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

Association of Methylenetetrahydrofolate Reductase (MTHFR) Polymorphism with Osteosarcoma in a Mexican Population

The methylenetetrahydrofolate reductase (MTHFR) gene 677C➔T polymorphism is capable of altering folate metabolism and can modify certain neoplasia risk. Reports have suggested that folate can have an influence on bone development and so it is of interest to know if the MTHFR 677C➔T polymorphism is associated with the malignant transformation process of this tissue. The polymorphism was determined in 55 patients with osteosarcoma and in 180 healthy individuals. Compared with C/T+C/C genotypes, a 3.7-fold reduction in osteosarcoma probability is possible with the T/T genotype (OR 0.27, CI 95% 0.07-0.82). Undoubtedly, further studies, utilizing large samples and carried out on different populations, are necessary to confirm these results.

The combined effect of MTHFR C677T and A1298C polymorphisms on the risk of digestive system cancer among a hypertensive population

BACKGROUND AND PURPOSE

The enzyme methylenetetrahydrofolate reductase (MTHFR) plays a crucial role in directing folate species towards nucleotide synthesis or DNA methylation. The MTHFR polymorphisms C677T and A1298C have been linked to cancer susceptibility, but the evidence supporting this association has been equivocal. To investigate the individual and joint associations between MTHFR C677T, A1298C, and digestive system cancer in a Chinese hypertensive population, we conducted a population-based case-control study involving 751 digestive system cancer cases and one-to-one matched controls from the China H-type Hypertension Registry Study (CHHRS).

METHODS

We utilized the conditional logistic regression model to evaluate multivariate odds ratios (ORs) and 95% confidence intervals (CIs) of digestive system cancer.

RESULTS

The analysis revealed a significantly lower risk of digestive system cancer in individuals with the CT genotype (adjusted OR: 0.71; 95% CI 0.52, 0.97; P = 0.034) and TT genotype (adjusted OR: 0.57; 95% CI 0.40, 0.82; P = 0.003; P for trend = 0.003) compared to those with the 677CC genotype. Although A1298C did not show a measurable association with digestive system cancer risk, further stratification of 677CT genotype carriers by A1298C homozygotes (AA) and heterozygotes (AC) revealed a distinct trend within these subgroups.

CONCLUSION

These findings indicate a potential protective effect against digestive system cancer associated with the T allele of MTHFR C677T. Moreover, we observed that the presence of different combinations of MTHFR polymorphisms may contribute to varying susceptibilities to digestive system cancer.

Methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and gastric cancer susceptibility: an updated meta-analysis

Widely regarded as one of the most prevalent malignancies worldwide, gastric cancer (GC) is a common clinical condition of the digestive system. Reviewing 14 meta-analyses that evaluated the association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and GC risk, we observed inconsistent results, and the credibility of the significant correlation between the statistical results was ignored. With the aim of further exploring the association between MTHFR C677T and A1298C and the risk of GC, we searched electronic databases, pooling 43 relevant studies and calculating odds ratios (ORs) and corresponding 95% confidence intervals (CIs) for each of the five genetic models. Subgroup and regression analyses were performed to look for sources of heterogeneity and publication bias was assessed by funnel plots. To assess the plausibility of statistically significant associations, we used the FPRP test and the Venice criteria. Overall data analysis showed that MTHFR C677T polymorphism was significantly associated with GC risk, especially in Asians, while MTHFR A1298C polymorphism was not associated with GC risk. However, in subgroup analysis by hospital-based controls, we found that MTHFR A1298C might be a protective factor for GC. After credibility assessment, the statistical association between MTHFR C677T and GC susceptibility study was classified as 'less credible positive result', while the result of MTHFR A1298C was considered unreliable. In summary, the present study strongly suggests that MTHFR C677T and A1298C polymorphisms are not significantly associated with the GC risk.

Sex-Related Differences in Impact on Safety of Pharmacogenetic Profile for Colon Cancer Patients Treated with FOLFOX-4 or XELOX Adjuvant Chemotherapy

Polymorphisms contribute to inter-individual differences and show a promising predictive role for chemotherapy-related toxicity in colon cancer (CC). TOSCA is a multicentre, randomized, non-inferiority, phase III study conducted in high-risk stage II/stage III CC patients treated with 6 vs 3 months of FOLFOX-4 or XELOX adjuvant chemotherapy. During this post-hoc analysis, 218 women and 294 men were genotyped for 17 polymorphisms: TYMS (rs34743033, rs2853542, rs11280056), MTHFR (rs1801133, rs1801131), ERCC1 (rs11615), XRCC1 (rs25487), XRCC3 (rs861539), XPD (rs1799793, rs13181), GSTP1 (rs1695), GSTT1/GSTM1 (deletion +/−), ABCC1 (rs2074087), and ABCC2 (rs3740066, rs1885301, rs4148386). The aim was to assess the interaction between these polymorphisms and sex, on safety in terms of time to grade ≥3 haematological (TTH), grade ≥3 gastrointestinal (TTG) and grade ≥2 neurological (TTN) toxicity. Interactions were detected on TTH for rs1801133 and rs1799793, on TTG for rs13181 and on TTN for rs11615. Rs1799793 GA genotype (p = 0.006) and A allele (p = 0.009) shortened TTH in men. In women, the rs11615 CC genotype worsened TTN (co-dominant model p = 0.008, recessive model p = 0.003) and rs13181 G allele improved the TTG (p = 0.039). Differences between the two sexes in genotype distribution of rs1885301 (p = 0.020) and rs4148386 (p = 0.005) were found. We highlight that polymorphisms could be sex-specific biomarkers. These results, however, need to be confirmed in additional series.

Methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms in breast cancer: a Sardinian preliminary case-control study

Two common polymorphisms in the MTHFR gene, C677T and A1298C, are associated with reduced enzyme activity and may be associated with breast cancer susceptibility. We performed a case-control study to investigate the association between the two SNPs in the MTHFR gene and risk of breast cancer. In total, 58 breast cancer patients and 58 unaffected controls were enrolled in the study. Polymerase chain reaction/restriction fragment length polymorphism technique (PCR-RFLP) was conducted to determine the genotypes. No significant differences were found in the genotypes of the two polymorphisms of the MTHFR gene between cases and controls. The OR and 95% CI for the 677CC, 677CT and 677TT genotypes were 1.00, 0.95 (0.39-2.31) and 0.87 (0.27-2.80), respectively; those of the 1298AA, 1298AC and 1298CC genotypes were 1.00, 0.59 (0.26-1.36) and 0.78 (1.32-4.66) respectively. Furthermore, it has been shown in patients with breast cancer a risk of presenting with an aggressive biophenotype about twice or three times higher in the presence of the C677T and A1298C polymorphisms, respectively. Finally, the A1298Cpolymorphism is significantly associated with increased recurrence risk of lymph node-positive breast cancer. Our study has not shown a significant association between MTHFR gene polymorphisms and breast cancer risk. However, it highlighted the key-role played by the presence of mutant alleles for both polymorphisms in increasing the risk of developing more aggressive phenotypes; moreover, specifically in A1298C, it might also lead to a higher risk of developing lymph node metastasis.

Determining the association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and genomic DNA methylation level: A meta-analysis

BACKGROUND

The methylenetetrahydrofolate reductase (MTHFR) polymorphism is a risk factor for neural tube defects. C677T and A1298C MTHFR polymorphisms produce an enzyme with reduced folate-related one carbon metabolism, and this has been associated with aberrant methylation modifications in DNA and protein.

METHODS

A meta-analysis was conducted to assess the association between MTHFR C677T/A1298C genotypes and global genomic methylation.

RESULTS

Eleven studies met the inclusion criteria. Of these, 10 were performed on C677T MTHFR genotypes and 6 were performed on A1298C MTHFR genotypes. Our results did not indicate any correlation between global methylation and MTHFR A1298C, C677T polymorphisms.

CONCLUSION

The results of our study provide evidence to assess the global methylation modification alterations of MTHFR polymorphisms among individuals. However, our data did not found any conceivable proof supporting the hypothesis that common variant of MTHFR A1298C, C677T contributes to methylation modification. Birth Defects Research (Part A) 106:667-674, 2016. © 2016 Wiley Periodicals, Inc.

Evaluation of an Association of Blood Homocysteine Levels With Gastric Cancer Risk From 27 Case-Control Studies

High blood homocysteine levels may risk gastric cancer. However, observational studies have been plagued by chance, bias, confounding, or reverse causality. In this study, we assessed the relationship between blood homocysteine levels and gastric cancer by using a Mendelian randomization method, which is independent of nongenetic confounding.We took 2 steps to perform Mendelian randomization analysis. First, we evaluated the methylenetetrahydrofolate reductase (MTHFR) C677T association with gastric cancer by a meta-analysis of case-control studies including 7566 patients with gastric cancer and 10 640 control subjects from 27 Case-Control studies. Second, MTHFR C677T polymorphism, which affects the blood homocysteine levels, was used as an instrumental variable to calculate the risk and estimate the association of gastric cancer with this single nucleotide polymorphism (SNP). We obtained an estimate to the association of blood total homocysteine levels with this SNP from a meta-analysis of Genome-Wide Association Studies (GWAS), which comprises a total of 44 147 individuals.In our Mendelian randomization analysis, we demonstrated a significant effect of the blood homocysteine levels on gastric cancer risk, representing an OR of 2.56 (95% CI = 2.41-2.72; P = 5.0×10) for gastric cancer per 1-SD increase in the natural log-transformed blood total homocysteine levels.We proved that there is a causal relationship between blood total homocysteine and risk of gastric cancer, and this study will add insight into the treatment and pathology research of gastric cancer.

Lack of association between MTHFR C677T polymorphism and breast cancer risk in Ahvaz, west south-Iran

Background:

Association between C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR), a key enzyme involved in folate metabolism and DNA methylation, and breast cancer risk are inconsistent. We investigated in a case-control study, possible effect of the common MTHFR C677T polymorphism on breast cancer risk in a sample of Iranian patients.

Materials and Methods:

The study subjects comprised of 123 breast cancer cases and 110 cancer-free control, who were matched for age and body mass index (BMI). C677T genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay. Lipid profile was measured in all subjects by standard method.

Results:

The genotypes distributions (CC, CT, and TT) were 55.3, 39, and 5.7% in breast cancer cases and 51.8, 44.5, and 3.6% in controls. Chi square analysis revealed that there was no significant association between breast cancer risk and MTHFR genotypes and alleles. Additionally, no significant association was observed between C677T genotypes and biochemistry parameters. A multinomial logistic regression model with MTHFR genotypes, lipid profiles, BMI and age as covariates revealed that there is no significant association between MTHFR genotypes and risk of breast cancer, but higher values of LDL and HDL significantly increase risk of breast cancer.

Conclusions:

Our findings do not support the hypothesis that genetic variation in the MTHFR C677T polymorphism is implicated in the breast cancer risk in a sample of Iranian patients.

Association between the MTHFR C677T polymorphism and gastric cancer susceptibility: A meta-analysis of 5,757 cases and 8,501 controls

Current data regarding the association between the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and the risk of developing gastric cancer are insufficient to draw definite conclusions. Therefore, the present meta-analysis was conducted to achieve a more precise estimation of the association. MEDLINE, EMBASE and Wanfang database searches resulted in the identification of 28 eligible studies describing 5,757 cases and 8,501 controls. The strength of the association between the MTHFR C677T polymorphism and gastric cancer risk were evaluated using crude odds ratios (ORs), with 95% confidence intervals (CIs). The pooled ORs were determined using homozygous (TT vs. CC), heterozygous (CT vs. CC), dominant (TT+CT vs. CC) and recessive (TT vs. CC+CT) models. When all studies were pooled into the meta-analysis, significant associations were identified between the MTHFR C677T polymorphism and the risk of gastric cancer (homozygous model: OR, 1.39; 95% CI, 1.20-1.62; heterozygous model: OR, 1.18; 95% CI, 1.05-1.32; dominant model: OR, 1.23; 95% CI, 1.10-1.38; recessive model: OR, 1.26; 95% CI, 1.12-1.42). Stratification of the data by ethnicity identified a statistically significantly elevated risk of gastric cancer in Asian MTHFR C677T polymorphism populations (homozygous model: OR, 1.64; 95% CI, 1.43-1.90; heterozygous model: OR, 1.30; 95% CI, 1.16-1.45; dominant model: OR, 1.39; 95% CI, 1.25-1.54; recessive model: OR, 1.41; 95% CI, 1.25-1.51), but not in Caucasian populations (homozygous model: OR, 1.15; 95% CI, 0.89-1.48; heterozygous model: OR, 1.03; 95% CI, 0.84-1.25; dominant model: OR, 1.05; 95% CI, 0.86-1.28; recessive model: OR, 1.09; 95% CI, 0.91-1.31). Following adjustment for heterogeneity, the current meta-analysis demonstrated that the MTHFR C677T polymorphism was not associated with the risk of gastric cancer in Caucasian individuals. Furthermore, no evidence of publication bias was observed. Thus, the current meta-analysis indicates that the MTHFR C677T allele may be a low-penetrant risk factor for the development of gastric cancer in Asian populations.

Methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and gastric cancer susceptibility

AIM: To identify the association between methylenetetrahydrofolate reductase (MTHFR) polymorphisms and gastric cancer (GC) susceptibility.

METHODS: Systematic searches were performed on the electronic databases PubMed, ISI, Web of knowledge, CNKI and Wanfang, as well as manual searching of the references of the identified articles. A total of 26 papers were included in this meta-analysis. Overall and subgroup analyses were performed. Odds ratio (OR) and 95%CI were used to evaluate the associations between MTHFR polymorphisms and GC risk. The I² statistics were used to evaluate between-study heterogeneity. Sensitivity analysis was also performed.

RESULTS: Increased risk was found for the MTHFR C677T polymorphism under four genetic models (TT + CT vs CC: OR = 1.23, P = 0.002; T vs C: OR = 1.15, P = 0.001; TT vs CC: OR = 1.37, P = 0.0005; TT vs CT + CC: OR = 1.17, P = 0.0008). Subgroup analysis by ethnicity suggested that C677T polymorphism conferred a risk of GC in eastern but not in western populations. Stratification by tumor site showed an association between the C677T polymorphism and gastric cardia cancer and non-cardia GC in the worldwide population and in eastern populations. Regardless of comparisons with controls or diffuse-type GC, a positive association was found for the C677T polymorphism and an increased risk of intestinal-type GC in the whole population and in western populations. With regard to the A1298C polymorphism, we found that genotype CC was significantly decreased and conferred protection against GC in eastern populations (CC vs AA: OR = 0.44, P = 0.03; CC vs AC + AA: OR = 0.46, P = 0.04).

CONCLUSION: MTHFR C677T polymorphism is a risk factor for GC, and the A1298C polymorphism may be a protective factor against GC in eastern populations.

Gene-diet interactions in gastric cancer risk: A systematic review

AIM: To conduct a systematic review of the published epidemiological studies investigating the association of the interactions between gene variants and dietary intake with gastric cancer risk.

METHODS: A literature search was conducted in PubMed, EMBASE, and MEDLINE for articles published between January 2000 and July 2013, and 38 studies were identified. Previous studies included various dietary factors (e.g., fruits and vegetables, soybean products, salt, meat, and alcohol) and genetic variants that are involved in various metabolic pathways.

RESULTS: Studies suggest that individuals who carry high-risk genetic variants and demonstrate particular dietary habits may have an increased risk of gastric cancer compared with those who do not carry high-risk genetic variants. Distinctive dietary patterns and variations in the frequency of genetic variants may explain the higher incidence of gastric cancer in a particular region. However, most previous studies have limitations, such as a small sample size and a retrospective case-control design. In addition, past studies have been unable to elucidate the specific mechanism in gene-diet interaction associated with gastric carcinogenesis.

CONCLUSION: Additional large prospective epidemiological and experimental studies are required to identify the gene-diet metabolic pathways related to gastric cancer susceptibility.

Folate intake and the risk of oral cavity and pharyngeal cancer: a pooled analysis within the International Head and Neck Cancer Epidemiology Consortium

There are suggestions of an inverse association between folate intake and serum folate levels and the risk of oral cavity and pharyngeal cancers (OPCs), but most studies are limited in sample size, with only few reporting information on the source of dietary folate. Our study aims to investigate the association between folate intake and the risk of OPC within the International Head and Neck Cancer Epidemiology (INHANCE) Consortium. We analyzed pooled individual-level data from ten case-control studies participating in the INHANCE consortium, including 5,127 cases and 13,249 controls. Odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were estimated for the associations between total folate intake (natural, fortification and supplementation) and natural folate only, and OPC risk. We found an inverse association between total folate intake and overall OPC risk (the adjusted OR for the highest vs. the lowest quintile was 0.65, 95% CI: 0.43-0.99), with a stronger association for oral cavity (OR = 0.57, 95% CI: 0.43-0.75). A similar inverse association, though somewhat weaker, was observed for folate intake from natural sources only in oral cavity cancer (OR = 0.64, 95% CI: 0.45-0.91). The highest OPC risk was observed in heavy alcohol drinkers with low folate intake as compared to never/light drinkers with high folate (OR = 4.05, 95% CI: 3.43-4.79); the attributable proportion (AP) owing to interaction was 11.1% (95% CI: 1.4-20.8%). Lastly, we reported an OR of 2.73 (95% CI:2.34-3.19) for those ever tobacco users with low folate intake, compared with nevere tobacco users and high folate intake (AP of interaction =10.6%, 95% CI: 0.41-20.8%). Our project of a large pool of case-control studies supports a protective effect of total folate intake on OPC risk.

MTHFR C677T polymorphism contributes to the risk for gastric cancer

Methylenetetrahydrofolate reductase (MTHFR) has been demonstrated to be involved in carcinogenesis. Increasing individual studies have investigated the role of MTHFR C677T polymorphism in gastric cancer pathogenesis, but with inconsistent findings. The aim of this study was to clarify the potential association of the MTHFR C677T polymorphism with gastric cancer risk by pooling all available data from published case-control studies. We searched the PubMed, Embase, Web of Science, and Wanfang databases for all relevant publications to date. The pooled odds ratio (OR) with corresponding 95 % confidence interval (95% CI) was calculated. Stratified analysis and sensitivity analysis were also carried out to estimate the strength of this association. A total of 25 case-control studies with 6,572 cases and 9,584 controls were retrieved. Overall, the ORs under five contrast models indicated that the MTHFR C677T variant was positively associated with gastric cancer risk (ORT vs. C = 1.21, 95% CI 1.10–1.34, P(OR) < 0.001; OR(TT vs. CC) = 1.47, 95% CI 1.22–1.76, P(OR) < 0.001; OR(TC vs. CC) = 1.20, 95% CI 1.03-1.40, P(OR) = 0.022; OR(TT + TC vs. CC) = 1.27, 95% CI 1.10-1.47, P(OR) = 0.001; OR(TT vs. CC + TC) = 1.29, 95% CI 1.15-1.46, P(OR) < 0.001). Stratified analyses according to ethnicity and source of controls further confirmed the significant correlations. The current meta-analysis provides strong evidence that the MTHFR C677T polymorphism may be a risk factor for gastric cancer among Asians and Caucasians.

The methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and tumor risk: evidence from 134 case-control studies

Methylenetetrahydrofolate reductase (MTHFR) is an important enzyme involved in folate metabolism, which is essential for DNA synthesis and methylation. Genetic variations in the MTHFR gene seem to contribute to a decreased activity of MTHFR, ultimately confer increased susceptibility to cancer. As the most extensively studied polymorphism, MTHFR C677T polymorphism was shown to contribute to cancer susceptibility but the results were inconsistent. The authors performed a meta-analysis including 134 studies (46,207 cases and 69,160 controls) to address the issue. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to assess the association. Overall, a significant elevated risk of cancer was associated with the MTHFR C677T polymorphism in T-allele versus C-allele comparison (OR = 1.06, 95% CI 1.02-1.11, P(heterogeneity) < 0.001), homozygote model (OR = 1.08, 95% CI 1.01-1.17, P(heterogeneity) < 0.001) and dominant model (OR = 1.05, 95% CI 1.00-1.10, P(heterogeneity) < 0.001). In the stratified analyses, significantly increased cancer risks were indicated among Asians in all genetic models except for heterozygote model. Further analysis revealed that C677T was significantly associated with an increased risk of esophageal and stomach cancer. This meta-analysis supports an association between the MTHFR C677T polymorphism and increased risk of esophageal and stomach cancer, especially among Asians. Additionally, more high-quality studies and that the covariates responsible for heterogeneity should be controlled to obtain a more conclusive response about the function of MTHFR C677T in cancer.

The MTHFR C677T polymorphism and global DNA methylation in oral epithelial cells

DNA methylation is mediated by DNA methyltransferases (DNMTs) that add a methyl group to the 5′-carbon of cytosine. The enzyme methylenetetrahydrofolate reductase (MTHFR) catalyzes the reduction of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate in the rate-limiting step of the cycle involving the methyl donor S-adenosyl-L-methionine (SAM). The MTHFR C677T polymorphism results in a thermolabile enzyme with reduced activity that is predicted to influence the DNA methylation status. In this study, we investigated the impact of the MTHFR C677T polymorphism on the global DNA methylation of oral epithelial cells obtained from 54 healthy subjects. There were no significant differences in global DNA methylation among the MTHFR CC, CT and TT genotypes (p = 0.75; Kruskal-Wallis test).

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.

Pharmacogenomic assessment of outcomes of pemetrexed-treated patients with adenocarcinoma of the lung

PURPOSE

The main objective of this study was to evaluate the association between polymorphisms of the target genes of pemetrexed and clinical outcomes in non-small cell lung cancer (NSCLC) patients treated with pemetrexed.

MATERIALS AND METHODS

We assessed polymorphisms at 8 sites in 4 genes [thymidylate synthase (TS), dihydrofolate reductase (DHFR; 1610, 680, 317, intron 1), methylenetetrahydrofolate reductase (MTHFR; 677, 1298), glycinamide ribonucleotide formyl transferase (GARFT; 2255)] associated with pemetrexed metabolism using polymerase chain reaction, gene scanning, and restriction fragment length polymorphism analysis in 90 patients with adenocarcinoma of the lung.

RESULTS

Survival was significantly longer with pemetrexed in patients with TS 3RGCC/3RGCC or 3RGGC/3RGGC compared with the other groups (PFS; 5.2 months vs. 3.7 months, p=0.03: OS; 31.8 months vs. 18.5 months, p=0.001). Patients with DHFR 680CC experienced fatigue more frequently (50% vs. 8.6%, p=0.008). Polymorphisms of MTHFR and GARFT were not significantly associated with clinical outcomes of pemetrexed.

CONCLUSION

The TS genotype was associated with survival and one DHFR polymorphism was associated with fatigue in NSCLC patients treated with pemetrexed. Further large prospective studies are required to identify other biomarkers that affect patients being treated with pemetrexed for adenocarcinoma of the lung.

A literature review of MTHFR (C677T and A1298C polymorphisms) and cancer risk

5,10-Methlenetetrahydrofolate reductase (MTHFR) is one of the most important enzymes for folate metabolism. This enzyme is mapped on chromosome 1, which is located at the end of the short arm (1p36.3). The C677T and A1298C are MTHFR polymorphisms that decrease in vitro MTHFR enzyme activity. Folate metabolism plays a key role in cell metabolism. These reactions are associated with purine-pyrimidine synthesis: DNA, RNA, and protein methylation. Polymorphism is also a factor in biodiversity, and be affected by ethnic heritage and geographic locale. In the case of unknown outcomes, not only should all geographical regions be investigated to ascertain biodiversity, but all populations as well to fully understand the variations in the effect. PUBMED was searched from January 2006 to December 2011 to develop an investigatory pursuit strategy. MTHFR, cancer, C677T, A1298C, and polymorphisms were key words used to focus the search. The literature review included all published relevant cancer types and MTHFR polymorphisms for that 5 years period. All selected polymorphisms data for cancer types was listed in tables for easy access and retrieval.

Molecular logic underlying chromosomal translocations, random or non-random?

Chromosomal translocations serve as essential diagnostic markers and therapeutic targets for leukemia, lymphoma, and many types of solid tumors. Understanding the mechanisms of chromosomal translocation generation has remained a central biological question for decades. Rather than representing a random event, recent studies indicate that chromosomal translocation is a non-random event in a spatially regulated, site-specific, and signal-driven manner, reflecting actions involved in transcriptional activation, epigenetic regulation, three-dimensional nuclear architecture, and DNA damage-repair. In this review, we will focus on the progression toward understanding the molecular logic underlying chromosomal translocation events and implications of new strategies for preventing chromosomal translocations.

DNA methylation in peripheral blood measured by LUMA is associated with breast cancer in a population-based study

Our purpose was to identify epigenetic markers of breast cancer risk, which can be reliably measured in peripheral blood and are amenable for large population screening. We used 2 independent assays, luminometric methylation assay (LUMA) and long interspersed elements-1 (LINE-1) to measure "global methylation content" in peripheral blood DNA from a well-characterized population-based case-control study. We examined associations between methylation levels and breast cancer risk among 1055 cases and 1101 controls and potential influences of 1-carbon metabolism on global methylation. Compared with women in the lowest quintile of LUMA methylation, those in the highest quintile had a 2.41-fold increased risk of breast cancer (95% confidence interval: 1.83-3.16; P, trend<0.0001). The association did not vary by other key tumor characteristics and lifestyle risk factors. Consistent with LUMA findings, genome-wide methylation profiling of a subset of samples revealed greater promoter hypermethylation in breast cancer case participants (P=0.04); higher LUMA was associated with higher promoter methylation in the controls (P=0.05). LUMA levels were also associated with functional sodium nitroprusside in key 1-carbon metabolizing genes, MTHFR C677T (P=0.001) and MTRR A66G (P=0.018). LINE-1 methylation was associated with neither breast cancer risk nor 1-carbon metabolism. Our results show that global promoter hypermethylation measured in peripheral blood was associated with breast cancer risk.

Host genetic variants in the IGF binding protein-3 impact on survival of patients with advanced gastric cancer treated with palliative chemotherapy

AIM

IGF binding protein-3 (IGFBP-3) displays growth inhibitory/proapoptotic action and counteracts the IGF-1 tumor-promoting effects by downregulating its bioavailability. We investigated whether IGFBP-3 SNPs determining high IGFBP-3 circulating levels are associated with improved survival of patients with advanced gastric cancer treated with palliative chemotherapy.

MATERIALS & METHODS

A total of 185 patients undergoing combination chemotherapy for relapsed/metastatic disease were considered eligible for the present clinical investigation. Four functional IGFBP-3 SNPs (rs3110697, rs2854746, rs2864744 and rs2960436) were studied for association with overall survival (OS).

RESULTS

In the multivariate model including SNPs and clinicopathologic features, the rs285744 A allele and the rs2960436 A allele showed favorable association with survival. The hazard ratios for rs285744 C/A and A/A genotypes were 0.38 (95% CI: 0.18-0.66) and 0.20 (95% CI: 0.09-0.39), respectively. The hazard ratios for rs2960436 G/A and A/A genotypes were 0.41 (95% CI: 0.25-0.68) and 0.35 (95% CI: 0.16-0.58), respectively. Bonferroni-corrected p-values for the rs285744 A/A genotype and the rs2960436 A/A genotype were 0.012 and 0.024, respectively. There was linkage disequilibrium between the four variants and there were four common haplotypes (>5% estimated frequency). The most common haplotype (GCAA) included all alleles causing IGFBP-3 upregulation and their carriers demonstrated the best outcome in the log-rank comparison of survival curves.

CONCLUSION

Genetic regulation of the IGFBP-3 impacts on survival of patients with advanced gastric cancer. This finding deserves additional studies because of its prognostic and therapeutic implications.

DNA damage and L1 retrotransposition

Barbara McClintock was the first to suggest that transposons are a source of genome instability and that genotoxic stress assisted in their mobilization. The generation of double-stranded DNA breaks (DSBs) is a severe form of genotoxic stress that threatens the integrity of the genome, activates cell cycle checkpoints, and, in some cases, causes cell death. Applying McClintock's stress hypothesis to humans, are L1 retrotransposons, the most active autonomous mobile elements in the modern day human genome, mobilized by DSBs? Here, evidence that transposable elements, particularly retrotransposons, are mobilized by genotoxic stress is reviewed. In the setting of DSB formation, L1 mobility may be affected by changes in the substrate for L1 integration, the DNA repair machinery, or the L1 element itself. The review concludes with a discussion of the potential consequences of L1 mobilization in the setting of genotoxic stress.

Methylenetetrahydrofolate reductase C677T polymorphism in patients with gastric and colorectal cancer in a Korean population

Background

This study was designed to investigate an association between the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and the risk of gastric and colorectal cancer in the Korean population.

Methods

We conducted a population-based large-scale case-control study involving 2,213 patients with newly diagnosed gastric cancer, 1,829 patients with newly diagnosed colorectal cancer, and 1,700 healthy controls. Genotyping was performed with peripheral blood DNA for MTHFR C677T polymorphisms. The statistical significance was estimated by logistic regression analysis.

Results

The MTHFR C677T frequencies of CC, CT, and TT genotypes were 35.2%, 47.5%, and 17.3% among stomach cancer, 34%, 50.5%, and 15.5% in colorectal cancer, and 31.8%, 50.7%, and 17.5% in the controls, respectively. The MTHFR 677TT genotype showed a weak opposite association with colorectal cancer compared to the homozygous CC genotype [adjusted age and sex odds ratio (OR) = 0.792, 95% confidence interval (CI) = 0.638-0.984, P = 0.035]. Subjects with the MTHFR 677CT showed a significantly reduced risk of gastric cancer compared whose with the 677CC genotype (age- and sex-adjusted OR = 0.810; 95% CI = 0.696-0.942, P = 0.006). We also observed no significant interactions between the MTHFR C677T polymorphism and smoking or drinking in the risk of gastric and colorectal cancer.

Conclusions

The T allele was found to provide a weak protective association with gastric cancer and colorectal cancer.

Methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and gastric cancer: a meta-analysis

BACKGROUND AND AIMS

Case/control studies that investigated the association between gastric cancer and the MTHFR C677T and A1298C polymorphisms so far have provided controversial results. To clarify the effect of MTHFR polymorphisms on the risk of gastric cancer, a meta-analysis was performed.

METHODS

We performed a computerized search of the PubMed database for relevant reports before September 2009. No language restrictions were added. The associated literature was acquired through a deliberate retrieval strategy and selected based on the established inclusion criteria for publications.

RESULTS

The studies provided 4070/6462 cases/controls for C677T and 1923/3561 cases/controls for A1298C. There was significant heterogeneity (p = 0.015, I(2) = 44.0%) among the 22 studies, and the RE model showed that the C677T allele T was associated with a 17.3% increased risk of gastric cancer compared with the allele C (RE OR = 1.173 [1.051-1.274]). Results from the subgroup analysis showed an increased risk in Asians (fixed-effect, FE OR 1.277 [1.179-1.382]), but not in Caucasians (random-effect, RE OR 1.194 [0.866-1.646]). The contrast of homozygotes (TT vs. CC) produced significant results in Asians (FE OR 1.611 [1.366-1.901]), whereas, in Caucasians, it was not significant (RE OR 1.385 [0.754-2.544]). In regard to the A1298C polymorphism, there was no heterogeneity among the 11 studies comparing the C vs. the A allele (p = 0.352, I(2) = 9.7%), but no significant association was detected.

CONCLUSIONS

The evidence from our meta-analysis supports that TT genotype of MTHFR C677T polymorphism contributes to susceptibility to gastric cancer, but no significant association was detected for CC genotype of MTHFR A1298C.

Implications of LINE1 methylation for bladder cancer risk in women

PURPOSE

Epigenetic alterations including changes to cellular DNA methylation levels contribute to carcinogenesis and may serve as powerful biomarkers of the disease. This investigation sought to determine whether hypomethylation at the long interspersed nuclear elements (LINE1), reflective of the level of global DNA methylation, in peripheral blood-derived DNA is associated with increased risk of bladder cancer.

EXPERIMENTAL DESIGN

LINE1 methylation was measured from blood-derived DNA obtained from participants of a population-based incident case-control study of bladder cancer in New Hampshire. Bisulfite-modified DNA was pyrosequenced to determine LINE1 methylation status; a total of 285 cases and 465 controls were evaluated for methylation.

RESULTS

Being in the lowest LINE1 methylation decile was associated with a 1.8-fold increased risk of bladder cancer [95% confidence interval (95% CI), 1.12-2.90] in models controlling for gender, age, and smoking, and the association was stronger in women than in men (odds ratio, 2.48; 95% CI, 1.19-5.17 in women; and odds ratio, 1.47; 95% CI, 0.79-2.74 in men). Among controls, women were more likely to have lower LINE1 methylation than men (P = 0.04), and levels of arsenic in the 90th percentile were associated with reduced LINE1 methylation (P = 0.04).

CONCLUSIONS

LINE1 hypomethylation may be an important biomarker of bladder cancer risk, especially among women.

MTHFR polymorphisms in gastric cancer and in first-degree relatives of patients with gastric cancer

Two common mutations, 677 C→T and a1298 A→C, in the methylenetetrahydrofolate reductase gene (MTHFR) reduce the activity of MTHFR and folate metabolism. Familial aggregation in a variable but significant proportion of gastric cancer (GC) cases suggests the importance of genetic predisposition in determining risk. In this study, we evaluate MTHFR polymorphisms in 57 patients with a diagnosis of GC, in 37 with a history of GC in first-degree relatives (GC-relatives), and in 454 blood donors. Helicobacter pylori (HP) infection was also determined. An increased risk was found for 677TT in GC patients with respect to blood donors (odds ratio (OR) = 1.98), and statistical significance was sustained when we compared sex–age-matched GC patients and donors (OR = 2.37). The 677TT genotype association with GC was found in women (OR = 3.10), while a reduction in the 667C allele frequency was present in both the sex. No statistically significant association was detected when 677–1298 genotype was stratified by sex and age. Men of GC-relatives showed a higher 1298C allele frequency than donors (OR = 4.38). Between GC and GC-relatives, HP infection frequency was similar. In conclusion, overall findings support the hypothesis that folate plays a role in GC risk. GC-relatives evidence a similar 677TT frequency to that found in the general population.

Genetic factors associated with intestinal metaplasia in a high risk Singapore-Chinese population: a cohort study

Background

Intestinal metaplasia (IM) is an important precursor lesion in the development of gastric cancer (GC). The aim of this study was to investigate genetic factors previously linked to GC risk for their possible association with IM. A total of 18 polymorphisms in 14 candidate genes were evaluated in a Singapore-Chinese population at high risk of developing GC.

Methods

Genotype frequencies were compared between individuals presenting with (n = 128) or without (n = 246) IM by both univariate and multivariate analysis.

Results

Carriers of the NQO1 609 T allele showed an association with IM in individuals who were seropositive for Helicobacter pylori (HP+; OR = 2.61, 95%CI: 1.18-5.80, P = .018). The IL-10 819 C allele was also associated with IM in HP+ individuals (OR = 2.32, 95%CI: 1.21-4.43, P = 0.011), while the PTPN11 A allele was associated with IM in HP- individuals (OR = 2.51, 95%CI: 1.16-5.40, P = 0.019), but showed an inverse association in HP+ subjects (OR = 0.46, 95%CI: 0.21-0.99, P = 0.048).

Conclusion

Polymorphisms in NQO1, IL-10 and PTPN11, in combination with HP status, could be used to identify individuals who are more likely to develop IM and therefore GC.

Mathematical modeling of folate metabolism: predicted effects of genetic polymorphisms on mechanisms and biomarkers relevant to carcinogenesis

Low-folate status and genetic polymorphisms in folate metabolism have been linked to several cancers. Possible biological mechanisms for this association include effects on purine and thymidine synthesis, DNA methylation, or homocysteine concentrations. The influence of genetic variation in folate metabolism on these putative mechanisms or biomarkers of cancer risk has been largely unexplored. We used a mathematical model that simulates folate metabolism biochemistry to predict (a) the effects of polymorphisms with defined effects on enzyme function (MTHFR and TS) and (b) the effects of potential, as-of-yet-unidentified polymorphisms in a comprehensive set of folate-metabolizing enzymes on biomarkers and mechanisms related to cancer risk. The model suggests that there is substantial robustness in the pathway. Our predictions were consistent with measured effects of known polymorphisms in MTHFR and TS on biomarkers. Polymorphisms that alter enzyme function of FTD, FTS, and MTCH are expected to affect purine synthesis, FTS more so under a low-folate status. In addition, MTCH polymorphisms are predicted to influence thymidine synthesis. Polymorphisms in methyltransferases should affect both methylation rates and thymidylate synthesis. Combinations of polymorphisms in MTHFR, TS, and SHMT are expected to affect nucleotide synthesis in a nonlinear fashion. These investigations provide information on effects of genetic polymorphisms on biomarkers, including those that cannot be measured well, and highlight robustness and sensitivity in this complex biological system with regard to genetic variability. Although the proportional changes in biomarkers of risk with individual polymorphisms are frequently small, they may be quite relevant if present over an individual's lifetime.

Methylenetetrahydrofolate reductase polymorphisms and susceptibility to gastric cancer in Chinese populations: a meta-analysis

Genetic polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene are thought to have significant effects on folate metabolism and, thus, on cancer risk, but the reported results are not always consistent. In this meta-analysis including 2165 patients and 3279 controls, we assessed reported studies of associations between polymorphisms of MTHFR and susceptibility to gastric cancer in Chinese populations. An increased risk was found for MTHFR C677T in the meta-analysis [odds ratio (OR): 1.42; 95% confidence interval (CI): 1.24-1.62]. No association resulted for MTHFR A1298C (OR: 0.95; 95% CI: 0.78-1.17). Results from the subgroup analyses showed an increased risk for individuals with low (OR: 1.50; 95% CI: 1.18-1.91) versus high (OR: 1.21; 95% CI: 0.98-1.51) folate levels. The sensitivity analysis and publication bias diagnostics confirmed the reliability and stability of this meta-analysis. Overall, these findings support the hypothesis that folate plays a role in gastric carcinogenesis. Regarding cardia or noncardia gastric cancer, more studies are required for definite conclusions, as the number of studies is relatively small.

MTHFR C677T polymorphism and risk of HCC in patients with liver cirrhosis: role of male gender and alcohol consumption

BACKGROUND

A single nucleotide polymorphism (SNP) C677T in the methylenetetrahydrofolate reductase (MTHFR) gene has been identified. The TT or CT genotypes show a marked reduction of the enzyme activity; this causes higher homocysteine levels and alterations of folate metabolism. Folate metabolism is essential for DNA synthesis and methylation, crucial steps in carcinogenesis. In this paper, we investigated whether the MTHFR C677T SNP could influence the occurrence of hepatocellular carcinoma (HCC) in a cohort of patients transplanted for end stage liver disease of different etiologies.

METHODS

Two hundred and twelve consecutive patients who underwent liver transplantation for end stage liver disease due to hepatitis B or C, alcoholic liver disease, and other causes were studied. Two hundred and thirty-six blood donors served as controls. Focal hepatic lesions were searched in the sectioned explanted livers. The presence of the MTHFR C677T SNP was determined via polymerase chain reaction amplification.

RESULTS

Among the 65 patients with HCC, 22 had the CC genotype, 30 the CT, and 13 the TT genotype. Only in patients with alcoholic liver disease was a significant association detected between the TT genotype and the presence of liver cancer (6/17 vs. 5/46, p < 0.05). At stepwise logistic regression analysis the independent selected predictors of HCC were found: age at transplantation >55 years (p < 0.001) and the association among male gender, alcoholic liver disease, and MTHFR TT genotype (p = 0.002).

CONCLUSIONS

The present study suggests that male TT carriers with alcoholic cirrhosis bear an increased risk of developing HCC.

Review and pooled analysis of studies on MTHFR C677T polymorphism and esophageal cancer

Esophageal cancer has been associated with tobacco and alcohol consumption, gastric reflux, exposure to nitrosamines from food or other environmental sources, and diets lacking folate. Susceptibility to esophageal cancer may be modified by functional polymorphisms in genes along the folate metabolic pathway, such as methylenetetrahydrofolate reductase (MTHFR). The C677T polymorphism is the most common functional variant, leading to a reduction in enzyme activity. We report a pooled analysis of 5 studies on the association of MTHFR C677T polymorphism and esophageal cancer, including 725 cases and 1531 controls. A significant association between the MTHFR 677 TT genotype and esophageal cancer was observed (OR=2.63, 95% CI: 1.75-3.94), although there was significant heterogeneity between studies. A sensitivity analysis excluded one study; the association between TT genotype and esophageal cancer was still present, although of reduced magnitude (OR=1.57, 95% CI: 0.96-2.56). A significant interaction between smoking and TT genotype on esophageal cancer risk was observed, while no interaction was observed between alcohol consumption and genotype.

The association of gastric cancer risk with plasma folate, cobalamin, and methylenetetrahydrofolate reductase polymorphisms in the European Prospective Investigation into Cancer and Nutrition

Previous studies have shown inconsistent associations of folate intake and polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene with gastric cancer risk. Our nested case-control study within the European Prospective Investigation into Cancer and Nutrition cohort is the first prospective study of blood folate levels and gastric cancer. Gastric cancer cases (n=247) and controls (n=631) were matched for study center, age, sex, and time of blood donation. Two common single nucleotide polymorphisms of the MTHFR gene were determined, as were plasma concentrations of folate, cobalamin (vitamin B12), total homocysteine, and methylmalonic acid (cobalamin deficiency marker) in prediagnostic plasma. Risk measures were calculated with conditional logistic regression. Although no relations were observed between plasma folate or total homocysteine concentrations and gastric cancer, we observed a trend toward lower risk of gastric cancer with increasing cobalamin concentrations (odds ratio, 0.79 per SD increase in cobalamin; P=0.01). Further analyses showed that the inverse association between cobalamin and gastric cancer was confined to cancer cases with low pepsinogen A levels (marker of severe chronic atrophic gastritis) at the time of blood sampling. The 677 C-->T MTHFR polymorphism was not associated with gastric cancer, but we observed an increased risk with the variant genotype of the 1298 A-->C polymorphism (odds ratio, 1.47 for CC versus AA; P=0.04). In conclusion, we found no evidence of a role of folate in gastric cancer etiology. However, we observed increased gastric cancer risk at low cobalamin levels that was most likely due to compromised cobalamin status in atrophic gastritis preceding gastric cancer.

No association between global leukocyte DNA methylation and homocysteine levels in schizophrenia patients

Meta-analysis recently suggested that a 5 muM increase in homocysteine is associated with a 70% higher risk for schizophrenia. Elevated homocysteine is reported to alter macromolecule methylation. We studied whether elevated plasma homocysteine levels in schizophrenia are associated with altered leukocyte global DNA methylation. DNA was extracted from peripheral blood leukocytes of 28 schizophrenia patients vs. 26 matched healthy controls. Percent of global genome DNA methylation was measured using the cytosine-extension method. Homocysteine levels were higher in schizophrenia patients than in controls. No difference in global DNA methylation between schizophrenia patients and control subjects was found (74.0%+/-14.8 vs. 69.4+/-22.0, p=0.31). A significant interaction between diagnosis and smoking on DNA methylation was obtained (F=6.8, df=1,47, p=0.032). Although leukocytes may be a useful cell model to evaluate epigenetic changes such as global DNA methylation in brain, future studies should compare global DNA methylation in peripheral tissue vs. brain in laboratory animals.

Methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and susceptibility to gastric adenocarcinoma in an Italian population

Methylenetetrahydrofolate reductase (MTHFR) plays a central role in the metabolism of folate, which provides a methyl donor for DNA methylation and deoxynucleoside synthesis. We performed a case-control study to explore the relationship between two common MTHFR polymorphisms (C677T and A1298C), their combination and interaction with environmental exposures, on gastric adenocarcinoma susceptibility and progression in an Italian population. One hundred and two cases and 254 hospital controls, matched by age and gender, were enrolled. Individuals carrying the MTHFR 677T allele showed an increased risk of gastric cancer (odds ratio (OR) 1.62, 95% confidence interval (CI) 0.98-2.67), particularly among ever smokers (OR 2.10, 95% CI 1.07-5.33) and, among 677 TT individuals, those with a low intake of fruit and vegetables (OR 2.18, 95% CI 1.05-4.54). The strongest effect, however, was noted for the MTHFR 677 TT genotype among the diffuse gastric cancer histotype (OR 2.92, 95% CI 1.12-7.60). No association was detected for the effect of MTHFR A1298C polymorphism. Survival analysis did not show any association between each polymorphism on the overall survival, although when the analysis was restricted to the first year of follow-up after the surgical intervention an improved survival was noted among MTHFR 677 CC subjects compared with the T allele carriers (p value for log-rank test 0.02). In conclusion, MTHFR 677 (any T genotype) appears to modulate an individual's susceptibility to gastric cancer, particularly when combined with cigarette smoking and among those with a low intake of fruit and vegetables. Our results also suggest that an aberrant DNA methylation pattern, through impaired folate metabolism, might play a key role in gastric carcinogenesis. A possible survival effect of the MTHFR C677T genotype in gastric cancer patients deserves further investigations with larger sample sizes.

Genetic polymorphisms in folate metabolism and the risk of stomach cancer

Folate deficiency has been implicated in the etiology of stomach cancer through abnormal DNA methylation and disrupted DNA synthesis and repair. Enzyme-coding genes involved in folate metabolism are often polymorphic. In a population-based study of 305 cases and 427 controls in Warsaw, Poland, we evaluated the risk of stomach cancer in relation to polymorphisms in folate-metabolizing genes, including MTHFR (Ex5+79C>T and Ex8-62A>C), MTR (Ex26-20A>G), and MTRR (Ex2-64A>G, Ex5+123C>T, Ex15+572C>T, Ex15-405A>T, Ex9-85C>T, Ex15-526G>A, and Ex14+14C>T). Polymorphisms in the MTHFR gene were not associated with stomach cancer risk. No notable effect was found for polymorphisms in MTR or MTRR either, although MTR Ex26-20 A>G and MTRR Ex5+123C>T polymorphisms were associated with a borderline increased risk of stomach cancer (MTR Ex26-20A>G, AG/GG versus AA: odds ratio, 1.35; 95% confidence interval, 0.96-1.90; MTRR Ex5+123C>T, CT/TT versus CC: odds ratio, 1.30; 95% confidence interval, 0.93-1.82). We did not find significant interactions between polymorphisms in MTHFR, MTR, and MTRR genes and dietary folate and alcohol consumption. Our study did not identify strong genetic determinants in the folate metabolism pathway for stomach cancer risk.

Polymorphisms of 5,10-methylenetetralydrofolate reductase (MTHFR), fruit and vegetable intake, and the risk of stomach cancer

Stomach cancer is a serious public health problem in China. 5,10-Methylenetetralydrofolate reductase (MTHFR) may be involved in both DNA methylation and DNA synthesis. Folate deficiency is associated with cancer risk that may be modulated by a genetic variation in the MTHFR gene in folate metabolism. The main goal of this study was to evaluate the association between polymorphisms of the MTHFR gene and the risk of stomach cancer. This study also explored the modification effects of fruit and vegetable intake (one of the main constituents is folate) on the risk of this disease. A population-based case-control study was conducted in Taixing, China, consisting of 206 newly diagnosed cases with primary stomach cancer and 415 healthy population controls. Polymorphisms of MTHFR C677T and A1298C were assayed by polymerase chain reaction-restricted fragment length polymorphism (PCR-RFLP) techniques. The data were analysed using the logistic regression model. No obvious association between the MTHFR A1298C polymorphism and the risk of stomach cancer was observed in this study. The frequencies of 677 C/C, C/T, and T/T were 34.5, 50.9, and 14.6%, respectively, in controls. The frequency of the MTHFR 677 wild homozygotic genotype was 25.8% in cases, which was lower than that in controls (34.5%). The adjusted odds ratio (OR) for the MTHFR 677 any T genotype was 2.05 (95% confidence interval (CI), 1.26-3.34) when compared with the C/C genotype. In the low fruit and vegetable intake group an increasing trend was observed with the T allele exposure, p = 0.0056. The adjusted ORs were 1.68 (95% CI = 0.86-3.29) for the C/T genotype and 3.58 (95% CI = 1.46-8.75) for the T/T genotype, respectively. The MTHFR 677 any T genotype was associated with an increased risk of primary stomach cancer among the Chinese population. Folate deficiency might modify the MTHFR gene polymorphism and influence the risk of stomach cancer.

Association of the methylenetetrahydrofolate reductase C677T polymorphism and fracture risk in Chinese postmenopausal women

Osteoporotic fractures are a leading cause of disability and, indirectly, of death in the elderly population. Previous studies have shown that homocysteine level and the C677T polymorphism in the gene encoding methylenetetrahydrofolate reductase (MTHFR) may be involved in the development of osteoporosis and its related fracture in European populations. The aim of this study was to verify the association of this polymorphism with bone mineral density (BMD) and fractures in our 1899 Chinese postmenopausal women. The C677T T allele frequency in this population was 39.2%. The distribution of the MTHFR genotypes followed the Hardy-Weinberg equilibrium. BMD at total body, total hip or femoral neck did not significantly vary with MTHFR C677T genotype. The T allele carrier tended to have higher risk of having osteoporosis or osteopenia, but the difference was statistically insignificant. However, Poisson regression analysis revealed that the T allele carriers had an increased risk of fractures (RR=1.7, 95% CI=1.1-2.7, p=0.01) which occurred before or after menopause. As far as fracture incidence after menopause was concerned, the CT or TT genotype had more than twice the risk of the CC genotype (RR=2.5, 95% CI=1.2-4.9, p=0.009). This association was independent of age, physical activity, occupation, passive smoking, height, weight, years since menopause, and total hip BMD. Our data show that the MTHFR C677T polymorphism is an independent predictor of fracture risk, although it only had a weak effect on BMD. Further study on the mechanistic role that this polymorphism plays in the development of fractures may lead to better understanding of the etiology of osteoporotic fracture.

Methylenetetrahydrofolate reductase (MTHFR) and breast cancer risk: a nested-case-control study and a pooled meta-analysis

BACKGROUND

A reduced activity of methylenetetrahydrofolate reductase (MTHFR) due to frequent C677T polymorphism affects DNA synthesis, repair and methylation and may be implicated in breast cancer risk.

METHODS

We conducted a nested case-control study within a phase III prevention trial of tamoxifen. After a median follow-up of 81.2 months, 79 of the 5,408 hysterectomised women aged 35-70 years, who had received either tamoxifen 20 mg/day or placebo for 5 years, developed breast cancer. A total of 46 breast cancer cases and 80 unaffected controls matched to treatment allocation, years from randomization (+/-2 years) and age at randomization (+/-5 years), underwent genotyping for MTHFR C677T polymorphism using real time PCR.

RESULTS

The MTHFR 677 genotype frequencies for CC, CT, TT in breast cancer cases were 30%, 44% and 26%, respectively, and 35%, 51%, 14% in controls. We observed a borderline significant odds ratio of 2.51 (95% CI, 0.96-6.55) of breast cancer in subjects with 677TT genotype, with no further association after stratifying for age and treatment group. A meta-analysis of 18 studies, including our own, showed an increased risk of breast cancer in premenopausal women with 677TT genotype, with an odds ratio of 1.42 (95% CI, 1.02-1.98).

CONCLUSIONS

Our study lends support to a positive association between the MTHFR variant homozygous allele 677TT and breast cancer risk. Additional studies are warranted to provide further insight into the role of folate metabolism deficiency and breast cancer.

Gene polymorphisms of folate metabolizing enzymes and the risk of gastric cancer

Multiple studies have reported an association between disturbances of folate metabolism and increased risk of gastric cancer, including low intake of folate, low levels of folate in blood or genetic factors affecting folate metabolism. Among the genetic factors, in particular a common polymorphism in the gene encoding for 5,10-methylenetetrahydrofolate reductase (MTHFR C677T) has been linked to gastric cancer. Other polymorphisms in folate-metabolising genes have been less frequently investigated. Therefore, we analyzed this polymorphism, the glutamate carboxypeptidase (GCP) II C1561T and the reduced folate carrier (RFC) G80A in a case-control study involving 106 patients with histologically confirmed and characterized gastric cancer with adjustment for other established risk factors for gastric cancer in comparison to 106 age- and sex-matched controls. Neither the MTHFR nor the GCP gene polymorphisms showed an association to cancer diagnosis, to tumor stage, grade of differentiation or Lauren type. However, non-cardia cancers were more likely to exhibit the 80GA and 80AA RFC genotypes, compared to cancers of the gastric cardia (adjusted OR 0.28; 95% CI=0.11-0.71). Thus, gene polymorphisms of the RFC gene might contribute to an increased risk of developing distal gastric cancer.

Folate levels in mucosal tissue but not methylenetetrahydrofolate reductase polymorphisms are associated with gastric carcinogenesis

AIM: To evaluate whether folate levels in mucosal tissue and some common methylenetetrahydrofolate reductase (MTHFR) variants are associated with the risk of gastric cancer through DNA methylation.

METHODS: Real-time PCR was used to study the expression of tumor related genes in 76 mucosal tissue samples from 38 patients with gastric cancer. Samples from the gastroscopic biopsy tissues of 34 patients with chronic superficial gastritis (CSG) were used as controls. Folate concentrations in these tissues were detected by the FOL ACS: 180 automated chemiluminescence system. MTHFR polymorphisms were analyzed by PCR-RFLP, and the promoter methylation of tumor-related genes was determined by methylation-specific PCR (MSP).

RESULTS: Folate concentrations were significantly higher in CSG than in cancerous tissues. Decreased expression and methylation of c-myc accompanied higher folate concentrations. Promoter hypermethylation and loss of p16^INK4A in samples with MTHFR 677CC were more frequent than in samples with the 677TT or 677CT genotype. And the promoter hypermethylation and loss of p21^WAF1 in samples with MTHFR 677CT were more frequent than when 677CC or 677TT was present. The 677CT genotype showed a non-significant higher risk for gastric cancer as compared with the 677CC genotype.

CONCLUSION: Lower folate levels in gastric mucosal tissue may confer a higher risk of gastric carcinogenesis through hypomethylation and overexpression of c-myc.

Methyl group metabolism gene polymorphisms as modifier of breast cancer risk in Italian BRCA1/2 carriers

BRCA1 and 2 are major cancer susceptibility genes but their penetrance is highly variable. The folate metabolism plays an important role in DNA methylation and its alterated metabolism is associated with cancer risk. The role of allele variants 677T and 1298C (MTHFR gene) and 2756G (MS gene) has been investigated as potentially modifying factors of BRCA gene penetrance, evaluated as age at first diagnosis of cancer, in 484 BRCA1/BRCA2 carriers and in 108 sporadic breast cancer cases as a control group. The genotype analysis has been performed by means of PCR/RFLP's. The analysis of association between a particular genotype and disease risk was performed using Cox Regression with time to breast or ovarian cancer onset as the end-point. The presence of 677T allele confers an increased risk of breast cancer in BRCA1 carriers (P = 0.007) and the presence of 1298C allele confers an increased risk of breast cancer in sporadic cases (P = 0.015).

Methylenetetrahydrofolate reductase polymorphisms modify BRCA1-associated breast and ovarian cancer risks

Methylenetetrahydrofolate reductase (MTHFR), a key regulatory enzyme in the metabolism of folate, is suspected to play a role in the etiology of cancer, via its effects on DNA methylation and nucleotide synthesis. In this study we have investigated the effect of two functional polymorphisms of the MTHFR gene, MTHFR_677_C > T and MTHFR_1298_A > C, on breast and ovarian cancer risk in Polish BRCA1 mutation carriers. The study included 319 breast cancer cases, 146 ovarian cancer cases and 290 controls unaffected by breast and ovarian cancer, in situ breast cancer or any other kind of cancer. Genotyping analysis was performed using polymerase chain reaction followed by restriction fragment length polymorphism analysis. Odds ratios (OR) were calculated using univariate and multivariate logistic regression taking into account a series of confounding variables that potentially could have biased any association. The results revealed that the MTHFR_677_C > T change was associated with an increased risk of breast and ovarian cancer. The MTHFR_1298_A > C polymorphism was only associated with a decrease in breast cancer risk. Together, it appears that functional polymorphisms in the MTHFR gene modify the risk of breast and may potentially alter the risk of ovarian cancer in women with an inherited predisposition.

Folate intake, MTHFR polymorphisms, and risk of esophageal, gastric, and pancreatic cancer: a meta-analysis

BACKGROUND & AIMS

Increasing evidence suggests that a low folate intake and impaired folate metabolism may be implicated in the development of gastrointestinal cancers. We conducted a systematic review with meta-analysis of epidemiologic studies evaluating the association of folate intake or genetic polymorphisms in 5,10-methylenetetrahydrofolate reductase (MTHFR), a central enzyme in folate metabolism, with risk of esophageal, gastric, or pancreatic cancer.

METHODS

A literature search was performed using MEDLINE for studies published through March 2006. Study-specific relative risks were weighted by the inverse of their variance to obtain random-effects summary estimates.

RESULTS

The summary relative risks for the highest versus the lowest category of dietary folate intake were 0.66 (95% confidence interval [CI], 0.53-0.83) for esophageal squamous cell carcinoma (4 case-control), 0.50 (95% CI, 0.39-0.65) for esophageal adenocarcinoma (3 case-control), and 0.49 (95% CI, 0.35-0.67) for pancreatic cancer (1 case-control, 4 cohort); there was no heterogeneity among studies. Results on dietary folate intake and risk of gastric cancer (9 case-control, 2 cohort) were inconsistent. In most studies, the MTHFR 677TT (variant) genotype, which is associated with reduced enzyme activity, was associated with an increased risk of esophageal squamous cell carcinoma, gastric cardia adenocarcinoma, noncardia gastric cancer, gastric cancer (all subsites), and pancreatic cancer; all but one of 22 odds ratios were >1, of which 13 estimates were statistically significant. Studies of the MTHFR A1298C polymorphism were limited and inconsistent.

CONCLUSIONS

These findings support the hypothesis that folate may play a role in carcinogenesis of the esophagus, stomach, and pancreas.