytumor and lymph node metastasis of gastric cancerrdquo PathologyInternational vol 62 no 2 pp 112ndash119 2012

[51] C Varon P Dubus F Mazurier et al ldquoHelicobacter pyloriinfection recruits bone marrow-derived cells that participate ingastric preneoplasia in micerdquo Gastroenterology vol 142 no 2pp 281ndash291 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

BioMed Research International 5

Shiotani et al reported that the expression of oncogenicmicroRNAs (miR-1792 and themiR-106b-93-25 clustermiR-21 miR-194 and miR-196) is significantly higher in theintestinal than nonintestinalmetaplasiaH pylori eradicationimproves microRNA deregulation but not in the intesti-nal metaplasia MicroRNA deregulation is not completelyreversible by eradication alone in long-term H pylori colo-nization [44]

Runt domain transcription factor 3 (RUNX3) is a tumorsuppressor that is silenced in cancer via hypermethylationof its promoter Previously we reported that H pylorieradication significantly increases RUNX3 expression ingastric epithelial cells [45] Lai et al reported that miR-130b expression is upregulated in gastric cancer and thisis inversely associated with Runx3 hypermethylation [46]miR-130b overexpression increases cell viability and reducescell death following the downregulation of RUNX3 proteinexpression Recently Wang et al reported that miR-301ais upregulated in gastric cancer and directly downregulatesRUNX3 expression [47]

Furthermore microR-34bc is considered a tumor sup-pressor and transcriptional target of p53 Based on a sched-uled follow-up study of endoscopic biopsy from noncancer-ous mucosa in the gastric body from 129 patients after cura-tive endoscopic resection of gastric cancer the cumulativeincidence of metachronous gastric cancer was significantlyhigher among patients with elevated miR-34bc methylationindicating that methylation of miR-34bc in the gastricmucosa may be a useful biomarker for predicting the risk ofmetachronous gastric cancer [48]

10 Cancer Stem Cell

Cancer stem cells have been defined as a unique subpop-ulation in tumors that possess the ability to initiate tumorgrowth and sustain tumor self-renewal Gastric cancer stemcells were first isolated and identified in 2009 Takaishi etal identified CD44 as a gastric cancer stem cell marker asCD44+ cells were able to form into spheroid colonies inserum-free media in vitro and gastric tumors after xenograftsin nude mice in vivo whereas CD44-negative sorted cellswere not [49]These cells have the ability for self-regenerationand resistance for chemotherapy- or radiation-induced celldeath Cancer stem cells-targeted therapy is a novel directionfor treating and preventing gastric cancer In our recent studytranslocated CagA fromH pylori to the epithelial cells couldaccumulate in CD44v9-expressing gastric cancer stem-likecells by escaping the autophagic degradation pathway dueto their characteristics of xCT-dependent ROS resistance[16]

The high expression of CD44 is positively correlated withmalignant transformation metastasis and relapse of gastriccancer [50] We previously reported that the recurrence rateof early gastric cancerwas significantly higher in theCD44v9-positive than the CD44v9-negative cohorts (hazard ratio218 95 CI 571ndash831) [42] CD44v9 expression in the tissueof primary gastric cancer represents a potential predictivemarker for recurrence

Additionally there is another hypothesis It is thoughtthat gastric cancer stem cells are derived from bone-marrow-derived mesenchymal stem cells When there is injury thebone-marrow-derived mesenchymal stem cells can mobilizefrom the bone marrow and participate in tissue repairVaron et al labeled bone-marrow-derived cells with greenfluorescent protein in mice model of infection withH pyloriAfter 1 year gastric glands that contained green fluorescentprotein-positive cells were detected in 90 of mice infectedwith H pylori Almost 25 of high-grade dysplastic lesionsincluded cells originating from the bone marrow [51] Theresults suggest that bone-marrow-derivedmesenchymal stemcells are the source of gastric cancer

11 Conclusion

As shown in this review molecular mechanisms of gastriccarcinogenesis have been extensively studied Alterationsin multiple genes and complex copy number and geneexpression profiles have been identified in gastric cancerover the two decades New strategies had been developedfor advanced gastric cancer treatment However the responserates remain in the 25ndash40 range across published trials andnovel molecularly directed approaches are needed

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

We would like to thank Drs Takanori Kanai and NaohisaYahagi for their comments to the final version of the paper

References

[1] K Fukase M Kato S Kikuchi et al ldquoEffect of eradicationof Helicobacter pylori on incidence of metachronous gastriccarcinoma after endoscopic resection of early gastric cancer anopen-label randomised controlled trialrdquo The Lancet vol 372no 9636 pp 392ndash397 2008

[2] H Suzuki T Nishizawa and T Hibi ldquoHelicobacter pylorieradication therapyrdquo Future Microbiology vol 5 no 4 pp 639ndash648 2010

[3] T Nishizawa H Suzuki I Nakagawa et al ldquoEarly Helicobacterpylori eradication restores sonic hedgehog expression in thegastric mucosa of mongolian gerbilsrdquo Digestion vol 79 no 2pp 99ndash108 2009

[4] M Ito S Takata M Tatsugami et al ldquoClinical preventionof gastric cancer by Helicobacter pylori eradication therapy asystematic reviewrdquo Journal of Gastroenterology vol 44 no 5pp 365ndash371 2009

[5] L Fuccio R M Zagari L H Eusebi L Laterza V Cennamoand L Ceroni ldquoMeta-analysis can Helicobacter pylori eradica-tion treatment reduce the risk for gastric cancerrdquo Annals ofInternal Medicine vol 151 no 7 pp 121ndash128 2009

[6] M Asaka M Kato S-I Takahashi et al ldquoGuidelines for themanagement of Helicobacter pylori infection in Japan 2009revised editionrdquo Helicobacter vol 15 no 1 pp 1ndash20 2010

6 BioMed Research International

[7] H Suzuki T Nishizawa H Tsugawa and T Hibi ldquoMolecularapproaches and modern clinical strategies for the managementof Helicobacter pylori infection in Japanrdquo Keio Journal ofMedicine vol 61 no 4 pp 109ndash119 2012

[8] M Suzuki S Miura M Suematsu et al ldquoHelicobacter pylori-associated ammonia production enhances neutrophil- depen-dent gastric mucosal cell injuryrdquo The American Journal ofPhysiology Gastrointestinal and Liver Physiology vol 263 no5 pp G719ndashG725 1992

[9] H Suzuki T Nishizawa H Tsugawa S Mogami and T HibildquoRoles of oxidative stress in stomach disordersrdquo Journal ofClinical Biochemistry and Nutrition vol 50 no 1 pp 35ndash392012

[10] T Ishimoto O Nagano T Yae et al ldquoCD44 variant regulatesredox status in cancer cells by stabilizing the xCT subunit ofsystem xcminus and thereby promotes tumor growthrdquo Cancer Cellvol 19 no 3 pp 387ndash400 2011

[11] R Chaturvedi M Asim M B Piazuelo et al ldquoActivation ofEGFR and ERBB2 by Helicobacter pylori results in survival ofgastric epithelial cells withDNAdamagerdquoGastroenterology vol146 no 7 pp 1739e14ndash1751e14 2014

[12] SNagini ldquoCarcinomaof the stomach a reviewof epidemiologypathogenesis molecular genetics and chemopreventionrdquoWorldJournal of Gastrointestinal Oncology vol 4 no 7 pp 156ndash1692012

[13] M Hatakeyama ldquoOncogenic mechanisms of the Helicobacterpylori CagA proteinrdquo Nature Reviews Cancer vol 4 no 9 pp688ndash694 2004

[14] MHatakeyama ldquoHelicobacter pyloriCagA and gastric cancer aparadigm for hit-and-run carcinogenesisrdquo Cell Host ampMicrobevol 15 pp 306ndash316 2014

[15] H Higashi R Tsutsumi A Fujita et al ldquoBiological activity ofthe Helicobacter pylori virulence factor CagA is determined byvariation in the tyrosine phosphorylation sitesrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 99 no 22 pp 14428ndash14433 2002

[16] H Tsugawa H Suzuki H Saya et al ldquoReactive oxygen species-induced autophagic degradation of Helicobacter pylori CagA isspecifically suppressed in cancer stem-like cellsrdquo Cell Host andMicrobe vol 12 no 6 pp 764ndash777 2012

[17] N Nagata J Akiyama H Marusawa et al ldquoEnhanced expres-sion of activation-induced cytidine deaminase in human gastricmucosa infected by Helicobacter pylori and its decrease follow-ing eradicationrdquo Journal of Gastroenterology vol 49 no 3 pp427ndash435 2014

[18] Y Matsumoto H Marusawa K Kinoshita et al ldquoHelicobacterpylori infection triggers aberrant expression of activation-induced cytidine deaminase in gastric epitheliumrdquo NatureMedicine vol 13 no 4 pp 470ndash476 2007

[19] T Shimizu H Marusawa Y Matsumoto et al ldquoAccumulationof somatic mutations in TP53 in gastric epithelium withHelicobacter pylori infectionrdquo Gastroenterology vol 147 no 2pp 407e3ndash417e3 2014

[20] W Yang A Raufi and S J Klempner ldquoTargeted therapy forgastric cancer molecular pathways and ongoing investigationsrdquoBiochimica et Biophysica Acta vol 1846 no 1 pp 232ndash237 2014

[21] H-CChenH-J ChenMAKhan et al ldquoGeneticmutations ofp53 and k-ras in gastric carcinomapatients fromHunanChinardquoTumor Biology vol 32 no 2 pp 367ndash373 2011

[22] T Hiyama K Haruma Y Kitadai et al ldquoK-ras mutation inHelicobacter pylori-associated chronic gastritis in patients with

and without gastric cancerrdquo International Journal of Cancer vol97 no 5 pp 562ndash566 2002

[23] Y-J Bang E Van Cutsem A Feyereislova et al ldquoTrastuzumabin combination with chemotherapy versus chemotherapy alonefor treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA) a phase 3 open-labelrandomised controlled trialrdquoThe Lancet vol 376 no 9742 pp687ndash697 2010

[24] F Lordick Y-K Kang H-C Chung et al ldquoCapecitabine andcisplatin with or without cetuximab for patients with previouslyuntreated advanced gastric cancer (EXPAND) a randomisedopen-label phase 3 trialrdquoThe Lancet Oncology vol 14 no 6 pp490ndash499 2013

[25] T Waddell I Chau D Cunningham et al ldquoEpirubicin oxali-platin and capecitabine with or without panitumumab forpatients with previously untreated advanced oesophagogastriccancer (REAL3) a randomised open-label phase 3 trialrdquo TheLancet Oncology vol 14 no 6 pp 481ndash489 2013

[26] T Satoh R H Xu H C Chung et al ldquoLapatinib pluspaclitaxel versus paclitaxel alone in the second-line treatment ofHER2-amplified advanced gastric cancer in Asian populationsTyTAN-a randomized phase III studyrdquo Journal of ClinicalOncology vol 32 pp 2039ndash2049 2014

[27] A Ohtsu J A Ajani Y-X Bai et al ldquoEverolimus for previouslytreated advanced gastric cancer results of the randomizeddouble-blind phase III GRANITE-1 studyrdquo Journal of ClinicalOncology vol 31 no 31 pp 3935ndash3943 2013

[28] H I Grabsch and P Tan ldquoGastric cancer pathology andunderlying molecular mechanismsrdquo Digestive Surgery vol 30no 2 pp 150ndash158 2013

[29] A Horii S Nakatsuru Y Miyoshi et al ldquoThe APC generesponsible for familial adenomatous polyposis is mutated inhuman gastric cancerrdquoCancer Research vol 52 no 11 pp 3231ndash3233 1992

[30] Y-GWenQWangC-Z ZhouG-QQiu Z-H Peng andH-M Tang ldquoMutation analysis of tumor suppressor gene PTEN inpatients with gastric carcinomas and its impact on PI3KAKTpathwayrdquo Oncology Reports vol 24 no 1 pp 89ndash95 2010

[31] X-T Hu and C He ldquoRecent progress in the study of methylatedtumor suppressor genes in gastric cancerrdquo Chinese Journal ofCancer vol 32 no 1 pp 31ndash41 2013

[32] H-L Wang P-Y Zhou P Liu and Y Zhang ldquoRole of p16gene promoter methylation in gastric carcinogenesis a meta-analysisrdquo Molecular Biology Reports vol 41 no 7 pp 4481ndash4492 2014

[33] A S L Cheng M S Li W Kang et al ldquoHelicobacter pyloricauses epigenetic dysregulation of FOXD3 to promote gastriccarcinogenesisrdquo Gastroenterology vol 144 no 1 pp 122e9ndash133e9 2013

[34] Y Hayashi M Tsujii J Wang et al ldquoCagA mediates epigeneticregulation to attenuate let-7 expression in Helicobacter pylori-related carcinogenesisrdquo Gut vol 62 no 11 pp 1536ndash1546 2013

[35] S Nanjo K Asada S Yamashita et al ldquoIdentification of gastriccancer riskmarkers that are informative in individuals with pastH pylori infectionrdquo Gastric Cancer vol 15 no 4 pp 382ndash3882012

[36] T Niwa T Toyoda T Tsukamoto A Mori M Tatematsu andT Ushijima ldquoPrevention of Helicobacter pylori-induced gastriccancers in gerbils by a DNA demethylating agentrdquo CancerPrevention Research vol 6 no 4 pp 263ndash270 2013

[37] E van Cutsem S de Haas Y-K Kang et al ldquoBevacizumabin combination with chemotherapy as first-line therapy in

BioMed Research International 7

advanced gastric cancer a biomarker evaluation from theAVAGAST randomized phase III trialrdquo Journal of ClinicalOncology vol 30 no 17 pp 2119ndash2127 2012

[38] L Shen J Li J Xu et al ldquoBevacizumab plus capecitabine andcisplatin in Chinese patients with inoperable locally advancedor metastatic gastric or gastroesophageal junction cancerrandomized double-blind phase III study (AVATAR study)rdquoGastric Cancer 2014

[39] C S Fuchs J Tomasek C J Yong et al ldquoRamucirumabmonotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (REGARD) an inter-national randomised multicentre placebo-controlled phase 3trialrdquoThe Lancet vol 383 no 9911 pp 31ndash39 2014

[40] J Li S Qin J Xu et al ldquoApatinib for chemotherapy-refractoryadvanced metastatic gastric cancer results from a randomizedplacebo-controlled parallel-arm phase II trialrdquo Journal ofClinical Oncology vol 31 no 26 pp 3219ndash3225 2013

[41] T Nishizawa and H Suzuki ldquoThe role of microRNA in gastricmalignancyrdquo International Journal of Molecular Sciences vol 14no 5 pp 9487ndash9496 2013

[42] K Hirata H Suzuki H Imaeda et al ldquoCD44 variant 9expression in primary early gastric cancer as a predictivemarkerfor recurrencerdquoBritish Journal of Cancer vol 109 no 2 pp 379ndash386 2013

[43] Y-Y Ma and H-Q Tao ldquoMicroribonucleic acids and gastriccancerrdquo Cancer Science vol 103 no 4 pp 620ndash625 2012

[44] A Shiotani N Uedo H Iishi et al ldquoH pylori eradication didnot improve dysregulation of specific oncogenic miRNAs inintestinal metaplastic glandsrdquo Journal of Gastroenterology vol47 no 9 pp 988ndash998 2012

[45] M Suzuki H Suzuki Y Minegishi K Ito T Nishizawaand T Hibi ldquoH pylori-eradication therapy increases RUNX3expression in the glandular epithelial cells in enlarged-foldgastritisrdquo Journal of Clinical Biochemistry and Nutrition vol 46no 3 pp 259ndash264 2010

[46] K W Lai K X Koh M Loh et al ldquoMicroRNA-130b regulatesthe tumour suppressor RUNX3 in gastric cancerrdquo EuropeanJournal of Cancer vol 46 no 8 pp 1456ndash1463 2010

[47] MWang C Li B Yu et al ldquoOverexpressedmiR-301a promotescell proliferation and invasion by targeting RUNX3 in gastriccancerrdquo Journal of Gastroenterology vol 48 no 9 pp 1023ndash10332013

[48] R Suzuki E Yamamoto M Nojima et al ldquoAberrant methy-lation of microRNA-34bc is a predictive marker of metach-ronous gastric cancer riskrdquo Journal of Gastroenterology vol 49no 7 pp 1135ndash1144 2014

[49] S Takaishi T Okumura S Tu et al ldquoIdentification of gastriccancer stem cells using the cell surface marker CD44rdquo StemCells vol 27 no 5 pp 1006ndash1020 2009

[50] Y Wakamatsu N Sakamoto H Z Oo et al ldquoExpression ofcancer stem cell markers ALDH1 CD44 and CD133 in primarytumor and lymph node metastasis of gastric cancerrdquo PathologyInternational vol 62 no 2 pp 112ndash119 2012

[51] C Varon P Dubus F Mazurier et al ldquoHelicobacter pyloriinfection recruits bone marrow-derived cells that participate ingastric preneoplasia in micerdquo Gastroenterology vol 142 no 2pp 281ndash291 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

6 BioMed Research International

[7] H Suzuki T Nishizawa H Tsugawa and T Hibi ldquoMolecularapproaches and modern clinical strategies for the managementof Helicobacter pylori infection in Japanrdquo Keio Journal ofMedicine vol 61 no 4 pp 109ndash119 2012

[8] M Suzuki S Miura M Suematsu et al ldquoHelicobacter pylori-associated ammonia production enhances neutrophil- depen-dent gastric mucosal cell injuryrdquo The American Journal ofPhysiology Gastrointestinal and Liver Physiology vol 263 no5 pp G719ndashG725 1992

[9] H Suzuki T Nishizawa H Tsugawa S Mogami and T HibildquoRoles of oxidative stress in stomach disordersrdquo Journal ofClinical Biochemistry and Nutrition vol 50 no 1 pp 35ndash392012

[10] T Ishimoto O Nagano T Yae et al ldquoCD44 variant regulatesredox status in cancer cells by stabilizing the xCT subunit ofsystem xcminus and thereby promotes tumor growthrdquo Cancer Cellvol 19 no 3 pp 387ndash400 2011

[11] R Chaturvedi M Asim M B Piazuelo et al ldquoActivation ofEGFR and ERBB2 by Helicobacter pylori results in survival ofgastric epithelial cells withDNAdamagerdquoGastroenterology vol146 no 7 pp 1739e14ndash1751e14 2014

[12] SNagini ldquoCarcinomaof the stomach a reviewof epidemiologypathogenesis molecular genetics and chemopreventionrdquoWorldJournal of Gastrointestinal Oncology vol 4 no 7 pp 156ndash1692012

[13] M Hatakeyama ldquoOncogenic mechanisms of the Helicobacterpylori CagA proteinrdquo Nature Reviews Cancer vol 4 no 9 pp688ndash694 2004

[14] MHatakeyama ldquoHelicobacter pyloriCagA and gastric cancer aparadigm for hit-and-run carcinogenesisrdquo Cell Host ampMicrobevol 15 pp 306ndash316 2014

[15] H Higashi R Tsutsumi A Fujita et al ldquoBiological activity ofthe Helicobacter pylori virulence factor CagA is determined byvariation in the tyrosine phosphorylation sitesrdquo Proceedings ofthe National Academy of Sciences of the United States of Americavol 99 no 22 pp 14428ndash14433 2002

[16] H Tsugawa H Suzuki H Saya et al ldquoReactive oxygen species-induced autophagic degradation of Helicobacter pylori CagA isspecifically suppressed in cancer stem-like cellsrdquo Cell Host andMicrobe vol 12 no 6 pp 764ndash777 2012

[17] N Nagata J Akiyama H Marusawa et al ldquoEnhanced expres-sion of activation-induced cytidine deaminase in human gastricmucosa infected by Helicobacter pylori and its decrease follow-ing eradicationrdquo Journal of Gastroenterology vol 49 no 3 pp427ndash435 2014

[18] Y Matsumoto H Marusawa K Kinoshita et al ldquoHelicobacterpylori infection triggers aberrant expression of activation-induced cytidine deaminase in gastric epitheliumrdquo NatureMedicine vol 13 no 4 pp 470ndash476 2007

[19] T Shimizu H Marusawa Y Matsumoto et al ldquoAccumulationof somatic mutations in TP53 in gastric epithelium withHelicobacter pylori infectionrdquo Gastroenterology vol 147 no 2pp 407e3ndash417e3 2014

[20] W Yang A Raufi and S J Klempner ldquoTargeted therapy forgastric cancer molecular pathways and ongoing investigationsrdquoBiochimica et Biophysica Acta vol 1846 no 1 pp 232ndash237 2014

[21] H-CChenH-J ChenMAKhan et al ldquoGeneticmutations ofp53 and k-ras in gastric carcinomapatients fromHunanChinardquoTumor Biology vol 32 no 2 pp 367ndash373 2011

[22] T Hiyama K Haruma Y Kitadai et al ldquoK-ras mutation inHelicobacter pylori-associated chronic gastritis in patients with

and without gastric cancerrdquo International Journal of Cancer vol97 no 5 pp 562ndash566 2002

[23] Y-J Bang E Van Cutsem A Feyereislova et al ldquoTrastuzumabin combination with chemotherapy versus chemotherapy alonefor treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA) a phase 3 open-labelrandomised controlled trialrdquoThe Lancet vol 376 no 9742 pp687ndash697 2010

[24] F Lordick Y-K Kang H-C Chung et al ldquoCapecitabine andcisplatin with or without cetuximab for patients with previouslyuntreated advanced gastric cancer (EXPAND) a randomisedopen-label phase 3 trialrdquoThe Lancet Oncology vol 14 no 6 pp490ndash499 2013

[25] T Waddell I Chau D Cunningham et al ldquoEpirubicin oxali-platin and capecitabine with or without panitumumab forpatients with previously untreated advanced oesophagogastriccancer (REAL3) a randomised open-label phase 3 trialrdquo TheLancet Oncology vol 14 no 6 pp 481ndash489 2013

[26] T Satoh R H Xu H C Chung et al ldquoLapatinib pluspaclitaxel versus paclitaxel alone in the second-line treatment ofHER2-amplified advanced gastric cancer in Asian populationsTyTAN-a randomized phase III studyrdquo Journal of ClinicalOncology vol 32 pp 2039ndash2049 2014

[27] A Ohtsu J A Ajani Y-X Bai et al ldquoEverolimus for previouslytreated advanced gastric cancer results of the randomizeddouble-blind phase III GRANITE-1 studyrdquo Journal of ClinicalOncology vol 31 no 31 pp 3935ndash3943 2013

[28] H I Grabsch and P Tan ldquoGastric cancer pathology andunderlying molecular mechanismsrdquo Digestive Surgery vol 30no 2 pp 150ndash158 2013

[29] A Horii S Nakatsuru Y Miyoshi et al ldquoThe APC generesponsible for familial adenomatous polyposis is mutated inhuman gastric cancerrdquoCancer Research vol 52 no 11 pp 3231ndash3233 1992

[30] Y-GWenQWangC-Z ZhouG-QQiu Z-H Peng andH-M Tang ldquoMutation analysis of tumor suppressor gene PTEN inpatients with gastric carcinomas and its impact on PI3KAKTpathwayrdquo Oncology Reports vol 24 no 1 pp 89ndash95 2010

[31] X-T Hu and C He ldquoRecent progress in the study of methylatedtumor suppressor genes in gastric cancerrdquo Chinese Journal ofCancer vol 32 no 1 pp 31ndash41 2013

[32] H-L Wang P-Y Zhou P Liu and Y Zhang ldquoRole of p16gene promoter methylation in gastric carcinogenesis a meta-analysisrdquo Molecular Biology Reports vol 41 no 7 pp 4481ndash4492 2014

[33] A S L Cheng M S Li W Kang et al ldquoHelicobacter pyloricauses epigenetic dysregulation of FOXD3 to promote gastriccarcinogenesisrdquo Gastroenterology vol 144 no 1 pp 122e9ndash133e9 2013

[34] Y Hayashi M Tsujii J Wang et al ldquoCagA mediates epigeneticregulation to attenuate let-7 expression in Helicobacter pylori-related carcinogenesisrdquo Gut vol 62 no 11 pp 1536ndash1546 2013

[35] S Nanjo K Asada S Yamashita et al ldquoIdentification of gastriccancer riskmarkers that are informative in individuals with pastH pylori infectionrdquo Gastric Cancer vol 15 no 4 pp 382ndash3882012

[36] T Niwa T Toyoda T Tsukamoto A Mori M Tatematsu andT Ushijima ldquoPrevention of Helicobacter pylori-induced gastriccancers in gerbils by a DNA demethylating agentrdquo CancerPrevention Research vol 6 no 4 pp 263ndash270 2013

[37] E van Cutsem S de Haas Y-K Kang et al ldquoBevacizumabin combination with chemotherapy as first-line therapy in

BioMed Research International 7

advanced gastric cancer a biomarker evaluation from theAVAGAST randomized phase III trialrdquo Journal of ClinicalOncology vol 30 no 17 pp 2119ndash2127 2012

[38] L Shen J Li J Xu et al ldquoBevacizumab plus capecitabine andcisplatin in Chinese patients with inoperable locally advancedor metastatic gastric or gastroesophageal junction cancerrandomized double-blind phase III study (AVATAR study)rdquoGastric Cancer 2014

[39] C S Fuchs J Tomasek C J Yong et al ldquoRamucirumabmonotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (REGARD) an inter-national randomised multicentre placebo-controlled phase 3trialrdquoThe Lancet vol 383 no 9911 pp 31ndash39 2014

[40] J Li S Qin J Xu et al ldquoApatinib for chemotherapy-refractoryadvanced metastatic gastric cancer results from a randomizedplacebo-controlled parallel-arm phase II trialrdquo Journal ofClinical Oncology vol 31 no 26 pp 3219ndash3225 2013

[41] T Nishizawa and H Suzuki ldquoThe role of microRNA in gastricmalignancyrdquo International Journal of Molecular Sciences vol 14no 5 pp 9487ndash9496 2013

[42] K Hirata H Suzuki H Imaeda et al ldquoCD44 variant 9expression in primary early gastric cancer as a predictivemarkerfor recurrencerdquoBritish Journal of Cancer vol 109 no 2 pp 379ndash386 2013

[43] Y-Y Ma and H-Q Tao ldquoMicroribonucleic acids and gastriccancerrdquo Cancer Science vol 103 no 4 pp 620ndash625 2012

[44] A Shiotani N Uedo H Iishi et al ldquoH pylori eradication didnot improve dysregulation of specific oncogenic miRNAs inintestinal metaplastic glandsrdquo Journal of Gastroenterology vol47 no 9 pp 988ndash998 2012

[45] M Suzuki H Suzuki Y Minegishi K Ito T Nishizawaand T Hibi ldquoH pylori-eradication therapy increases RUNX3expression in the glandular epithelial cells in enlarged-foldgastritisrdquo Journal of Clinical Biochemistry and Nutrition vol 46no 3 pp 259ndash264 2010

[46] K W Lai K X Koh M Loh et al ldquoMicroRNA-130b regulatesthe tumour suppressor RUNX3 in gastric cancerrdquo EuropeanJournal of Cancer vol 46 no 8 pp 1456ndash1463 2010

[47] MWang C Li B Yu et al ldquoOverexpressedmiR-301a promotescell proliferation and invasion by targeting RUNX3 in gastriccancerrdquo Journal of Gastroenterology vol 48 no 9 pp 1023ndash10332013

[48] R Suzuki E Yamamoto M Nojima et al ldquoAberrant methy-lation of microRNA-34bc is a predictive marker of metach-ronous gastric cancer riskrdquo Journal of Gastroenterology vol 49no 7 pp 1135ndash1144 2014

[49] S Takaishi T Okumura S Tu et al ldquoIdentification of gastriccancer stem cells using the cell surface marker CD44rdquo StemCells vol 27 no 5 pp 1006ndash1020 2009

[50] Y Wakamatsu N Sakamoto H Z Oo et al ldquoExpression ofcancer stem cell markers ALDH1 CD44 and CD133 in primarytumor and lymph node metastasis of gastric cancerrdquo PathologyInternational vol 62 no 2 pp 112ndash119 2012

[51] C Varon P Dubus F Mazurier et al ldquoHelicobacter pyloriinfection recruits bone marrow-derived cells that participate ingastric preneoplasia in micerdquo Gastroenterology vol 142 no 2pp 281ndash291 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

BioMed Research International 7

advanced gastric cancer a biomarker evaluation from theAVAGAST randomized phase III trialrdquo Journal of ClinicalOncology vol 30 no 17 pp 2119ndash2127 2012

[38] L Shen J Li J Xu et al ldquoBevacizumab plus capecitabine andcisplatin in Chinese patients with inoperable locally advancedor metastatic gastric or gastroesophageal junction cancerrandomized double-blind phase III study (AVATAR study)rdquoGastric Cancer 2014

[39] C S Fuchs J Tomasek C J Yong et al ldquoRamucirumabmonotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (REGARD) an inter-national randomised multicentre placebo-controlled phase 3trialrdquoThe Lancet vol 383 no 9911 pp 31ndash39 2014

[40] J Li S Qin J Xu et al ldquoApatinib for chemotherapy-refractoryadvanced metastatic gastric cancer results from a randomizedplacebo-controlled parallel-arm phase II trialrdquo Journal ofClinical Oncology vol 31 no 26 pp 3219ndash3225 2013

[41] T Nishizawa and H Suzuki ldquoThe role of microRNA in gastricmalignancyrdquo International Journal of Molecular Sciences vol 14no 5 pp 9487ndash9496 2013

[42] K Hirata H Suzuki H Imaeda et al ldquoCD44 variant 9expression in primary early gastric cancer as a predictivemarkerfor recurrencerdquoBritish Journal of Cancer vol 109 no 2 pp 379ndash386 2013

[43] Y-Y Ma and H-Q Tao ldquoMicroribonucleic acids and gastriccancerrdquo Cancer Science vol 103 no 4 pp 620ndash625 2012

[44] A Shiotani N Uedo H Iishi et al ldquoH pylori eradication didnot improve dysregulation of specific oncogenic miRNAs inintestinal metaplastic glandsrdquo Journal of Gastroenterology vol47 no 9 pp 988ndash998 2012

[45] M Suzuki H Suzuki Y Minegishi K Ito T Nishizawaand T Hibi ldquoH pylori-eradication therapy increases RUNX3expression in the glandular epithelial cells in enlarged-foldgastritisrdquo Journal of Clinical Biochemistry and Nutrition vol 46no 3 pp 259ndash264 2010

[46] K W Lai K X Koh M Loh et al ldquoMicroRNA-130b regulatesthe tumour suppressor RUNX3 in gastric cancerrdquo EuropeanJournal of Cancer vol 46 no 8 pp 1456ndash1463 2010

[47] MWang C Li B Yu et al ldquoOverexpressedmiR-301a promotescell proliferation and invasion by targeting RUNX3 in gastriccancerrdquo Journal of Gastroenterology vol 48 no 9 pp 1023ndash10332013

[48] R Suzuki E Yamamoto M Nojima et al ldquoAberrant methy-lation of microRNA-34bc is a predictive marker of metach-ronous gastric cancer riskrdquo Journal of Gastroenterology vol 49no 7 pp 1135ndash1144 2014

[49] S Takaishi T Okumura S Tu et al ldquoIdentification of gastriccancer stem cells using the cell surface marker CD44rdquo StemCells vol 27 no 5 pp 1006ndash1020 2009

[50] Y Wakamatsu N Sakamoto H Z Oo et al ldquoExpression ofcancer stem cell markers ALDH1 CD44 and CD133 in primarytumor and lymph node metastasis of gastric cancerrdquo PathologyInternational vol 62 no 2 pp 112ndash119 2012

[51] C Varon P Dubus F Mazurier et al ldquoHelicobacter pyloriinfection recruits bone marrow-derived cells that participate ingastric preneoplasia in micerdquo Gastroenterology vol 142 no 2pp 281ndash291 2012

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology