Methylenetetrahydrofolate reductase 677C/T gene polymorphism, gastric cancer susceptibility and genomic DNA hypomethylation in an at-risk Italian population

We performed a case-control study to examine the relationship between MTHFR C677T gene polymorphism (MTHFR677C/T) and gastric cancer susceptibility in at-risk populations in central Italy. To explore genomic DNA hypomethylation as a potential etiologic mechanism, this phenomenon was evaluated in carriers of the MTHFR677T/T genotype and carriers of the wild-type MTHFR677C/C genotype. Lymphocyte genomic DNA from 162 gastric cancer patients and 164 controls was used for MTHFR677C/T genotyping. Unconditional regression analysis with ORs and 95% CIs was used to investigate the association of the polymorphism with disease. Genomic DNA methylation status by an established enzymatic assay that measures the DNA accepting capacity of methyl groups (inversely related to endogenous methylation) was assessed in a random sample of 40 carriers of the wild-type MTHFR677C/C genotype and 40 carriers of the MTHFR677T/T genotype. The global allelic distribution was in Hardy-Weinberg equilibrium. The MTHFR677T allele was significantly associated with gastric cancer risk with an OR of 2.49 (95% CI 1.48-4.20) in heterozygous MTHFR677C/T carriers and an OR of 2.85 (95% CI 1.52-5.35) in homozygous MTHFR677T/T carriers. This risk association was retained in subgroup analyses by tumor histotype and location. Genomic DNA hypomethylation status in MTHFR677T/T carriers was significantly higher than in subjects with wild-type MTHF677C/C genotype (p = 0.012). In the studied population, MTHFR677T played the role of a moderate-penetrance gastric cancer susceptibility allele. Possession of the MTHFR677T/T genotype was significantly associated with genomic DNA hypomethylation. These findings deserve further investigation in the context of novel strategies for gastric cancer prevention.     

Colorectal cancer and polymorphism of methylenetetrahydrofolate reductase (C677T) in Morocco

Introduction

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate metabolism. It is involved in the synthesis, repair, and methylation of deoxyribonucleic acid (DNA). The most frequently studied MTHFR gene polymorphism is C677T, which is involved in the pathogenesis of many diseases including cancer. This case-control study was undertaken to analyze the association of MTHFR C677T polymorphism and the risk of colorectal cancer (CRC).

Methods

We determined the genotypes and alleles of MTHFR gene in 36 patients with histological confirmed CRC (19 women and 17 men) and in 36 normal controls matched for sex without a history of cancer. DNA was isolated from peripheral blood samples, and genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

Results

In light of our results, the association of combined CT and TT genotypes and T allele was associated with an increased risk of CRC odds ratio 6.88 [95% confidence interval (CI): 2.30?C20.49, P = 0.0005), 5.91 (95% CI: 2.14?C16.34, P = 0.0006), and 2.96 (95% CI: 1.4?C6.25, P = 0.0045), respectively. TT homozygous was not a protective factor in our study with an odds ratio of 2.36 (95% CI: 0.63?C17.65, P = 0.16). Relative risk, individuals carrying at least one T allele have a 2-fold greater risk of developing CRC.

Conclusion

The MTHFR C677T gene variant was a risk factor for CRC in our population under study.     

亚甲基四氢叶酸还原酶基因 C677T多态性与胃癌患者对 5-FU化疗敏感性的关系

背景和目的:亚甲基四氢叶酸还原酶( methylenetetrahydrofolate reductase,MTHFR)基因变异影响 MTHFR的活性,以致影响体内 5, 10-MTHF的浓度,从而影响 5-FU的抗瘤活性.本研究旨在观察 MTHFR基因 C677T多态性对预测胃癌患者对 5-FU的敏感性和化疗毒性的影响.方法:收集经病理学确诊的晚期胃癌 75例.所有病例化疗前抽外周静脉血 2 ml,用 PCR-RFLP技术检测研究对象的 MTHFR 基因型.基因型分为野生型纯合子 (C/ C)、杂合子 (C/ T)、变异型纯合子 (T/ T)3种类型.所有患者经含 5-FU为基础的联合化疗方案化疗.结果: 75例晚期胃癌患者中, MTHFR C/ C基因型 24例( 32.0%), MTHFR C/ T基因型 33例( 44.0%), MTHFR T/ T基因型 18例( 24.0%).其中 22例 PR, 29例 NC, 24例 PD,化疗总有效率 29.3%. MTHFR T/ T基因型患者的化疗有效率( 20/24, 83. 3%)明显高于 MTHFR C/ C基因型患者( 2/24, 8. 3%)(χ 2=24. 01, P< 0. 001),同样高于 MTHFR C/ T基因型患者( 5/33, 15. 2%)(χ 2=22. 7, P< 0. 001). MTHFR C/ C基因型患者的化疗有效率与 MTHFR C/ T基因型患者之间无显著性差异(χ 2=0. 6, P=0. 439).非条件多元 Logistic 回归分析(调整性别、年龄、化疗方案、辅助化疗因素的影响)结果显示 C/ C+ C/ T基因型患者对化疗有效的可能性为 T/ T基因型患者的 0. 017倍( 95% CI: 0. 003～ 0. 102,P< 0. 001). T/ T基因型患者的恶心呕吐反应显著高于 C/ C、 C/ T基因型患者(χ 2=12.264,P=0.002).结论: MTHFRC677T基因型对预测以 5-FU为基础化疗方案治疗晚期胃癌的疗效和毒性具有较好的临床意义.     

MTHFR基因C677T和A1298C多态性与肺癌的关系

目的:通过对广东地区汉族肺癌患者和正常人群中MTHFRC677T和A1298C基因多态性分布检测,探讨与肺癌之间的关系。方法:研究分肺癌组和正常对照组各100例,分别利用PCR进行两组MTHFR基因多态性的检测。结果:肺癌组和对照组中MTHFRC677T各基因亚型的分布有显著性差异(χ2=7.002,P=0.030),其中CC基因亚型在两组之间的分布有显著性差异(χ2=5.214,P=0.022),CT基因亚型无显著性差异(χ2=0.320,P=0.572),TT基因亚型也有显著性差异(χ2=4.013,P=0.045),而MTHFRA1298C基因多态性分布在肺癌病例与正常人之间的分布无明显变化,统计学上无显著性差异(χ2=0.098,P=0.952)。结论:MTHFR基因C677T在肺癌病例与正常人之间的分布有所不同,有助于从分子遗传学角度发现肺癌的高危人群,从而对人群进行筛选。     

Methylenetetrahydrofolate reductase polymorphism C677T is not associated to the risk of cervical dysplasia

The aim of the study was to explore a possible association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and cervical neoplasia. A total of 229 women were subjected to cytologic and colposcopic evaluation. Ninety-one of them were found to be normal, and served as the control group, while the other 138 of them had present or past histologically proven cervical pathology (patients group). All patients and controls were investigated for the MTHFR C677T polymorphism. Statistical analysis between the groups of cases with cervical intraepithelial neoplasia or invasive cervical cancer and the control group did not reveal any statistically significant difference in the frequency of the MTHFR C677T polymorphism.     

Effect of the methylenetetrahydrofolate reductase C677T polymorphism on patients with cisplatin/gemcitabine-treated stage IV non-small-cell lung cancer

Single nucleotide polymorphisms (SNPs) in the metabolic pathways of S-adenosylmethionine have been related to global hypomethylation and a lower number of hypermethylated CpG islands of tumor suppressor genes. Hypermethylation of checkpoint and DNA repair genes has been shown to be indicative of chemosensitivity. In the present study, we have examined the SNP of methylenetetrahydrofolate reductase (MTHFR) C677T, which affects DNA methylation patterns and is linked to elevated plasma homocysteine levels in 208 patients with gemcitabine/cisplatin-treated stage IV non-small-cell lung cancer (NSCLC). No differences in response rate were observed according to the MTHFR genotype. However, time to progression was 7.4 months for 68 patients with CC genotype, 5.5 months for 108 patients with heterozygous CT genotype, and 5.2 months for 28 patients with TT genotype. These findings can lead us to distinguish different outcome patterns among patients with stage IV NSCLC whose similar clinical prognostic factors would otherwise indicate similar outcomes. Carriers of the MTHFR 677T allele could benefit from supplementation with folic acid and vitamin B12. The Spanish Lung Cancer Group has undertaken a phase III randomized trial to elucidate this concept.     

Folate restriction and methylenetetrahydrofolate reductase 677T polymorphism decreases adoMet synthesis via folate-dependent remethylation in human-transformed lymphoblasts.

The homozygous mutation (677TT) in the methylenetetrahydrofolate reductase (MTHFR) gene reduces enzyme activity and alters cellular folate composition. Previous epidemiological studies reported a potential protective effect of MTHFR677C --> T against acute lymphocytic leukemia and malignant lymphoma, but the mechanism remains to be determined. We investigated the biochemical impacts of MTHFR677C --> T on cellular S-adenosyl methionine (adoMet) synthesis, global DNA methylation, and de novo purine synthesis, all of which are potential regulatory pathways involved in tumorigenesis. Metabolic fluxes of homocysteine remethylation and de novo purine synthesis were compared between Epstein-Barr virus-transformed lymphoblasts expressing MTHFR 677C and MTHFR 677T using stable isotopic tracers and GCMS. MTHFR TT genotype significantly reduced folate-dependent remethylation under folate restriction, reflecting limited methylated folates under folate restriction. Data also suggested increased formylated folate pool and increased purine synthesis when folate is adequate. The impacts of MTHFR 677T polymorphism appeared closely related to folate status, and such alterations may modulate metabolic pathways involved in cancer onset/progression. The advantage of de novo purine synthesis found in the MTHFR TT genotype may account for the protective effect of MTHFR in hematological malignancies. These transformed cells are potential models for studying the consequences of human genetic variation and cancer pathogenesis.     

Reduced breast cancer risk with increasing serum folate in a case-control study of the C677T genotype of the methylenetetrahydrofolate reductase gene

Breast cancer risk may be associated with folate status or the C677T genotype of the methylenetetrahydrofolate reductase (MTHFR) gene. We compared serum folate concentrations and C677T genotype in 141 breast cancer patients and 109 age-matched controls. Serum folate was significantly lower in cases compared to controls (geometric means, 5.7 versus 6.6 microg/l; P=0.005). Breast cancer risk was not associated with C677T genotype. After adjusting for age of menarche, parity, alcohol intake and total fat intake we observed reductions in odds ratios for breast cancer risk comparing the highest with the lowest quartiles of serum folate concentrations of 0.23 (95% confidence interval (CI) 0.09, 0.54) for the entire group, 0.27 (CI 0.09, 0.80) for the wild-type and 0.08 (CI 0.01, 0.52) for the heterozygous C677T genotype. We conclude that for the whole group, and the wild-type and heterozygous C677T genotypes, increased serum concentrations of folate were associated with reduced risks of breast cancer.     

Influence of methylenetetrahydrofolate reductase gene polymorphisms C677T and A1298C on age-associated risk for colorectal cancer in a caucasian lynch syndrome population.

Lynch syndrome is caused by germ-line mutations in the DNA mismatch repair (MMR) genes; mutation carriers are predisposed to a variety of cancers, most commonly colorectal and endometrial. The median age of colorectal cancer onset is 45 years and the lifetime risk is approximately 80%, but the onset age varies substantially. It is likely that other low-penetrance genes and environmental factors act as modifiers of the risk associated with the highly penetrant MMR gene mutations. Methylenetetrahydrofolate reductase plays a key role in folate metabolism. We investigated the association of C677T and A1298C, two common polymorphisms in the methylenetetrahydrofolate reductase gene, with risk for early onset colorectal cancer in Lynch syndrome. Subjects were 185 non-Hispanic whites with confirmed DNA MMR mutations. Kaplan-Meier estimates for the age at colorectal cancer onset according to C677T genotypes were significantly different for the CT and TT genotypes compared with the wild-type CC (P = 0.014, log-rank test; P = 0.004, trend test). The median ages at onset were 43 years for the CC genotype and 39 years for the combined CC and CT genotypes and the CC+CT genotypes were associated with a reduced age-associated risk for developing colorectal cancer (hazard ratio, 0.55; 95% confidence interval, 0.36-0.85). No differences in ages at onset or risk were found for the A1298C genotypes. This is the first report to our knowledge to provide evidence that the C677T polymorphism modifies the age at onset of colorectal cancer in Caucasian Lynch syndrome subjects with the 677T allele having a protective effect.     

Normal frequencies of the C677T genotypes on the methylenetetrahydrofolate reductase (MTHFR) gene among lymphoproliferative disorders but not in multiple myeloma

The folate availability seems to be critical for the DNA integrity since it is required for the transfer of methyl groups in the biosynthesis of thymidilate. Although the excessive incorporation of uracils to the DNA can be efficiently removed, this mechanism of reparation produces many double-strand breaks from two opposing nicks. Several chromosomal abnormalities (mainly translocations and deletions perhaps not well understood) are involved in the origin of lymphoproliferative disorders. The TT homozygosity at nucleotide 677 in the gene of methylene tetrahydrofolatereductase (MTHFR), a key enzyme in folate metabolism, was recently linked to a significant protection against colon carcinoma and acute lymphoblastic leukaemia in adults. We analysed the genotype frequencies of C677T-MTHFR in a group of 143 patients with lymphoproliferative disorders (REAL classification) and 200 controls. Overally, the frequencies of the polymorphic allele were similar (35.3% and 32.0% respectively)(P=0.6). We did not find differences between patients and controls except for myeloma/plasmacytoma group (n=26) which showed a CC genotype less than expected (19% vs 46%) (p=0.01) with a frequency ratio of 0.28 (0.10-0.77). Even among the IgG myeloma cases only one patient showed a common genotype (CC) (1/15, 7%) (P=0.003). If these preliminary data are validated with prospective studies, the 677C allele of MTHFR gene could be confirmed as an effective multiple myeloma protective factor (specially for the IgG cases).     

Methylenetetrahydrofolate reductase C677T polymorphism does not alter folic acid deficiency-induced uracil incorporation into primary human lymphocyte DNA in vitro.

Methylenetetrahydrofolate reductase (MTHFR) is an enzyme which converts 5,10-methylene tetrahydrofolate (5,10-MnTHF) to 5-methyl tetrahydrofolate. A common C to T transition (C677T) in the MTHFR gene is reported to reduce the risk for colorectal cancer and acute lymphocytic leukemia in homozygotes (TTs). It is hypothesized that because TTs have reduced MTHFR activity, more 5,10-MnTHF is available to provide methyl groups for the conversion of uracil to thymidine. Folic acid deficiency causes the intracellular accumulation of dUMP and the subsequent incorporation of uracil into DNA. The removal of uracil from DNA may result in double-stranded DNA breaks, the accumulation of which is a putative risk factor for cancer. We tested whether human lymphocytes taken from TTs (n = 10) were more able to resist uracil incorporation into DNA than controls (n = 14 CCs and 6 CTs) when cultured in medium containing 12-120 nM folic acid for 9 days. DNA uracil content of these lymphocytes was measured by CG-MS. TTs and controls showed a dose-dependent increase in DNA uracil content during folic acid deficiency (P < 0.0001, R2 = 0.23 for TTs and P < 0.0001, R2 = 0.19 for controls). DNA uracil content was not different between the two groups at any of the folic acid concentrations (two-way ANOVA: media [folic acid], P < 0.0001; genotype, P = 0.4). The results show that, in this in vitro system, the MTHFR C677T polymorphism does not affect the cell's ability to resist uracil incorporation into DNA. Chromosome breakage, as measured by micronuclei, was also shown to correlate with folic acid concentration in a preliminary experiment (P < 0.0001). Although the results appear not to support the hypothesis that a reduced risk for certain cancers in TTs is due to diversion of folic acid to thymidine synthesis, differences between the in vivo and in vitro situation make this conclusion not definitive.     

Associations between two common variants C677T and A1298C in the methylenetetrahydrofolate reductase gene and measures of folate metabolism and DNA stability (strand breaks, misincorporated uracil, and DNA methylation status) in human lymphocytes in vivo.

OBJECTIVE: Homozygosity for variants of the methylenetetrahydrofolate reductase (MTHFR) gene is associated with decreased risk for colorectal cancer. We have investigated the relationships between two variants of the MTHFR gene (C677T and A1298C) and blood folate, homocysteine, and genomic stability (strand breakage, misincorporated uracil, and global cytosine methylation in lymphocytes) in a study of 199 subjects. RESULTS: The frequencies of homozygosity for the C677T and A1298C variants of the MTHFR gene were 12.6% and 14.6%, respectively. Plasma homocysteine, folate, vitamin B12, 5-methyltetrahydrofolate, and RBC folate were determined in the C677T genotypes. Plasma folate was significantly lower (P < 0.001) in the homozygous variants (6.7 +/- 0.6 ng/mL) compared with wild-types (8.8 +/- 0.4 ng/mL) and heterozygotes (9.1 +/- 0.5 ng/mL). Homocysteine was significantly higher (P < 0.05) in homozygous variants (13.2 +/- 1.1 micromol/L) compared with homozygous subjects (10.9 +/- 0.4 micromol/L). Homozygous variants had significantly lower (P < 0.05) RBC folate (84.7 +/- 6.3 ng/mL) compared with wild-types (112.2 +/- 5.2 ng/mL) and heterozygous individuals (125.1 +/- 6.6 ng/mL). No significant difference in RBC folate was observed between wild-types and heterozygotes. The A1298C variant did not influence plasma homocysteine, folate, 5-methyltetrahydrofolate, vitamin B12, or RBC folate. Lymphocyte DNA stability biomarkers (strand breaks, misincorporated uracil, and global DNA methylation) were similar for all MTHFR C677T or A1298C variants. CONCLUSION: Data from this study do not support the hypothesis that polymorphisms in the MTHFR gene increase DNA stability by sequestering 5,10-methylenetetrahydrofolate for thymidine synthesis and reducing uracil misincorporation into DNA.     

Genetic susceptibility of methylenetetrahydrofolate reductase (MTHFR) gene C677T, A1298C, and G1793A polymorphisms with risk for bladder transitional cell carcinoma in men

We performed a case-control study of 158 bladder transitional cell carcinoma (TCC) cases and 316 controls to investigate the association between methylenetetrahydrofolate reductase (MTHFR) C677T, A1298G, and G1793A polymorphisms and bladder cancer susceptibility by polymerase chain reaction restriction fragment length polymorphism (PCR-RLFP) technique. The controls were frequency-matched to the cases by age (± 5 years), ethnicity, and smoking status. We also measured serum levels of total homocysteine (tHcy), folate, and vitamin B12. It was found that the 1298AC (odds ratio, OR = 3.74; 95% confidence interval, CI = 2.34-5.47; P = 0.001) and 1298CC (OR = 3.46, 95% CI = 2.37-5.52; P = 0.001) genotypes of MTHFR A1298C were significantly associated with increased risk of bladder TCC. The MTHFR C677T and G1793A polymorphisms were not associated with bladder TCC. After stratification for grade and stage, we observed that the 677TT (OR = 4.47, 95% CI = 2.74-6.72; P = 0.001) and MTHFR 1298CC (OR = 4.78, 95% CI = 2.82-6.89; P = 0.001) genotypes of MTHFR were associated with increased risk of muscle-invasive bladder TCC. We also found that the MTHFR 677CT+1298AA genotypes were associated with an approximately 70% reduction in risk of bladder cancer (OR = 0.31; 95% CI = 0.15-0.68) compared to the combined referent genotype. There were 8 haplotypes and 16 haplotype genotypes based on these three variants. When we used the haplotypes and assumed that the 677T, 1298C, and 1793G alleles were risk alleles, the adjusted odds ratios increased as the number of risk alleles increased: 1.00 for 0-1 variant, 1.88 (1.4-2.7) for any two risk alleles and 2.07 (1.6-2.8) for any three risk alleles. Serum tHcy levels were significantly higher in carriers of the 677T, 1298C, and 1793G alleles compared to noncarriers (all P < 0.01). There was no significant correlation between serum levels of tHcy and folate and bladder cancer risk. Further studies in larger samples size and different ethnicity are required to confirm our findings.     

Multiplex PCR for simultaneous detection of 677 C-->T and 1298 A-->C polymorphisms in methylenetetrahydrofolate reductase gene for population studies of cancer risk

Methylenetetrahydrofolate reductase (MTHFR) plays a pivotal role in folate metabolism by regulating the diversion of folate metabolites toward DNA methylation or toward DNA synthesis. Because aberrations in both of these pathways can be tumor promoting, the two common polymorphisms in the MTHFR gene, 677 C-->T and 1298 A-->C, have been implicated as risk factors for several cancers. Homozygosity for the 677 C-->T polymorphism and compound heterozygosity for 677 C-->T and 1298 A-->C polymorphisms both reduce enzyme activity by more than 50% and can promote oncogenic alterations in DNA methylation especially when folate status is low. Thus, rapid identification of both polymorphisms in MTHFR gene would be of importance in understanding the genetics of abnormal folate metabolism as related to human cancer risk. Here we describe a multiplex polymerse chain reaction/restriction fragment length polymorphism procedure in which two sets of primers are used to amplify simultaneously the DNA regions spanning 677 and 1298 loci in one PCR reaction. The amplified products are digested by HinfI or MboII followed by agarose gel electrophoresis for simultaneous detection of the 677 C-->T and 1298 A-->C polymorphisms in the same gel.     

Colorectal cancer and the methylenetetrahydrofolate reductase 677C -> T and methionine synthase 2756A -> G polymorphisms: a study of 2,168 case-control pairs from the JANUS cohort.

Polymorphisms in genes involved in the metabolism of folate and methyl groups have been implicated with risk of colorectal cancer. We evaluated the relation between the polymorphisms 677C --> T of the methylenetetrahydrofolate reductase (MTHFR) and 2756A --> G of the methionine synthase (MTR) genes and risk of colorectal cancer. From the Norwegian JANUS cohort of 309,000 subjects, 2,179 cases were identified and a similar number of controls were selected. The controls were matched for age, gender, time, and place of serum donation. Genotypes were obtained from 2,168 case-control pairs by real-time PCR of serum samples. Risk of colorectal cancer was estimated with conditional and unconditional logistic regression. Median age at diagnosis was 60 years and mean follow-up 13 years. The odds ratio for MTHFR TT versus CC was 0.73 [95% confidence interval (95% CI), 0.58-0.92] and for MTR GG versus AA was 0.65 (95% CI, 0.47-0.90). No interaction between the polymorphisms was found. Relative risk estimates were similar for men and women, and for young and old age at diagnosis. For the MTR GG genotype, risk reduction was observed at the two most distal sites (sigmoideum and rectum) only (P = 0.003). The folate marker, serum total homocysteine (tHcy), was measured in 1,837 subjects. Odds ratio for the upper versus the lower tertile of tHcy was 1.32 (95% CI, 1.04-1.68). No significant effect modification by tHcy levels was detected for either polymorphism. In summary, we found significantly reduced risk of colorectal cancer in subjects with the MTHFR 677 TT and MTR 2756 GG genotypes. No interaction between the polymorphisms, or of either polymorphism with tHcy, was detected.     

The methylenetetrahydrofolate reductase C677T mutation induces cell‐specific changes in genomic DNA methylation and uracil misincorporation: A possible molecular basis for the site‐specific cancer risk modification

The C677T polymorphism in the methylenetetrahydrofolate reductase (MTHFR) gene is associated with a decreased risk of colon cancer although it may increase the risk of breast cancer. This polymorphism is associated with changes in intracellular folate cofactors, which may affect DNA methylation and synthesis via altered one‐carbon transfer reactions. We investigated the effect of this mutation on DNA methylation and uracil misincorporation and its interaction with exogenous folate in further modulating these biomarkers of one‐carbon transfer reactions in an in vitro model of the MTHFR 677T mutation in HCT116 colon and MDA‐MB‐435 breast adenocarcinoma cells. In HCT116 cells, the MTHFR 677T mutation was associated with significantly increased genomic DNA methylation when folate supply was adequate or high; however, in the setting of folate insufficiency, this mutation was associated with significantly decreased genomic DNA methylation. In contrast, in MDA‐MB‐435 cells, the MTHFR 677T mutation was associated with significantly decreased genomic DNA methylation when folate supply was adequate or high and with no effect when folate supply was low. The MTHFR 677T mutation was associated with a nonsignificant trend toward decreased and increased uracil misincorporation in HCT116 and MDA‐MB‐435 cells, respectively. Our data demonstrate for the first time a functional consequence of changes in intracellular folate cofactors resulting from the MTHFR 677T mutation in cells derived from the target organs of interest, thus providing a plausible cellular mechanism that may partly explain the site‐specific modification of colon and breast cancer risks associated with the MTHFR C677T mutation. © 2008 Wiley‐Liss, Inc.     

Association of the C677T polymorphism in the MTHFR gene with breast and/or ovarian cancer risk in Jewish women

The C677T mutation in the methylenetetrahydrofolate reductase (MTHFR) gene is associated with reduced enzyme activity, hyperhomocysteinaemia and increased risk for atherosclerosis in homozygotes. We examined the frequency of this mutation and its association with disease pattern in 491 Jewish women with either sporadic (n=355; 72%) or hereditary (n=136; 28%) breast and/or ovarian cancer and in 69 asymptomatic BRCA1/2 mutation carriers, genotyped for the three predominant Jewish founder BRCA1/2 mutations (185delAG, 5382insC and 6174delT). 677T homozygotes were equally distributed among women with sporadic breast and/or ovarian cancer (71/355; 20.0%) and among BRCA1/2 mutation carriers (43/205; 21.0%) (P=non-significant). 677T homozygotes were equally distributed among women diagnosed with breast cancer prior to (22/122; 18.0%) and after 42 years of age (42/243; 17.3%). Among BRCA1/2 carriers, the rate of 677T homozygotes in manifesting cancer (32/136; 23.5%) and asymptomatic individuals (11/69; 15.9%) was not significantly different. The rate of 677T homozygotes (24/72; 33.3%) was higher (P=0.0026) among women with bilateral breast cancer and those with both breast and ovarian carcinoma than among those with unilateral breast cancer (64/365; 17.5%). Differences in morbidity (one versus multiple breast/ovarian tumours) are mainly attributed to 677T homozygosity and partly to BRCA1/2 mutations. Confirmation of these data, namely, that the 677T allele is significantly more common in cases of bilateral breast cancer or combined breast and ovarian cancer would have important clinical implications.