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Original Research Article
Identification of pivotal cellular factors involved in HPV‐induced dysplastic and neoplastic cervical pathologies†
Stefano Mattarocci1$, Claudia Abbruzzese2$, Anna M. Mileo2, Mariantonia Carosi3, Edoardo Pescarmona3, Carmen Vico2, Antonio Federico2, Enrico Vizza4, Giacomo Corrado4, Ivan Arisi5
Armando Felsani6 and Marco G. Paggi2* 1 Department of Molecular Biology, University of Geneva, 30, quai Ernest‐Ansermet, 1211 Geneva, Switzerland.
2 Department. of Development of Therapeutic Programs, Regina Elena National Cancer Institute, Via E. Chianesi, 53, 00144 Rome, Italy.
3 Department of Pathology, Regina Elena National Cancer Institute, Via E. Chianesi, 53, 00144 Rome, Italy
4 Department of Gynecology, Regina Elena National Cancer Institute, Via E. Chianesi, 53, 00144 Rome, Italy
5 Genomics Facility, European Brain Research Institute (EBRI) “Rita Levi‐Montalcini”, Via Fosso di Fiorano, 64, 00143 Rome, Italy
6 CNR, Istituto di Neurobiologia e Medicina Molecolare, Via Fosso di Fiorano, 64, 00143 Rome, Italy
$ These authors contributed equally to this work Running head: Genes involved in cervical dysplasia and cancer Keywords: HPV, Cervical Dysplasia, Cervical Cancer, Viral Oncogenesis Contract grant sponsors: This work was supported by grants from Associazione Italiana Ricerca sul Cancro (AIRC) (www.airc.it) and Ministero della Salute (www.ministerosalute.it) grants to M.G.P., from Ministero dell’Università dell’Istruzione e della Ricerca (www.miur.it) (FIRB No. RBAP10L8TY) and Fondazione Roma to I.A. and grant CNR “Medicina Personalizzata” to A.F. * Corresponding author: Marco G. Paggi, MD, PhD Regina Elena National Cancer Institute, Via Elio Chianesi, 53, 00144 Rome, Italy Tel.: +39‐06‐5266.2550 ‐ Fax: +39‐06‐8928.2762 Email: [email protected] †This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: [10.1002/jcp.24465] Additional Supporting Information may be found in the online version of this article.
Received 18 July 2013; Revised 20 August 2013; Accepted 29 August 2013 Journal of Cellular Physiology © 2013 Wiley Periodicals, Inc.
DOI 10 .1002 / j cp .24465
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Abs t rac t Cervical carcinoma represents the paradigm of virus‐induced cancers, where virtually all
cervical cancers come from previous “high‐risk” HPV infection. The persistent expression of the
HPV viral oncoproteins E6 and E7 is responsible for the reprogramming of fundamental cellular
functions in the host cell, thus generating a noticeable, yet only partially explored, imbalance in
protein molecular networks and cell signaling pathways. Eighty‐eight cellular factors, identified as
HPV direct or surrogate targets, were chosen and monitored in a retrospective analysis for their
mRNA expression in HPV‐induced cervical lesions, from dysplasia to cancer. Real‐time quantitative
PCR (qPCR) was performed by using formalin‐fixed, paraffin embedded archival samples. Gene
expression analysis identified 40 genes significantly modulated in LSIL, HSIL and squamous cervical
carcinoma. Interestingly, among these, the expression level of a panel of four genes, TOP2A,
CTNNB1, PFKM and GSN, was able to distinguish between normal tissues and cervical carcinomas.
Immunohistochemistry was also done to assess protein expression of two genes among those up‐
regulated during the transition between dysplasia and carcinoma, namely E2F1 and CDC25A, and
their correlation with clinical parameters. Besides the possibility of significantly enhancing the use
of some of these factors in diagnostic or prognostic procedures, these data clearly outline specific
pathways, and thus key biological processes, altered in cervical dysplasia and carcinoma. Deeper
insight on how these molecular mechanisms work may help widen the spectrum of novel
innovative approaches to these virus‐induced cell pathologies.
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I n t roduc t i on
Infection from different pathogens is recognized as a major cause of cancer (zur Hausen,
2009;de Martel C. et al, 2012). Among these infectious agents, the body of knowledge concerning
the role of “high‐risk” Human Papillomavirus (HPV) strains, mainly HPV 16 and HPV 18, in cervical
cancer appears large and consistent. Over the last few years, cervical cancer incidence and death
rates are falling, mainly due to the access to reliable screening procedures which facilitate early
diagnosis and treatment (Siegel et al, 2013). While HPV vaccines represent a promising preventive
approach towards HPV infection and related neoplastic diseases, their therapeutic effectiveness is
yet to be proven. Despite ongoing massive anti‐HPV vaccination campaigns, a significant number
of cancers are still expected to occur mainly in developing countries due to cultural and socio‐
economic reasons and to the potential selection of high‐risk HPV strains not neutralized by the
vaccines.
HPV‐induced tumors usually arise several years after viral infection, displaying the
integration of the viral genome into cancer cell chromosomes, which allows the stabilized
expression of the E6 and E7 oncogenes and of the respective protein products, the E6 and E7
oncoproteins. These are the major effectors of HPV‐driven cell transformation and appear also
central for cancer cell clones maintenance and proliferation by acting via several molecular
mechanisms able to weaken normal cell cycle control and modulate the cellular apoptotic
response (Fehrmann and Laimins, 2003;Munger et al, 2004;Whiteside et al, 2008;McLaughlin‐
Drubin and Munger, 2009;Bellacchio and Paggi, 2013). Interestingly, E6 and E7 from high‐risk HPV
strains are void of any enzymatic activity, but display the peculiarity to generate specific protein‐
protein interactions through which they are able to reprogram fundamental cellular functions.
Nowadays, the most investigated cellular targets of E6 and E7 are the p53 and the Retinoblastoma
(RB) family proteins, respectively (Helt and Galloway, 2003;Felsani et al, 2006). In several cases,
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the endogenous factors targeted by the small DNA virus oncoproteins undergo dramatic changes
also in their cellular amount, due to direct effects on the protein or to transcriptional interference
(Munger et al, 2001;Helt and Galloway, 2003;Felsani et al, 2006;Mileo et al, 2013).
In HPV‐induced pathologies of the uterine cervix, the discovery of sensitive and specific
biomarkers differentially expressed in non‐progressive and progressive diseases might efficiently
integrate the current procedures for risk assessment and inform therapeutic decisions.
The purpose of our study was to identify pivotal factors involved in dysplastic and
neoplastic cervical pathologies, in order to gain information on the molecular processes
implicated in these HPV‐induced processes. Therefore, we selected a series of cellular factors
whose amount appears modulated in HPV‐related cervical pathologies plus others chosen through
experimental data generated in our laboratory. We then performed an extensive quantitative PCR
(qPCR) analysis by monitoring a supervised set of 88 cellular genes possibly involved in cervical
dysplastic and neoplastic diseases. Our samples consisted of a set of 127 formalin‐fixed paraffin‐
embedded (FFPE) archival cervical samples, including control cases, Low‐grade Squamous
Intraepithelial Lesions (LSIL), High‐grade Squamous Intraepithelial Lesions (HSIL) and carcinomas.
The expression of a subset of genes was found significantly different in the various categories of
cervical samples, thus some of these genes have been selected as potential indicators for
transition from dysplasia to cancer. For two of these genes, specifically E2F1 and CDC25A, analysis
of their protein product was evaluated via immunohistochemistry (IHC) in squamous cervical
carcinoma samples.
Our results can significantly promote the use of some of these factors in
diagnostic/prognostic procedures by identifying a panel of genes/proteins whose expression can
be correlated with known clinical parameters. It is crucial to direct new investigative efforts to
improve our knowledge and understanding on the molecular mechanisms behind HPV
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infection/transformation in order to widen the spectrum of novel and innovative approaches
against virus‐induced pathologies.
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Mate r i a l s and Methods
Pat i en t s
Tissues from 127 cervical surgical specimens [Control (normal cervical epithelium from
patients who underwent hysterectomy for reasons other than cancer) (22 cases), LSIL (35 cases),
HSIL (27 cases), Cervical Cancer (43 cases)] were evaluated. All the patients were diagnosed and
treated at the Regina Elena National Cancer Institute, Rome, Italy. Patients underwent
international standard therapeutic protocols. Clinical data (patient diagnosis and staging) were
obtained from the Regina Elena National Cancer Institute databases. Samples were collected
according to the current institutional ethical guidelines.
RNA ex t rac t i on and quant i ta t i ve gene exp re s s i on ana l y s i s i n arch i va l samp le s
Total RNA extraction from formalin‐fixed, paraffin‐embedded (FFPE) cervical specimens
was done as described (Abbruzzese et al, 2012). Total RNA was checked for quality and quantified
using the 2100 bioanalizer (Agilent, Santa Clara, CA). RNA samples, even with a low RNA integrity
number (RIN), were retrotranscribed using the High Capacity cDNA Reverse Transcription Kit
(Applied Biosystems, Branchburg, NJ). Each sample was then analyzed by qPCR using custom‐
made microfluidic cards (Applied Biosystems) containing sequence specific primer pairs for 88
genes to be examined and for 6 endogenous control genes (Table S1, Supplementary Material).
The cards were processed as indicated by the manufacturer using the 7900HT thermal cycler
apparatus equipped with the SDS software version 2.3 (Applied Biosystems) for data collection.
Hi s to log i ca l examina t i on and IHC
The histological diagnosis was re‐evaluated in 2‐μm FFPE sections after routine
laboratory haematoxylin/eosin staining.
IHC analysis was performed as described (Mattarocci et al, 2009) after an antigen
retrieval step, treating slides in microwave oven at 800 W for 15 min x 2 in 300 ml of 10 mM
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citrate buffer, pH 6.0.Immunostaining was carried out by using a primary monoclonal antibody for
Cdc25a (sc‐56264, Santa Cruz Biotechnology, Inc. Santa Cruz, CA), applied overnight (ON) at room
temperature (RT) at a 1:50 dilution. E2F1 was detected via a mouse monoclonal antibody (sc‐251,
Santa Cruz Biotechnology) applied ON at RT at a 1:20 dilution. For both antibodies, optimal
working dilution was defined on the basis of titration experiments. The secondary antibody
solution and streptavidin‐biotin, both from the AFN600‐IFU kit (ScyTek, Logan, UT), were applied
according to the manufacturer’s instructions. Finally, 3‐amino‐9‐ethylcarbazide (AEC substrate kit,
ScyTek, Logan, UT) was used as the final chromogen. Mayer’s haematoxylin was used for nuclear
counterstaining. Negative controls for each tissue section were prepared by omitting the primary
antibody.
To increase the number of samples to be evaluated, 208‐sample Tissue Micro Arrays
(TMA) of cervical carcinoma cases (US Biomax CR2088, Rockville, MD), containing 181 squamous
cervical carcinoma samples with I‐III grading, 9 cervical adenocarcinoma samples (not evaluated)
plus 16 normal cervix samples as negative controls, were stained for CDC25A and E2F1 expression
following the procedures described above.
The total number of evaluable squamous cervical carcinoma samples was 219.
Sco r i ng and quant i f i ca t i on o f gene exp re s s i on and immunoreac t i v i t y
Gene expression. qPCR reaction data were analyzed using the HTqPCR Bioconductor package
software (version 1.4.0) for the R statistical computing environment, version 2.12.1 (Dvinge and
Bertone, 2009). Ct values were normalized by the deltaCt method on the average of the
endogenous controls. The normalization stability score of these control RNAs was confirmed by
the GeNorm software. Data not acquired (N/A) were assigned with a default Ct value of 40.
Differential expression analysis was conducted using the functions from the R limma package
(Smyth et al, 2005), after having removed the Ct values corresponding to the endogenous controls
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and those with an Inter Quartile Range ≤1.5. P‐values were corrected for multiple testing
following Benjamini and Hochberg (Benjamini and Hochberg, 1995).
Immunoreactivity. Three examiners (MC, EP and MGP) independently evaluated the staining
pattern of Cdc25A and E2F1 in the same cervical carcinoma case series employed for mRNA
expression (42 cases) plus in an independent set of squamous cervical carcinomas on TMA slides
(181 cases). The final score derived from the independent analysis of the examiners, with
subsequent discussion for the cases in which divergent diagnoses were given. According to the
amount of specific staining, cases were classified in tertiles as follows: a) negative/low; b)
medium; c) high.
Cervical cancer samples staining positive for E2F1 displayed an immunoreactivity
characterized by a distinct nuclear staining with or without diffuse cytoplasmic staining. IHC
results for E2F1 were expressed as a percentage of the positive number of nuclear or cytoplasmic
cells separately, counted in 10 microscope cellular fields (x40). Tumors were defined positive for
E2F1 when 20% or more tumor cells showed unequivocal nuclear or cytoplasmic staining. Cases
with faint, uncertain cytoplasmic and/or nuclear staining were regarded as negative. In normal
cervical epithelium, nuclear staining appeared confined to the basal and parabasal layers.
CDC25A displayed a diffuse or granular cytoplasmic staining highly specific for carcinoma
cells. IHC results were expressed as a percentage of the positive cells, counted in 10 microscope
cellular fields (40x). Tumors were defined positive for CDC25A when 20% or more tumor cells
showed unequivocal staining. Cases with faint, uncertain staining were regarded as negative. In
normal cervical epithelium, nuclear staining was limited to the intermediate and superficial layers.
S ta t i s t i ca l ana l y s i s
To analyze differential expression of ΔCt levels in single pairwise comparisons (for
example Control vs. HSIL or Control vs. Carcinoma), the non‐parametric Mann‐Whitney U‐test was
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applied to evaluate statistical significance. All categorical variables, such as tumor stage or
International Federation of Gynecology and Obstetrics (Fédération Internationale de Gynécologie
et d'Obstétrique, FIGO) stage, were tested for statistical significance by using the Fisher’s exact
test applied to contingency tables, where expression levels, for both mRNA and protein, were
divided into three groups.
For all statistical tests, a two‐tailed P‐value < 0.05 was considered as statistically
significant.
Hierarchical clustering and Principal Component Analysis (PCA) of samples were
computed by the Multi Experiment Viewer ver. 4.6 (Saeed et al, 2006)
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Resu l t s
Choice of the genes to be assayed and of the cervical samples to be analyzed
A number of genes were chosen after a thorough survey of the published literature was
carried out. We sought for those whose mRNA and/or protein expressions that significantly
correlated with histopathological score and other clinical parameters in cervical dysplasia and
cancer. Other genes were chosen according to data derived from our in vitro studies on protein‐
protein interactions involving HPV‐16 oncoproteins and host cell factors (Mileo et al,
2006;Severino et al, 2007;Mileo et al, 2009;Mileo et al, 2013) or preliminary qPCR data in HPV‐16
E7‐expressing HaCaT immortalized human keratinocytes (data not shown). The final output
consisted of a list containing 88 genes, plus 6 housekeeping genes chosen for normalization,
whose amount was thus determined in a supervised analysis. The complete list of assayed genes,
respective protein name and references or data employed for their selection, is displayed in Table
S1 (Supplementary Material). mRNA expression for the supervised set of these 88 genes has been
thus determined in FFPE archival human specimens for a total of 127 individuals subdivided into
four cohorts by the pathologists, i.e. Control (22 cases), LSIL (35 cases), HSIL (27 cases), Cervical
Cancer (43 cases).
Gene expression Analysis (qPCR)
Raw data on the expression of 88 genes in all the analyzed samples are reported in Table
S2 (Supplementary Material). Results are shown in Figure 1 and expressed as log2 Fold Change
(FC). Assuming an arbitrary cutoff value of 1.75 Log2FC, the expression of 40 genes appeared
significantly modulated in LSIL, HSIL and cervical carcinoma, when compared with controls
(samples of normal cervical tissue). Genes were categorized as follows:
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• Up‐regulated at all stages, from Control (baseline) to LSIL, HSIL and Carcinoma: PAK6 and
MKI67. Up‐regulation of these genes was linked to a pathological state of the cervix uteri
(dysplasia or carcinoma).
• Down‐regulated at all stages, from Control (baseline) to LSIL, HSIL and Carcinoma: MYC, SIVA1,
BCL2, SNAI1, PTGS2 and FOS. Down‐regulation of these genes was linked to a pathological
state of the cervix uteri (dysplasia or carcinoma). Among these, FOS, SNAI1 and BCL2 displayed
the most evident down‐regulation.
• Progressively up‐regulated, from LSIL to HSIL and Carcinoma: E2F1, CCNE2, FOXM1, TP73,
CDC25A, BIRC 5 and TOP2A. Their expression increased significantly in dysplastic lesions and
even more in carcinomas. Among these genes, it is worth noting the consistent increase in
expression between HSIL and carcinoma found in BIRC5, CDC25A and E2F1.
• Progressively down‐regulated, from LSIL to HSIL and Carcinoma: RAD52, CAT, PKM2, IGFBP5,
MAPK3, EDNA, CAV1, GSN, ABCB1, PFKM, PTGES, VIM, CTNNB1, APC, TOP2B and LMNA. Their
expression decreased significantly in dysplastic lesions and even more in carcinomas. Among
these genes, it is worthy to note the consistent drop in expression between HSIL and
carcinoma found in IGFBP5, EDNRA and CAV1.
• Up‐regulated in HSIL and Carcinoma only: CCNE1, MMP8 and CCNB1. These genes are up‐
modulated solely in high‐grade dysplasias and carcinomas.
• Up‐regulated in LSIL (or HSIL), but down‐regulated in Carcinoma: EDN3, CST6, BCL2L1, KLK5,
KRT10 and CDH1. Their expression was lower in carcinomas than in dysplastic lesions, even if
often higher than in controls. Among these genes, it is important to consider the consistent
drop in expression observed in EDN3, KRT10 and KLK5.
A further analysis outlined a set of 4 genes (TOP2A, CTNNB1, PFKM and GSN) whose
expression, when dysplastic samples (LSIL and HSIL) were grouped (dysplasia), appeared strongly
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correlated with the overall patient status or diagnosis. These genes were selected as a highly
differentially expressed small subset by Mann‐Whitney U‐test (10‐11 < P < 10‐5) between sample
groups in all possible pairwise comparisons (Control vs. Dysplasia, Control vs. Carcinoma,
Carcinoma vs. Dysplasia). In this analysis, we considered three group samples: Control cases,
Dysplasia and Cervical Carcinoma. In Figure 2 A, Principal Component Analysis (PCA) of samples,
based on the expression values of TOP2A, CTNNB1, PFKM and GSN, showed a clear segregation
between normal tissues and cervical carcinomas, while dysplastic samples gave scattered values.
Figure 2 B shows hierarchical clustering and heat map representing the level of expression of
TOP2A, CTNNB1, PFKM and GSN across the samples analyzed. TOP2A expression levels appeared
to be clearly on the rise along with the severity of the disease, while the opposite occurred for
GSN, CTNNB1 and PFKM. Also in this case, the same 4‐gene set strongly discriminated between
normal and cancer samples, while dysplastic samples (LSIL plus HSIL) once again gave
heterogeneous results. Data are expressed as log2 Fold Change (FC) in comparison with controls
(normal cervical epithelium). Interestingly, the analysis of the data obtained from our cohort of
squamous cervical cancer patients outlined a significant correlation between low levels of
CTNNB1 mRNA expression and the presence of lymph node dissemination (Fisher’s exact test P =
0.005).
Protein expression analysis (IHC)
We focused our attention on the genes that, among the 40 genes differentially regulated,
showed a significantly increased expression between the dysplastic (LSIL + HSIL) and the
cancerous status, with the aim to perform a determination of the amount of protein products in
cancer samples by means of IHC. This choice appeared justified by the fact that the transition
between dysplasia and cancer is conceptually and clinically central, allowing to generate
potentially new information about viral carcinogenesis processes and patient diagnosis and
prognosis as well. Another key point, in order to facilitate a swift transition from research to clinic,
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was the choice of genes which appeared up‐regulated during the transition between dysplasia
and cancer. In fact, when IHC is used for determination, up‐regulation toward controls is easier
and safer to asses than down‐regulation. On these bases, the genes significantly up‐regulated
during the transition between dysplasia and carcinoma were: TOP2A, FOXM1, BIRC5, CCNE2,
CDC25A, TP73 and E2F1. Among those, we chose to assay for protein expression E2F1 and
CDC25A, two genes whose mRNA expression was significantly increased in squamous cervical
carcinomas and for which IHC data are not yet available in the literature. We examined the
expression of these two gene products in 42 cases of cervical carcinoma belonging to the samples
from which mRNA was extracted and analyzed. In addition, the samples contained in a tissue
microarray consisting in 181 cases of squamous cervical carcinoma were included, for a total of
223 carcinomas evaluated.
Positive staining for E2F1 significantly correlated with histopathological grade (Fisher’s
exact test P = 0.031), being lower in high‐grade carcinomas. No significant differences were found
when considering tumor stage (T), lymph node stage (N0 or N1) or tumor stage according to FIGO
classification (Stage I to IV). Analyzing the same parameters, positive staining for CDC25A reached
statistical significance only for lymph node stage (Fisher’s exact test P = 0.03), where N1 samples
showed higher protein content than the N0 ones (Table 1).
Examples of IHC staining for E2F1 and CDC25A in normal and cervical squamous
carcinomas are shown in Figure 3.
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Di s cus s i on
This study aimed at identifying the key factors involved in cervical dysplasia and
carcinoma in order to recognize the molecular processes implicated in these HPV‐induced
pathologies and to use the expression of specific cellular factors to more accurately address
important clinical issues.
The results reported herein allow identify a cluster of genes and gene products whose
expression is modulated during the transition from normal epithelium to dysplasia and cancer in
HPV‐generated cervical pathologies. Most of our findings are evidently consistent with the
literature data we used to build up the dataset of genes analyzed in our samples (see Table S1
Supplementary Data). The results found on other genes are strongly in accordance with the
findings reported in our previous studies (Severino et al, 2007;Mileo et al, 2013). Finally, out of
the 88 assayed genes, a cluster of four genes (Figure 2), when evaluated concomitantly, appear
capable to discriminate between normal and cancer cervical tissues: TOP2A, GSN, PFKM and
CTNNB1.
TOP2A mRNA expression was significantly higher in cervical carcinoma samples, in
accordance with protein expression as evaluated by IHC (Branca et al, 2008;Guo et al, 2011;Brown
et al, 2012).
GSN mRNA expression was significantly lower in cervical carcinoma samples. Our previous
study shows a reduced gelsolin cleavage by caspase‐3 in the presence of the HPV‐16 E7
oncoprotein (Mileo et al, 2013), which is in agreement with a decreased GSN mRNA synthesis in
cervical carcinomas.
PFKM mRNA expression was significantly lower in cervical carcinoma samples.
Phosphofructokinase M is a master regulator enzyme in the glycolytic process. While there are
several studies describing the effect of the interplay between HPV infection and pyruvate kinase
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M2 (PKM2) in increasing tumor glycolysis and enhancing the Warburg effect (Zwerschke et al,
1999;Mazurek et al, 2001;Tamada et al, 2012), to our knowledge, this is the first report in which
mRNA expression of PFKM, another key glycolytic regulator enzyme, appears modulated in HPV‐
expressing cervical pathologies.
CTNNB1 mRNA expression was significantly lower in cervical carcinoma samples. Data in
literature outline an inverse correlation between IHC‐determined beta‐catenin expression and
tissue differentiation, as well as low expression in cervical carcinoma cases with lymph node
dissemination (Cheng et al, 2012). The data herein presented are definitely consistent with these
results.
In spite of the high statistical significance of the differences in mRNA expression in this
panel of four selected genes (TOP2A, GSN, PFKM and CTNNB1), even pooling the two dysplastic
forms LSIL and HSIL was impossible to stratify the dysplastic cases, while cervical carcinomas were
found to be efficiently segregated from normal samples (Figure 2, panels A and B). The reason
why the intermediate, dysplastic state did not segregate successfully could also be explained by
the intrinsic variability found in these FFPE specimens due to their occasionally small size and
consequent possible contamination with unpredictable amounts of adjacent peri‐lesional tissue.
On the other hand, the significant variation of E2F1 determination via IHC according to
histopathological grade, being lower in high‐grade samples, is not surprising. E2F1 is the most
investigated member of the E2F family of transcription factors that actively promote the cell
entrance into the S phase. It binds to the “pocket” region of the Retinoblastoma oncosuppressor
protein, and of its related suppressor factors p107 and pRb2/p130, to be functionally inactivated
and thus unable to stimulate the cell to enter the S phase (Ewen, 1994;Weinberg, 1995;Paggi et al,
1996;Mulligan and Jacks, 1998;Paggi and Giordano, 2001). In the presence of HPV‐16 E7, E2F1 is
displaced from the Retinoblastoma protein, thus being able to exert its trans‐activating activity
16
(Chellappan et al, 1992;Morris et al, 1993;Bellacchio and Paggi, 2013). However, at the same time,
it becomes substrate of the specific proteases devoted to its turnover (Hateboer et al, 1996).
In our cohort of patients, strong IHC staining for CDC25A appeared significantly
correlated with the evidence of lymph‐node dissemination in the patient. Indeed, the CDC25A
tyrosine phosphatase is a key factor in cell cycle progression and its up‐regulation is associated
with carcinogenesis. In particular, the E7 oncoprotein from HPV‐16 is able to increase CDC25A
protein levels (Nguyen et al, 2002;Gao et al, 2009).
Now, it is important to consider that the majority of these assays detect the expression of
surrogate markers of aberrations in cell proliferation genes and that these tests cannot be swiftly
employed in a clinical setting, even after a stronger statistical validation, due to the intrinsic
complexity of the non‐routine procedures utilized. Nevertheless, these results outline genes and
gene products whose expression, appearing critical in discriminating between normal and cancer
cervical tissues, can be of great value in recognizing key HPV‐induced molecular derangements
that are hallmarks of a transformed phenotype.
In the near future, we plan to increase the number of specimens to be assayed and to
perform phosphoproteomic analysis by Reverse‐Phase Protein Microarrays (RPPM) in order to
explore the activation status of several signal transduction components in fresh, surgically
obtained cervical cancer samples. Activated signaling profiles will highlight potentially relevant
molecular biomarkers, thus generating novel classification ranks and identifying druggable targets
as well.
Indeed, grasping further knowledge of the molecular mechanisms employed by HPV in
inducing and maintaining the cancerous state will be vital in understanding these processes and
toward selecting effective therapies in defeating the HPV oncogenic machinery.
17
Acknowledgment s
The authors thank Daniela Panichi for the preparation of the FFPE archival specimens
Manuela Natoli for her help in qPCR mRNA determinations and Tania Merlino for English language
editing.
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Legends to Figures Figure 1 Supervised gene expression in LSIL, HSIL and squamous cervical carcinomas from
FFPE samples. Genes significantly modulated in Cervical Lesions: comparison with
Controls. mRNA analysis was performed in four cohorts for a total of 127 patients, i.e.
Control (22 cases), LSIL (35 cases), HSIL (27 cases), Cervical Cancer (43 cases) and is
expressed as log2 Fold Change (FC) in comparison with control (normal cervical
epithelium) (Red color scale = up‐regulation toward control; Green color scale =
down‐regulation toward control). For each gene listed, a statistical significance of P <
0.05 was achieved at least in one pathological class.
Figure 2 mRNA expression of a set of 4 genes (TOP2A, CTNNB1, PFKM and GSN) is strongly
correlated with the overall patient status or diagnosis. A. Principal Component
Analysis (PCA) of expression values of patient samples. The dataset used for clustering
is composed of normalized ΔCt expression values of genes, TOP2A, CTNNB1, PFKM
and GSN for all the samples. The color code shows how the samples segregate in the
plot, particularly along the PCA1 axis, according to diagnostic category: Control,
Dysplasia, Carcinoma. The color code is the same as in the heat map plot. B.
Hierarchical clustering and heat map of expression values of patient samples, using
Euclidean distance metric and average linkage. The dataset used for clustering is
composed of expression values of genes TOP2A, CTNNB1, PFKM and GSN for all the
samples. Values are mean centered normalized ΔCt, where for each gene the mean is
calculated across all the samples. On the bottom of the diagram, a color code shows
how the samples segregated in the cluster, according to diagnostic category: Control,
Dysplasia, and Carcinoma. In both panels, genes were selected given their extremely
different expression values in the three groups, as shown by the p‐value <10‐6 in all
pairwise non‐parametric tests (Mann‐Whitney U‐test) between the groups (Control
vs. Dysplasia, Control vs. Carcinoma, Dysplasia vs. Carcinoma). The color code, green
for Control, ochre for Dysplasia and purple for Carcinoma, is the same in both panels.
Figure 3 Immunohistochemical staining for E2F1 and CDC25A in cervical squamocellular
carcinoma and in normal cervical tissue. Representative samples of squamous
cervical carcinoma and normal cervical tissue which appear positive for E2F1 and
CDC25A staining in IHC. E2F1 staining is essentially nuclear, with or without
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cytoplasmic staining. CDC25A staining appears as a diffuse or granular cytoplasmic
staining, highly specific for carcinoma cells. Original magnification = x20.