GENETIC ANALYSIS OF THE C677T AND A1298C MTHFR POLYMORPHISMS IN A COHORT OF

ROMANIAN PATIENTS WITH SPORADIC COLORECTAL CANCER

15

C e r c e t a r ie x p e r i m e n ta le &

m edico-chirurgicale

)

Cercetãri Experimentale & Medico-Chirurgicale

Anul XIVl · Nr.1/2007 · Pag. 15-23

Abstract:Background: One of the mutated genes associated with a lower level of 5- MTHF necessary forDNA methylation and possibly implicated in the carcinogenesis of sporadic colorectal cancer(CRC) is the gene encoding the methylenetetrahydrofolate reductase enzyme (MTHFR).Objectives: to investigate the frequency of the C667T and A1298C MTHFR variants in patientswith sporadic CRC and controls; to establish the relative risk for sporadic CRC in association withthese two polymorphisms. Patients and methods: Genotyping of C677T and A1298C MTHFR polymorphisms using PCR-RFLP methods was done in 69 patients diagnosed with CRC and referred from the Surgical ClinicIII Cluj. Sixty seven individuals without any signs of malignancy formed the control group. Results: The CT677 and TT677 genotypes were greater in patients with sporadic CRC comparedto controls (34.78% vs. 25.37%, OR 1.57; 95% CI [0.74-3.28], p=0.23 and 8.69% vs. 4.47%, OR2.13; 95% CI [0.51-8.91], p=0.47, respectively). The 1298AC and CC1298 genotypes wereassociated with an OR of 1.63 (49.27% vs. 37.31%, 95% CI [0.82-3.23], p= 0.15) and 3.00 (4.34% vs. 1.49%, 95% CI [0.3-29.58], p=0.6) for sporadic CRC. Patients positive for C677T and A1298Cpolymorphisms have a higher frequency of colon cancer in the left side than in the right side(18.84% vs. 4.34%, OR 5.11, 95%CI [1.38-18.83], p< 0.01, and 23.18% vs. 10.14%, OR 2.67,95%CI [1.02-6.98], p=0.03, respectively). Moreover, patients positive for C677T and A1298Cpolymorphisms have a higher frequency of colon cancer than rectal cancer (34.78% vs. 18.84%,OR 2.3, 95%CI [1.05-5.01], p= 0.03, and 28.98% vs. 15.94%, OR 2.15, 95%CI [0.94-4.92], p=0.06, respectively). Conclusions: Our study confirms the relationship between MTHFR genotypes and sporadiccolorectal cancer. High risk individuals could benefit from effective prevention and treatmentwith 5- FU strategies in order to reduce the mortality of sporadic colorectal cancer.

Key Words:sporadic colorectal cancer, C677T, A1298C, PCR- RFLP

REZUMAT: Una dintre genele mutante asociate cu concentraþie scãzutã a 5- MTHF necesarpentru metilarea ADN ºi posibil implicatã în procesul de carcinogenezã în cancerul colorectal(CCR) sporadic este gena care codificã metilentetrahidrofolat reductaza (MTHFR). Obiective: de a investiga frecvenþa variantelor C677T ºi A1298C din gena MTHFR la pacienþii cuCCR sporadic ºi în lotul de control; de a stabili riscul relativ de a dezvolta CCR sporadic în asociere cu aceste douã polimorfisme. Material ºi metode: Genotiparea pentru C677T ºi A1298C utilizând metoda PCR- RFLP s-a fãcutîntr-un lot de 69 pacienþi diagnosticaþi cu CCR sporadic în Clinica Chirurgie III, Cluj. ªaizeci ºiºapte subiecþi fãrã semne de malignitate au format grupul de control.Rezultate: GenotipurileCT677 ºi TT677 au avut o frecvenþã mai mare în grupul de pacienþi cu CCR sporadic comparativcu lotul de control (34.78% vs. 25.37%, OR 1.57; 95% CI[0.74-3.28], p=0.23 ºi respectiv 8.69%vs. 4.47%, OR 2.13; 95% CI [0.51-8.91], p=0.47).

Lucia Maria Procopciuc1,

Gelu Osian2,

Liviu Vlad2 ,

Ileana Olteanu1

1- Department of Medical Biochemistry, University of Medicine and Pharmacy Cluj- Napoca2- Department of Surgery Clinic III, University of Medicine and Pharmacy Cluj- Napoca

Correspondence to: Lecturer Lucia Maria Procopciuc. E-mail: luciamariaprocopciuc@yahoo.com

Introduction

Colorectal cancer (CRC) is the fourth most common

cancer- related death in the western world and was

ranked third, after lung and breast cancer in Romania in

2001. CRC has a genetic component, implicating

numerous candidate genes as susceptibility

factors(1).

Gene expression patterns, which are controlled by

mechanisms such as DNA methylation, have been

shown to be altered for a number of genes in patients

with different forms of cancer, including CRC (2).

Sporadic CRC appears in about 95% of the cases, the

combination of genetic and environmental risk factors

contributing to its development.

One of the mutated genes implicated in the

carcinogenesis of sporadic CRC could be the gene

encoding the methylenetetrahydrofolate reductase

enzyme (MTHFR). This catalyzes the synthesis of

5-methyltetrahydrofolate (5- MTHF), the methyl donor

for methionine synthesis and the precursor of

S-adenosylmethionine, the universal methyl donor for

methylation reactions (2). Thus, MTHFR is a central

enzyme in the remethylation of homocysteine to

methionine and is important for both DNA methylation

and synthesis (3).

MTHFR is highly polymorphic and the variant

genotypes result in decreased MTHFR enzyme activity

and lower plasma folate levels. The most studied

genetic variant in the MTHFR gene is the 677C >T

polymorphism located in the exon 4, converting alanine

to valine in the mature protein and associated with

reduced enzyme activity and elevated homocysteine

levels (4,5,6,7). The C677T MTHFR polymorphism

influences folate metabolism and intracellular

availability of folate metabolites for DNA methylation

and nucleotide synthesis (8). Individuals carrying the

TT genotype have less folate available for methylation

than CC homozygotes. Homozygous mutant individuals

for the C677T polymorphism have 30% of normal

MTHFR activity (approximately 10% of North

Americans are predisposed to mild

hyperhomocysteinemia and have reduced levels of

DNA methylation) (4). The relationship between the

MTHFR polymorphism and CRC is controversial. Some

researches have shown a reduced risk associated with

the C677T polymorphism but this protective effect

disappears in individuals with low folate intake or high

alcohol consumption (9-13).

Recently, a second common variant in the exon 7 of

the MTHFR gene, A1298C, causing a C to A

substitution, was characterized. This polymorphism

was associated with decreased enzyme activity,

homozygotes having approximately 60% of MTHFR

activity. Heterozygotes for both C677T and A1298C

mutations, approximately 15% of individuals, had

50-60% of MTHFR activity, lower than in single

heterozygotes for the C677T variant (14).

Objectives: We aim to investigate the frequency of

the common C667T and A1298C variants of MTHFR in

Romanian controls and patients with sporadic CRC.

We also want to establish whether these two

polymorphisms represent risk factors for sporadic CRC

in both women and men. We aimed to analyze the

relationship of these two polymorphisms with

histological forms and staging, trying to obtain a

relationship with the prognosis of these cases.

Materials and Methods

1.Patients

In order to test the hypothesis that the two

polymorphisms are implicated in the carcinogenesis of

sporadic CRC, we genotyped these in a case- control

study of 69 patients and 67 healthy controls from the

16

REZUMAT (continuare): Genotipurile AC1298 ºi CC1298 au fost asociate cu un factor de risc de 1.63 (49.27% vs. 37.31%,95% CI [0.82-3.23], p= 0.15) ºi respectiv de 3.00 (4.34% vs. 1.49%, 95% CI [0.3-29.58], p=0.6)de a dezvolta CCR sporadic. 10.14%, OR 2.67, 95%CI [1.02-6.98], p=0.03). Pacienþii pozitivipentru polimorfismele C677T ºi A1298C au dezvoltat cu o frecvenþã mai mare cancer de colonstâng comparativ cu cancerul de colon drept (18.84% vs. 4.34%, OR 5.11, 95%CI [1.38-18.83],p< 0.01, ºi respectiv 23.18% vs. Mai mult, pacienþii pozitivi pentru polimorfismle C677T ºiA1298C au dezvoltat cu o frecvenþã mai mare cancer de colon comparativ cu cancerul de rect(34.78% vs. 18.84%, OR 2.3, 95%CI [1.05-5.01], p= 0.03 ºi respectiv 28.98% vs. 15.94%, OR2.15, 95%CI [0.94-4.92], p= 0.06).Concluzii: Studiul nostru confirmã relaþia dintre genotipurile pentru MTHFR ºi cancerul colorectalsporadic. Indivizii cu risc crescut pot beneficia de metode eficiente de prevenþie ºi tratament cu 5- FU pentru reducerea mortalitãþii prin CCR sporadic.

Received for publication:

16.10.2006

Revised: 20.11.2006

Surgical Clinic III. Of the 69 patients with sporadic CRC,

35 were males (mean age 64.65 years; SD 9.31,

median 64, range 43- 83) and 34 were females (mean

age 61.94 years; SD 10.42, median 62, range 47- 82).

Of the 67 controls, 31 were males (mean age 60.38

years; SD 13.96, median 62, range 26- 78) and 36 were

females (mean age 60.25 years; SD 7.38, median 60.5,

range 43- 73). Eligibility criteria for both cases and

controls were: age 25–85 years; no individual history

of cancer and no familial history of cancer. Controls had

to be free of all polyps at colonoscopy. Indications for

colonoscopy were rectorrhagia, anemia, transit

disorders, subocclusion, occlusion by luminal stenosis,

or tenesmus. Case selection was randomized and the

studied population, Caucasians from the Transylvanian

region, was homogeneous, with a folate-poor diet.

The characteristics of the two groups (age, location

of the tumors, alcohol consumption, smoking status)

are shown in table 1.

Written informed consent was obtained from each

participant in the study and the study was approved by

the Ethical Committee of our University.

2.Methods

Genotyping of C677T and A1298C MTHFR

polymorphisms using PCR- RFLP methods

Genomic DNA was extracted from peripheral blood

leukocytes using the method of Lahiry (15).

Genomic DNA from all participants in this study was

amplified by polymerase chain reaction (PCR) in 25ml

reaction mixture containing 2.0mM magnesium

chloride, 200mM each dNTPs, 0.2mM of each primer,

17

CHARACTERISTICS PATIENTS

(N= 69)

CONTROLS

(N= 67)

Sex

females, number (%)

males, number (%)

34 (49.27%)

35 (50.72%)

36 (53.73%)

31 (46.28%)

Tumor location

Right side, number(%)

Left side, number (%)

Transverse, number (%)

Rectal, number(%)

13 (18.84%)

27 (39.13%)

5 (7.24%)

24 (34.78%)

-

-

-

-

Age (years) ±SD (median)

< 50, number (%)

51- 60, number (%)

61-70, number(%)

> 70 years, number (%)

63.31 ± 8.97

63

6 (8.69%)

22 (31.88%)

21 (30.43%)

20 (28.98%)

59.86 ± 11.91

61

8 (11.94%)

23 (34.32%)

24 (35.82%)

12 (17.91%)

Smoking status

Current smoker, number (%)

Smoker in the past, number(%)

Never smoker, number (%)

16 (23.18%)

3 (4.34%)

50 (72.46%)

16 (23.88%)

3 (4.47%)

48 (71.64%)

Alcohol consumption

yes, number(%)

no, number (%)

38 (55.07%)

31 (44.92%)

42 (62.68%)

25 (37.31%)

Table 1. Clinical characteristics of the two studied groups: patients with sporadic CRC and control individuals

500ng of genomic DNA and 2.0 units of Taq

polymerase (SIGMA). To amplify the polymorphic

C677T region, we used primers 677F 5’-

ACCCACAGAAAATGATGCCCAG-3’ and 677R 5’-

TGCCCCATTATTTAGCCAGGAG- 3’ (4). For the

polymorphic A1298C region of the MTHFR gene, PCR

primers 1298F 5’- CACTTTGTGACCATTCCGGTTT-3’

and 1298R 5’- CTTTGGGGAGCTGAAGGACTA- 3’ were

used (16). PCR was carried out in an Eppendorf

thermocycler with 5 minutes denaturation at 950C,

followed by 30 cycles of denaturation for 30 sec at

940C, annealing for 30 sec at 590C (C677T) or 600C

(A1298C), and extension for 1 min 30 sec at 720C. For

the C677T polymorphism, the amplified fragment was

of 198bp, while for the A1298C polymorphism, the

amplified fragment was of 163bp.

In order to detect the C677T polymorphism, the PCR

product was digested with HinfI restriction enzyme

(New England Biolabs). For the A1298C polymorphism,

the amplified fragment was digested with MboII

restriction enzyme (New England Biolabs). For

enzymatic digestion, 5ml of PCR product, 1ml of buffer

(HinfI or MboII) and 5U of restriction endonuclease

(U/5ml PCR) were mixed and incubated for 3 h at 370C.

Digested DNA products were separated by

electrophoresis in a 3% agarose gel stained with

ethidium bromide. After enzymatic digestion, the

198bp fragment gave for the wild-type allele (C677) an

undigested fragment of 198bp and for the mutated

allele (T677) two fragments of 175 and 23bp (figure 1).

For the wild- type allele (A1298), the 163bp amplified

fragment gave after enzymatic digestion the 84, 31, 30,

28bp fragments, while for the mutated allele (C1298),

the 163bp amplified fragment gave the 56, 31, 30 and

28bp fragments (figure 2).

Statistical analysis

Genotype frequencies were compared using the

chi2 test. Odds ratio (OR) and 95% confidence intervals

(95%CI) were calculated to assess the strength of the

relationship between the C677T and A1298C

polymorphisms and sporadic CRC. We evaluated the

association between MTHFR genotypes and sporadic

CRC first in the entire study population and

subsequently separately in men and women.

18

Figure 2. Restriction analysis of the A1298C MTHFR

polymorphism. Lane 1- pBRHaeIIIDigest DNA molecular marker; Lane

2- 163bp amplified fragment; Lane 3- homozygous negative patient:

fragment of 84bp; Lane 4- heterozygous patient: fragment of 84 and

56bp; Lane 5- homozygous positive patient: fragment of 56bp

Figure 1. Restriction analysis of the C677T MTHFR polymorphism.

Lane 1- pBRHaeIIIDigest DNA molecular marker; Lane 2- 198bp

amplified fragment; Lane 3,4- heterozygous patients: fragments of

198 and 175bp; Lane 5- homozygous negative patients: undigested

fragment of 198bp; Lane 6- homozygous positive patients: fragment

of 175bp

RESULTS

In order to investigate the role of

methylenetetrahydrofolate reductase gene

polymorphisms in sporadic CRC carcinogenesis, we

analyzed the genotypes of C677T and A1298C MTHFR

of 69 patients with this diagnosis and 67 healthy

controls with negative colonoscopy, using a

polymerase chain reaction restriction fragment length

polymorphism method (PCR- RFLP). There was a

difference in genotype distribution and allele frequency

between patients with sporadic CRC and controls. In

patients with sporadic CRC (39 CC homozygotes, 6 TT

homozygotes, 24 CT heterozygotes) the allele

frequency of the T allele was 0.26 compared to 0.17 in

controls (47 CC homozygotes, 3 TT homozygotes, 17

CT heterozygotes). Concerning the A1298C

polymorphism, the results showed that in patients with

sporadic CRC (32 AA homozygotes, 3 CC

homozygotes, 34 AC heterozygotes) the allele

frequency of the C allele was 0.28 compared to 0.2 in

controls (41 AA homozygotes, 1 CC homozygotes, 25

AC heterozygotes) (table 2).

DISCUSION

Sporadic CRC is a multifactorial disease, many

factors contributing to its development, including on

the one hand dietary habits and on the other hand

genetic predisposition (17). Methylenetetrahydrofolate

19

A1298C (Glu ÷ Ala) Allelic frequency

AA (%) AC (%) CC (%) A C

Cases 32 (46.37%)34

(49.27%)3 (4.34%) 0.71 0.28

C677T (Ala÷ Val)

CC (%)

39 (56.52%)17 (24.63%)

20(28.99%)

2 (2.89%)

CT (%)

24 (34.78%)10 (14.49%)

20(28.99%)

2 (2.89%)

TT (%)

6 (8.69%)5 (7.24%) 1 (1.49%) -

Allelic frequencyC 0.73

T 0.26

Controls (N=67) 41 (61.19%)25

(37.31%)1 (1.49%) 0.79 0.2

C677T

(Ala ÷ Val)

CC (%)

47 (70.14%)30 (44.77%)

16(23.88%)

1 (1.49%)

CT (%)

17 25.37%)10 (14.49%) 7 (10.44%) -

TT (%)

3 (4.47%)2(2.98%) 1(1.49%) -

Allelic frequencyC 0.83

T 0.17

Table 2. Alleles and genotypes distribution of C677T and A1298C MTHFR in patients with sporadic

CRC and in control subjects

reductase is a key enzyme in folate metabolism, which

affects DNA synthesis and methylation and is possibly

linked to colorectal carcinogenesis (18). Moreover, the

C677T and A1298C variants have been linked to the

development of most cancers and leukemias (19-21).

Both have been associated with the efficacy and side

effects of cytotoxic drugs like methotrexate and 5-FU

(22,23).

In our study, the CT677 and TT677 genotypes were

greater in patients with CRC compared to controls

(34.78% vs. 25.37%, OR 1.57; 95% CI [0.74-3.28], p=

0.2 and 8.69% vs. 4.47%, OR 2.13 95% CI [0.51-8.91];

p=0.4, respectively). An increased cancer risk was

observed in TT homozygotes. The results were close to

those obtained by Levine (2000) concerning the

association between the TT genotype and the risk for

distal colorectal adenoma (24). The results concerning

the relative risk to develop sporadic CRC in

heterozygotes for the C677T polymorphism were close

to the results obtained by Ryan (2001) (25).

Concerning the second polymorphism, the 1298AC

genotype was associated with an OR of 1.63 (49.27%

vs. 37.31%, 95% CI [0.82-3.23], p= 0.1) for sporadic

CRC, while the CC1298 genotype was associated with

an OR of 3.00 (4.34% vs. 1.49%, 95% CI [0.3-29.58],

p=0.6). The distribution of AC genotype in sporadic

CRC was close to that reported by Toffoli (2003) (26).

Colon cancer occurs with an approximately equal

frequency in men and women (26). Some of the

researches show that the risk of CRC conferred by

MTHFR genotypes may differ between individuals

depending on sex. The analysis of the C677T

polymorphism in women with sporadic CRC vs. control

women indicated that the relative risk to develop

sporadic CRC in heterozygous or homozygous carriers

was1.41 (38.23% vs. 30.55%, 95%CI, [0.52-3.78],

p=0.49) and 2.27 (11.76% vs. 5.55%. 95%CI, [0.38-

13.26], p= 0.6), respectively. The analysis of the

C677T polymorphism in males with sporadic CRC vs.

control males indicated that the relative risk to develop

sporadic CRC in heterozygous or homozygous carriers

was 1.91 (31.42% vs. 19.35%, 95%CI, [0.6- 5.98], p=

0.26) and 1.82 (5.71% vs. 3.22%. 95%CI, [0.15- 21.08],

p= 0.9), respectively.

Concerning the A1298C polymorphism, women

heterozygous or homoyzgous for A1298C MTHFR had a

2.24 (55.88% vs. 36.11%, 95%CI, [0.85- 5.85], p=

0.09) and 1.06 (2.94% vs. 2.77%, 95%CI, [0.06- 17.65],

p= 0.4), respectively increased risk for sporadic CRC.

In heterozygous males patients the relative risk to

develop sporadic CRC was 1.19 (42.85% vs. 38.7%,

95%CI, [0.44- 3.18], p= 0.7). We found homozygotes

for A1298C only among patients with sporadic CRC,

5.71%(table 3).

Some researches have shown that there are

differences concerning the location of the tumors and

the genotype for C677T and A1298C polymorphisms

(26). Our preliminary results showed that patients

positive for C677T and A1298C polymorphisms had a

higher risk to develop colon cancer in the left side than

in the right side (18.84% vs. 4.34%, OR 5.11, 95%CI

[1.38- 18.83], p< 0.01, and 23.18% vs. 10.14%, OR

2.67, 95%CI [1.02-6.8], p= 0.03, respectively).

20

GenotypePatients

69 (50.73%)

Controls

67 (49.26%)OR, 95%IC p

C677T MTHFR (Ala÷ Val)

CT

TT

T677 mutated allele

43.47%

34.78%

8.69%

36 (0.26)

29.85%

25.37%

4.47%

23 (0.17)

1.81 [0.89-3.66]

1.57 [0.74-3.28]

2.13 [0.51-8.91]

0.09

0.2

0.4

A1298C MTHFR (Glu÷ Ala)

AC

CC

C1298 mutated allele

53.62%

49.27%

4.34%

40 (0.28)

38.18%

37.31%

1.49%

27 (0.2)

1.82 [0.92-3.6]

1.63 [0.82-3.23]

3.00 [0.3-29.58]

0.08

0.1

0.6

Table 3. The relative risk to develop sporadic CRC. Comparison between patients and controls

OR- odds ratio; 95%CI- 95% confidence intervals; p- statistical significance means p< 0.05

Moreover, patients positive for C677T and A1298C

polymorphisms had a higher risk to develop colon

cancer than rectal cancer (28.98% vs. 15.94%, OR

2.15, 95%CI [0.94-4.92], p= 0.06 and 34.78% vs.

18.84%, OR 2.3, 95%CI [1.05- 5.01], p= 0.03,

respectively).

The potential interaction between C677T MTHFR and

A1298C MTHFR polymorphisms on the risk of sporadic

CRC was further examined (patients vs. controls). For

individuals carrying both CC677 and AC1298 the OR

was 1.21 (28.99% vs. 23.88%), while the risk increased

to 1.93 in patients with both CC677 and CC1298

(2.89% vs. 1.49%) genotypes. Patients positive for both

CT677 and AC677 had a relative risk of 1.66 (17.39%

vs. 10.44%) to develop sporadic CRC. An increased risk

was observed for patients positive for both TT677 and

AA1298 genotypes, 2.43 (7.24% vs. 2.98%). A

protective effect was observed for patients carrying

both CC677 and AA1298 genotypes, OR 0.56 (24.63%

vs. 43.28%). We found a complete absence of TT677

and CC1298 genotypes; the results were in agreement

with those obtained by Weisberg (1998) and Skibola

(1999) (14, 27).

Regarding the relationship of the C677T genotype

with the Dukes-Mac stage, the study shows that 60%

of stage D patients are patients with the C677T

mutation, present in heterozygous or homozygous

form. The results also show an increase in incidence

for stage D (60%) compared to stage C (34.7%,

p=0.33) and B (46.66%, p=0.71), respectively. In all

cases p>0.05 (table 4).

Regarding the relationship of the A1298C mutation

with cancer staging, our study shows that 70% of

stage D patients are patients with the A1298C

mutation in heterozygous or homozygous form. The

carriers of the A1298C mutation had more frequently

stage D than stage B (70% vs. 60%, p=0.85) and stage

C (70% vs. 26.09%, p=0.04), respectively (table 5).

CONCLUSIONS

Our study showed an association of MTHFR

genotypes with sporadic CRC. We found an elevated

risk of sporadic CRC associated with the heterozygous

and homozygous genotypes of the MTHFR 677>C T

and MTHFR 1298A>C polymorphisms, respectively.

The results confirm the hypothesis that methylation of

DNA may be important in the etiology of sporadic CRC,

because DNA methylation influences cellular

development and function, and aberrations of DNA

methylation are a candidate mechanism for the

development of cancer.

There is evidence that diets low in vegetables and

fiber, with low folate intakes, are associated with an

increased risk for colorectal cancer (29). When folate

levels are low (low intake or depletion by alcohol

consumption) both DNA methylation and synthesis

might be impaired in carriers of MTHFR mutations,

resulting in an increased risk for colorectal cancer (30).

21

Genotype A B C D p

AA 1 (16.66%) 12 (40%) 17 (73.9%) 3 (30) C vs. B- 0.02

AC+ CC 5 (83.33%) 18 (60%) 6 (26.09%) 7 (70%)

B vs. C- 0.01

D vs. C- 0.04

D vs. B- 0.85

Table 5. Relationship of A1298C genotype with Dukes-Mac stage

Genotype A B C D p

CC 3 (50%) 16 (53.3%) 15 (65.2%) 4 (40%)

CT + TT 3 (50%) 14 (46.66%) 8 (34.7%) 6 (60%)D vs. C- 0.33

D vs. B- 0.71

Table 4. Relationship of C677T genotype with Dukes-Mac stage

In our study we have no data on folate intake, but the

population from this geographic area presents several

nutritional risk factors such as high protein and animal

fat and lower fiber diets, lower folate intake, which

reduces the protection conferred by the TT677 and

CC1298 genotypes.

Considerable work has already been focused on

genotype differences in the response to drug

treatments, in order to develop treatment modalities

for individuals identified positive for the C677T and

A1298C mutations. High risk individuals could benefit

from effective prevention and treatment with 5-FU

strategies in order to reduce the mortality of sporadic

colorectal cancer.

Acknowledgments. This study was supported bya grant from the Ministry of Education.

22

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Bucharest - Romania

17th World Congress of the International Association of Surgeons,

Gastroenterologists and Oncologists