Methylenetetrahydrofolate reductase 677 C-->T polymorphism and risk of proximal colon cancer in north Italy.

PURPOSE: Gene silencing by hypermethylation plays an important role in proximal colon carcinogenesis. Conversely, DNA hypomethylation has been associated with distal colon cancer (CLC). Methylenetetrahydrofolate reductase (MTHFR) catalyzes the conversion of 5',10'-methylenetetrahydrofolate to 5'-methyl tetrahydrofolate, which serves as methyl donor in the remethylation of homocysteine to methionine. A common MTHFR 677 C-->T polymorphism is characterized by reduced catalytic activity, which affects methionine synthesis and DNA methylation. The aim of the study was to investigate the role of MTHFR 677 C-->T gene polymorphism in the tumorigenesis of proximal and distal CLC in a monoinstitutional group of patients in North Italy. EXPERIMENTAL DESIGN: One-hundred thirty four consecutive proximal and 142 consecutive distal CLC patients, and 279 control subjects without cancer were genotyped for MTHFR using PCR-restriction fragment-length polymorphism analysis. RESULTS: The prevalence of the 677 TT genotype was significantly (P = 0.005) lower in patients with proximal tumors (10 of 134, 7%) than in subjects with distal tumors (28 of 142, 20%). Case/control approach indicated that individuals homozygous for the 677 TT allele had a significantly reduced risk (2.8-fold) (adjusted odds ratio, 0.36; 95% confidence intervals, 0.14-0.91) of developing proximal CLC compared with those harboring the wild-type or heterozygous genotype (677 CC or 677 CT). No significant association between CLC risk and TT genotype was observed in patients with distal tumors (odds ratio, 1.01; 95% confidence interval, 0.48-2.14). CONCLUSIONS: Our findings support a role for MTHFR 677 TT genotype in reducing proximal CLC risk in North Italy.     

Breast cancer risk and methylenetetrahydrofolate reductase polymorphism

Objective. Methylenetetrahydrofolate reductase (MTHFR), a polymorphic enzyme involved in folate metabolism, plays a role in DNA biosynthesis, methylation, and repair in actively dividing cells. Because breast-cell division occurs in women with active ovulatory cycles, polymorphisms in the MTHFR gene could be a risk factor for breast cancer. Methods. We genotyped 352 clinic-based study subjects for MTHFR, 105 subjects with breast cancer and 247 with benign breast disease, histopathologically classified as high-risk or low-risk for breast cancer. Questionnaire data were collected prior to biopsy to blind subjects and interviewers to diagnoses. Results. Premenopausal women with the MTHFR polymorphism had a threefold increased breast cancer risk (OR = 2.8; 95%CI: 1.02–7.51) compared to the clinic-based controls with benign breast disease. Results were similar using either low- or high-risk controls. However, risk for postmenopausal women was not elevated (OR = 0.8; 95%CI 0.4–1.4). No significant interaction between genotype and smoking or alcohol was found, but polymorphic MTHFR decreased the likelihood of drinking alcohol (OR = 0.5; 95%CI 0.3–0.9). Conclusion. These data suggest that polymorphic MTHFR increases risk of premenopausal, but not postmenopausal, breast cancer. These findings should be explored with a larger sample size in order to analyze gene–environment interactions between MTHFR and folate. Once the intricate relationship between diet and breast cancer has been elucidated, new cancer control initiatives can be considered such as folate chemoprevention trials in high-risk individuals.     

Genetic polymorphisms of methylenetetrahydrofolate reductase and colorectal cancer and adenoma

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme regulating folate metabolism, which affects DNA methylation and synthesis. Two functional, common polymorphisms (C677T and A1298C) are known in the MTHFR gene. MTHFR activity is lowered in individuals with the 677TT genotype and is somewhat reduced in those with the 1298CC genotype. We reviewed the consistency of reported associations of these polymorphisms with colorectal cancer and adenoma with consideration of the effects of nutritional status. A total of 16 studies have addressed the association between MTHFR C677T polymorphism and colorectal cancer in 10 countries. Decreased risk of colorectal cancer associated with the 677TT genotype has fairly consistently been observed, with few exceptions. This decrease was observable in people with either high or low folate status. Alteration in the thymidylate pool associated with MTHFR activity is postulated as an underlying mechanism. Studies on the A1298C polymorphism are limited, and their results are variable. Almost all of seven studies of colorectal adenoma have found no association between C677T polymorphism and adenoma, but the 677TT genotype seems to be related to increased risk when folate status is poor. Reduced availability of methyl groups for DNA methylation might be more relevant to adenoma formation. Although the underlying mechanisms still remain to be clarified, epidemiological findings regarding MTHFR C677T polymorphism provide strong evidence that adequate folate status confers protection from colorectal cancer.     

A prospective study of methylenetetrahydrofolate reductase and methionine synthase gene polymorphisms, and risk of colorectal adenoma

We examined the relationship between a functional polymorphism (667C-- >T, ala-->val) of the methylenetetrahydrofolate reductase gene (MTHFR) and the risk of colorectal adenomas in the prospective Nurses' Health Study. Among 257 incident polyp cases and 713 controls, the MTHFR val/val polymorphism [relative risk (RR) = 1.35, 95% confidence interval (CI) 0.84-2.17] was not significantly associated with risk of adenomas. This lack of association was observed for both small (RR = 1.36, 95% CI 0.76-2.45) and large (RR = 1.32, 95% CI 0.66-2.66) adenomas. Furthermore, there was no significant interaction between this polymorphism and consumption of either folate, methionine or alcohol. We also examined the relationship of a newly identified polymorphism (asp919gly) of the methionine synthase gene (MS) with the risk of colorectal adenomas in the same population. The MS gly/gly polymorphism was also not significantly associated with risk of colorectal adenomas (RR = 0.66, 95% CI 0.26-1.70). These results, which need to be confirmed in other studies, suggest that the MTHFR val/val polymorphism, which has been previously inversely associated with risk of colorectal cancer, plays a role only in a late stage (adenoma-- >carcinoma) of colorectal tumorigenesis, and/or may protect against malignant transformation in the subset of benign adenomas, which may progress to malignancy.      

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多态性与食管癌易感性的关系

目的　研究亚甲基四氢叶酸还原酶 (MTHFR)基因C6 77T多态性及其和烟酒茶嗜好相互作用与食管癌易感性的关系。方法　在上消化道癌高发区淮安市进行了一个病例 对照研究 (食管癌 93例 ,人群对照 2 0 0例 ) ,调查研究对象的生活习惯 ,采用PCR RFLP技术检测研究对象的MTHFR基因型。结果　 1.食管癌组和对照组中MTHFR变异型等位基因携带者分别占 6 6 .7%和 6 8.5 % ,其差异无统计学显著性。 2 .在MTHFR野生型基因携带者中 ,吸烟习惯显著增加食管癌发生的危险性 (OR =3.2 2 ,95 %CI:1.0 9～ 9.5 3)。在MTHFR变异型基因携带者中 ,经常饮酒者发生食管癌的危险性显著升高 (OR =2 .30 ,95 %CI :1.0 2～ 2 .5 7)。在野生型和变异型基因携带者中 ,有饮茶习惯者发生食管癌的危险性均显著降低。结论　MTHFR基因的多态性影响吸烟、饮酒与食管癌之间的关系。调查生活习惯、同时检测MTHFR基因型有助于食管癌的预防。     

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.     

The polymorphism of methylenetetrahydrofolate reductase C677T but not A1298C contributes to gastric cancer

Increasing epidemiological studies have revealed the important role of methylenetetrahydrofolate reductase (MTHFR) in carcinogenesis. The association of MTHFR A1298C and MTHFR C677T polymorphisms with the risk for gastric cancer remains obscure due to inconsistent findings in independent studies among diverse ethnicities. A meta-analysis based on all available publications on this genetic association was performed. The pooled odds ratios (ORs) with 95 % confidence intervals (95 % CIs) were calculated to estimate the effect of MTHFR variants on gastric carcinogenesis. Totally, 25 eligible case–control studies were included into the meta-analysis according to the inclusion criteria. The MTHFR C677T polymorphism was demonstrated to significantly increase the susceptibility to gastric cancer (OR_{T vs. C}?=?1.21, 95 % CI 1.10–1.34; OR_{TT vs. CC}?=?1.47, 95 % CI 1.22–1.76; OR_{TC vs. CC}?=?1.20, 95 % CI 1.03–1.40; OR_{TT + TC vs. CC}?=?1.27, 95 % CI 1.10–1.47; OR_{TT vs. CC + TC}?=?1.29, 95 % CI 1.15–1.46), whereas no significant correlation was observed when assessing the MTHFR A1298C polymorphism (OR_{C vs. A}?=?1.00, 95 % CI 0.90–1.10; OR_{CC vs. AA}?=?0.99, 95 % CI 0.75–1.31; OR_{CA vs. AA}?=?1.01, 95 % CI 0.89–1.14; OR_{CC + CA vs. AA}?=?1.00, 95 % CI 0.89–1.13; OR_{CC vs. AA + CA}?=?0.97, 95 % CI 0.74–1.27). Subgroup analyses by ethnicity and source of controls further confirmed the findings in overall analysis. The meta-analysis suggests that the polymorphism of MTHFR C677T but not MTHFR A1298C confers a risk effect on the development of gastric cancer among Asians and Caucasians, which provides a new insight into the gastric cancer pathogenesis.     

Methylenetetrahydrofolate reductase polymorphism and risk of colorectal adenomas

A homozygous mutation at bp 677 in the gene for the methylenetetrahydrofolate reductase (MTHFR) was previously shown to be associated with a decreased risk of colorectal cancer. We examined the relation between the MTHFR genetic polymorphism and risk of colorectal adenoma in Japanese men using 205 cases of colorectal adenomas and 220 controls of normal total colonoscopy. The homozygous mutation was not measurably associated with colorectal adenomas. The findings corroborate the lack of an association between the MTHFR genotype and colorectal adenomas, but do not deny the possibility that the genotype may be involved in the late stage of colorectal carcinogenesis.     

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.     

Methylenetetrahydrofolate reductase C677T polymorphism and cervical cancer risk: a meta-analysis

Background: Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in the metabolism of folate,and the role of MTHFR C677T polymorphism in cervical carcinogenesis is still controversial. Method: Weperformed a meta-analysis of all relevant case-control studies that examined any association between the C677Tpolymorphism and cervical cancer risk. We estimated summary odds ratios (ORs) with their confidence intervals(CIs) to assess links. Results: Finally, 10 studies with a total of 2113 cervical cancer cases and 2804 controls wereincluded. Results from this meta-analysis showed that significantly elevated cervical cancer risk was associatedwith the MTHFR T allele in the Asian population under conditions of two genetic comparison models (for TTvs. CC, OR = 1.37, 95%CI 1.00-1.87, P = 0.050; for TT vs. TC+CC: OR = 1.34, 95%CI 1.01-1.77, P = 0.039).However, there was no obvious association between the MTHFR C677T polymorphism and cervical cancer riskin the other populations. Conclusion: The MTHFR C677T polymorphism is associated with cervical cancer riskin Asians, while any possible link in the Caucasian population needs further studies.     

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.     

Relationship between methylenetetrahydrofolate reductase C677T and A1298C genotypes and haplotypes and prostate cancer risk and aggressiveness.

Previous reports indicate that polymorphisms in the MTHFR gene play a role in cancer development, but their potential impact on prostate cancer has not been well studied. Here, we evaluate the association between two MTHFR polymorphisms, C677T and A1298C, and prostate cancer risk and aggressiveness in a moderately large family-based case-control study (439 cases and 479 sibling controls). Among all study subjects, we observed no association between the C677T variant and prostate cancer but a slight positive association between the A1298C variant and risk of this disease [odds ratio (OR) 1.41, 95% confidence interval (CI) 0.96-2.06; P = 0.08]. When stratifying the study population by disease aggressiveness at diagnosis, the C677T variant was positively associated with risk among men with less advanced disease (OR 1.86, 95% CI 1.00-3.46; P = 0.05). In contrast, when looking at men with more advanced disease, the C677T variant was inversely associated with risk (OR 0.51, 95% CI 0.32-0.82; P = 0.01), whereas the A1298C variant was positively associated with risk (OR 1.79, 95% CI 1.06-3.02; P = 0.03). Furthermore, the 677T-1298A haplotype was positively associated with prostate cancer among men with less advanced disease (OR 1.84, 95% CI 1.07-3.16; P = 0.03) and inversely associated with risk of more advanced disease (OR 0.47, 95% CI 0.29-0.76; P = 0.002). Our findings suggest that 677T and 1298A, or another variant on their haplotype, may be associated with a reduced risk of progression to more advanced prostate cancer.     

The methylenetetrahydrofolate reductase (MTHFR) gene in colorectal cancer

Background and Aim: Folate deficiency predisposes to sporadic colorectal cancer (CRC). Methylenetetrahydrofolate reductase (MTHFR) is a critical folate-metabolising enzyme and a polymorphism at position 677 (C677T), is associated with reduced enzyme activity. We investigated whether this functional polymorphism modulates the risk of developing CRC. Methods: This was a retrospective case-control study, 136 unselected cases of sporadic CRC and 848 normal population controls were genotyped for the MTHFR C677T polymorphism. Tumor tissue was genotyped to assess loss of heterozygosity (LOH). Results: MTHFR CT heterozygotes had a significantly increased risk of developing CRC (53.7% of CRC cases vs 38.4% of controls), odds ratio 1.86 (95% CI 1.3–2.7, p<0.005). No increased cancer risk was observed in TT homozygotes. The MTHFR ‘T’ allele frequency was significantly higher in the cancer group (0.3713) as compared to controls (0.2900, p<0.008). LOH at the MTHFR locus was observed in 18% of informative cancers, with exclusive loss of the variant ‘T’ allele, in all cases. Conclusion: In this study of a homogenous northern European population, MTHFR CT heterozygotes had an almost two-fold increased risk of developing sporadic CRC. The exclusive pattern of MTHFR allele loss in cases of LOH, suggest that functional MTHFR activity within a tumor might play an important role in the survival and progression of a colonic neoplasm.     

Preponderance of methylenetetrahydrofolate reductase C677T homozygosity among leukemia patients intolerant to methotrexate.

BACKGROUND: Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, a common mutation of the gene encoding the enzyme that catalyzes reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a carbon donor in the metabolism of folate, determines a striking reduction in the enzyme activity in carriers of mutation at homozygous status. PATIENTS AND METHODS: We retrospectively analyzed the incidence of MTHFR C677T and the influence of genotype on methotrexate (MTX) toxicity in patients with acute leukemia undergoing maintenance chemotherapy. Seventy-eight patients were analyzed and 61 were evaluable for toxicity. MTX toxicity was assessed on bone marrow, liver and mucosae. RESULTS: The incidence of the C677T mutation was as expected in the general Italian population with 23.08% of patients being TT, 38.46% of patients CT and 38.46% of patients CC. The TT genotype was significantly associated with an increase of toxicity during MTX administration. No specific pattern of toxicity was detected, although in TT patients myelosuppression and liver toxicity were more pronounced. CONCLUSIONS: TT genotype may indicate a need to reduce the dose of MTX during prolonged administration. Considering the high prevalence of homozygous individuals in the Italian population, pretreatment screening may be worthwhile.