Impact of methylenetetrahydrofolate reductase (MTHFR) codon (677) and methionine synthase (MS) codon (2756) on risk of cervical carcinogenesis in North Indian population

3'UTR polymorphism of Thymidylate Synthase gene increased the risk of persistence of pre-neoplastic cervical lesions

BACKGROUND

Cervical cancer is caused by high-risk Human Papillomavirus (hr-HPV) infection associated with cofactors that has been analyzed as predictors of the remission or persistence of cytological abnormalities remission or persistence. These cofactors can be either environmental, epigenetic, or genetic. Polymorphism in genes of enzymes that act on one-carbon metabolism alter their activity and also may be associated with cervical carcinogenesis because they affect DNA synthesis and repair, and gene expression. Therefore, this study aimed to analyze the risk of persistence of pre-neoplastic cervical lesions according to genetic polymorphisms involved in one-carbon metabolism.

METHODS

Our sample consisted of 106 women, divided into two groups - Remission (n = 60), i.e., with the presence of pre-neoplastic lesions at first meeting (T₁) and normal cytology after 6 months of follow-up (T₂), and Persistence (n = 46), i.e., with the presence of pre-neoplastic lesions at T₁ and T₂. We obtained cervical samples for cytological analysis (T₁ and T₂), HPV detection (T₁), and evaluation of polymorphism C667T of Methylenetetrahydrofolate Reductase (MTHFR C677T), A2756G of Methionine Synthase (MS A2756G), A66G of Methionine Synthase Reductase (MTRR A66G), double or triple 28 bp tandem repeat in 5'-untranslated enhanced region of Thymidylate Synthase (TSER), and 6 bp deletion at nucleotide 1494 in TS 3'-untranslated region (TS3'UTR). To analyze all genetic polymorphisms simultaneously, we calculated the Genetic Risk Score (GRS).

RESULTS

We observed no differences between the Remission and Persistence groups regarding the GRS. Also, there were no differences in the genotypic and allelic distribution of MTHFR C677T and MS A2756G polymorphisms. However, the risk of persistence was higher among women with the heterozygote genotype - ins/del [OR (IC95%): 3.22 (1.19-8.69), p = 0.021], or the polymorphic genotype - del/del [OR (IC95%): 6.50 (1.71-24.70), p = 0.006] of TS3'UTR.

CONCLUSIONS

The presence of the TS3'UTR polymorphism increased the risk of persistence of cervical abnormalities. This genetic variant could be a potential marker of cervical carcinogenesis and therefore assist the follow-up of women with persistent pre-neoplastic cervical lesions.

Association of MTHFR 677C>T Polymorphism with Susceptibility to Ovarian and Cervical Cancers: A Systematic Review and Meta-Analysis

Background:

Previous studies have evaluated the impact of MTHFR 677C>T polymorphism on susceptibility to ovarian and cervical cancers in women, but the conclusions are still controversial. To get a more precise evaluation of the association between MTHFR 677C>T polymorphism and risk of ovarian and cervical cancers, we performed a meta-analysis of the association of all eligible studies.

Methods:

A comprehensive search performed in PubMed, Google Scholar, CNKI, and Web of Science databases to identify the relevant studies up to October 15, 2018. The strength of the association was estimated by odds ratios (OR) with 95% confidence interval (CI).

Results:

A total of 27 case-control studies including eleven studies with 4990 cases 7730 controls on ovarian cancer and 16 studies with 4990 cases and 7730 controls on cervical cancer were selected. Pooled data revealed that the MTHFR 677C>T polymorphism not significantly associated with an increased risk of ovarian and cervical cancers under all five genetic models. However, stratified analysis by ethnicity showed that the MTHFR 677C>T polymorphism was significantly associated with risk of ovarian cancer in Asians. No publication bias was found in the current meta-analysis.

Conclusions:

The results of this meta-analysis proposes that the MTHFR 677C>T polymorphism may not play a role in development of ovarian and cervical cancers in overall population. Further well-designed studies are necessary to clarify the precise role of the MTHFR 677C>T polymorphism on ovarian and cervical cancers risk.

Association of Genetic Variants with Hyperhomocysteinemia in Indian Patients with Thrombosis

Hyperhomocysteinemia known to be associated with increased thrombotic tendency has been considered as a risk factor for coronary artery disease, atherosclerosis, venous thrombosis, and stroke. There are three main genes MTHFR, cystathionine beta-synthase (CBS) and methionine synthase (MS) and it's genetic variant that are known to influence the homocysteine metabolism leading to hyperhomocysteinemia. There is scarcity of Indian data on hyperhomocysteinemia and genetics variants in patients with thrombosis. Hence the objective of present study was to determine MTHFR, CBS, and MS genetic variants in thrombosis patients from Indian population. Genetic variant analysis was performed on thrombosis patients to detect MTHFR C677T (rs1801133), MTHFR A1298C (rs1801131), MS A2756G (rs1805087) and CBS T833C (rs5742905) mutations. The mutant allele frequencies of MTHFR 677T, MTHFR 1298C, MS2756G and CBS 833C were observed to be 16.1%, 37.5%, 34.1% and 5.8% respectively. MTHFR 677TT genotype was observed to be significantly associated with elevated homocysteine (Hcy) levels (64.65 μmol/L) alleles as compared to CC alleles (32.43 μmol/L) and CT alleles (30.54 μmol/L). MTHFR A1298C, MS A2756G and CBS T833C genotypes did not showed significant association with higher Hcy levels. Thus, in Indian patients with thrombosis only MTHFR T677T genotype was observed to be significantly associated with hyperhomocysteinemia.

Meta-Analysis of Polymorphic Variants Conferring Genetic Risk to Cervical Cancer in Indian Women Supports CYP1A1 as an Important Associated Locus

Objective: Association of multiple polymorphic variants with cervical cancer has been elucidated by several candidate gene based as well as genome-wide association studies. However, contradictory outcomes of those studies have failed to estimate the true effect of the polymorphic variants on cervical cancer. Methods: Literature mining of the PubMed database was done to gather all the publications related to genetic association with cervical cancer in India. Out of 98 PubMed hits only 29 genetic association studies were selected for meta-analysis based on specific inclusion criteria. A fixed-effect meta-analysis was performed to evaluate the overall association of the genetic polymorphisms with cervical cancer. Cochran’s Q test was performed to assess between study heterogeneity. Publication bias was also estimated by funnel plots and Egger’s regression test. Further, sub-group analysis was conducted by fixed-effect meta-regression to assess the impact of polymorphisms on cervical cancer in the presence of Human Papilloma Virus (HPV). Result: Following a fixed-effect model, meta-analysis was conducted that revealed 2 polymorphic variants viz. ‘deletion polymorphism (Del2) (OR=1.79, 95% CI= 1.08-2.95, P=0.023) in GSTM1’ and ‘rs1048943 (OR = 2.34, 95% CI=1.37-3.99, P=0.0018) in CYP1A1’ to be associated with cervical cancer. However, multiple testing correction showed only rs1048943 of CYP1A1 to be significantly associated (P-value=0.029) with cervical cancer with significant publication bias (P-value=0.0113) as estimated by Egger’s regression test. The polymorphic variants ‘rs1801131’, ‘rs1801133’, ‘rs2430561’, ‘rs1799782’, ‘rs25486’ and ‘rs25487’ showed significant (p<0.05) evidence of heterogeneity between studies by Cochran’s Q test and also by heterogeneity index (I2) calculation. Conclusion: Therefore, our study revealed significant association of rs1048943 in CYP1A1, but a nominal association of deletion polymorphism (Del2) in GSTM1 with cervical cancer, which provides a comprehensive insight on the true effect of the polymorphisms, reported in various case-control studies, on the risk of the development of cervical cancer in Indian women.

The association between MTHFR polymorphism and cervical cancer

Cervical cancer is an extremely prevalent disease worldwide. The purpose of this study was to illustrate the relationship between methylenetetrahydrofolate reductase (MTHFR) polymorphisms or methionine synthase reductase (MTRR) polymorphisms and cervical cancer. There were 372 women who performed genetic and folic acid assessments. For the MTHFR C677T, there was no significant difference in the distribution of C allele and T allele in the three groups. However, the mutant C allele of MTHFR A1298C was significantly higher in the cancer group than in the normal group. Similarly, the mutant G allele of MTRR A66G was also higher than the normal group. The serum folic acid levels were gradually decreased with the development of cervical lesions. Serum folate levels in 4–9 ng/ml and ≤4 ng/ml were both significantly associated with cervical cancer risk. However, the MTHFR C677T polymorphism was not associated with the risk of cervical cancer or CIN. In contrast, the MTHFR A1298C polymorphism could increase the risk of both cervical cancer and CIN. In addition, the MTRR A66G polymorphism was only associated with the risk of cervical cancer but not CIN.

The association between MTHFR polymorphisms and cervical cancer risk: a system review and meta analysis

PURPOSE

Methylenetetrahydrofolate reductase (MTHFR) plays an important role in determining the proportions of folate coenzymes for DNA synthesis or DNA methylation. Published data on the association between the MTHFR polymorphisms and cervical risk are controversial. A meta-analysis was performed to assess whether the polymorphisms of MTHFR are associated with cervical cancer risk.

METHODS

Medline, Embase, China National Knowledge Infrastructure and Chinese Biomedicine Databases were searched to identify eligible studies. Pooled odds ratios (ORs) and 95 % confidence intervals (CIs) for MTHFR C677T and MTHFR A1298C polymorphisms and cervical cancer were appropriately derived from fixed-effects or random effects models. Five different ORs were calculated: (1) allele contrast (C vs. T), (2) homozygous comparison (CC vs. TT), (3) heterozygous comparison (CC vs. CT), (4) dominant model (CC vs. CT+TT) and (5) recessive model (CC+CT vs. TT).

RESULTS

A total of 13 studies, which included 12 studies for MTHFR C677T (2332 cases and 3000 controls) and five studies for A1298C polymorphisms (677 cases and 1191 controls), were enrolled in this meta-analysis. The pooled analyses revealed that MTHFR C677T polymorphism was not associated with cervical cancer risk; while the A1298C polymorphism had a significant association with increased cervical cancer risk in allele contrast, heterozygote comparison and dominant model (A C, OR = 0.84, 95 % CI = 0.71-0.98; AA vs. CC OR = 0.72, 95 % CI = 0.59-0.89; AA vs. AC+CC, OR = 0.72, 95 % CI = 0.59-0.88). The significant associations between MTHFR A1298C polymorphism and cervical cancer were found among Asians and population-based case-control studies.

CONCLUSIONS

This study indicated that the MTHFR C677T may be no associated with cervical cancer risk, and yet the MTHFR A1298C polymorphism may be a risk factor for cervical cancer.

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.

Polymorphisms in genes involved in folate metabolism modify the association of dietary and circulating folate and vitamin B-6 with cervical neoplasia

High folate intake has been suggested as an important factor in cancer prevention; however, previous studies on the relation among folate intake, serum folate, and plasma homocysteine (hcy) are controversial. We conducted a hospital-based, case-control study in Brazil investigating associations between dietary and circulating vitamins B-6 and B-12 and folate, hcy, genotypes of folate-metabolizing enzyme methylenetetrahydrofolate reductase (MTHFR C677T, A1298C), 5-methyltetrahydrofolate-homocysteine methyltransferase (MTR A2756G), methionine synthase reductase (MTRR A66G), and reduced folate carrier (RFC1 G80A) and risk of cervical intraepithelial neoplasia (CIN) grades 1 (CIN1), 2 (CIN2), and 3 (CIN3). The study was composed by 453 controls, 140 CIN1, 126 CIN2, and 231 CIN3. We investigated the joint effects of genetic variants of folate-related genes using genetic risk scores (GRSs) by summing the number of risk alleles for CIN1 and CIN2+ (CIN2 and CIN3 cases). The OR (95% CI) for CIN1 and CIN2+ per each risk allele were 1.29 (1.01, 1.65) and 1.22 (1.01, 1.46), respectively. An association between folate intake and CIN2+ was observed only after stratification according to GRS: crude OR (95% CI) for lower folate intake and GRS ≥ 4 was 1.67 (0.92, 3.04) (P-trend < 0.001) compared with higher folate intake (above the median) and GRS ≤ 3. The CIN2+ risk of lower serum vitamin B-6 and GRS ≥ 4 was 2.14 (0.92, 5.02) (P-trend = 0.05) and lower serum folate (below the median) and GRS ≥ 4 was 0.49 (0.20, 1.17) (P-trend = 0.05) after adjustment for confounding variables and human papillomavirus infection. Our data suggest that polymorphisms in genes related to folate metabolism modify the association of dietary and circulating folate and vitamin B-6 with cervical neoplasia.

MTHFR C677T polymorphism was an ethnicity-dependent risk factor for cervical cancer development: evidence based on a meta-analysis

INTRODUCTION

Many studies have studied the associations between 5, 10-methylene tetrahydrofolate reductase (MTHFR) polymorphisms and susceptibilities of cervical cancer and cervical intraepithelial neoplasia (CIN); however, the results were inconsistent. The aim of this study was to further assess the relationships by the method of meta-analysis.

MATERIALS AND METHODS

Two investigators independently searched the PubMed, Embase, Wang Fang (Chinese database) and CNKI (China National Knowledge Infrastructure), with latest update to July 1st, 2011. The pooled odds ratio (OR) and 95 % confidence interval (95 % CI) were used to assess the strength of the associations by using fixed- or random-effect model.

RESULTS

Ten case-control studies were included in this meta-analysis including a total of 1,803 cervical cancer or CIN cases and 2,363 controls. Pooled analyses showed that T allele of MTHFR C677T was significantly associated with increased CIN risk [OR (95 % CI): 1.28 (1.03-1.50) for CT vs. CC], especially for low-grade CIN risk. In addition, MTHFR C677T rather than A1298C polymorphism was associated with risk of cervical cancer. Stratifying analyses for ethnicity indicated that T allele of MTHFR C677T was associated with increased cervical cancer risk for Asian [OR (95 % CI): 1.56 (1.17-2.08) for TT vs. CC; 1.53 (1.19-1.96) for TT vs. C carriers] while decreased risk for Caucasian [OR (95 % CI): 0.63 (0.45-0.89) for TT vs. CC; 0.66 (0.56-0.79) for T carriers vs. CC].

CONCLUSION

This meta-analysis suggested that there was no association between MTHFR A1298C polymorphism and cervical cancer risk. However, MTHFR C677T was an ethnicity-dependent risk factor for cervical cancer occurrence. In addition, T allele of C677T was significantly associated with risk of low grade of CIN incidence. Because of modest limitations of our study, well-designed studies with large sample size were needed to confirm our findings in the future.

Association between MTHFR C677T, MTHFR A1298C and MS A2756G polymorphisms and risk of cervical intraepithelial neoplasia II/III and cervical cancer: a meta-analysis

Numerous case-control studies on the association between polymorphisms of key genes involved in methionine remethylation [methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MS)] and the susceptibility of cervical intraepithelial neoplasia (CIN) and cervical cancer have provided inconclusive results. The aim of the present meta-analysis was to determine the effects of two MTHFR (C677T and A1298C) and one MS gene polymorphism (A2756G) on the risk of CIN II/III or cervical cancer. Relevant data were retrieved following a systematic search in PubMed, Web of Science, MEDLINE and Wanfang Data up to November 2012. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were estimated from eligible studies by meta-analysis with subgroup analyses stratified by ethnicity. A total of 13 studies with 1,936 cases and 2,858 controls were included in the present meta‑analysis. An increased risk of cervical cancer was found in Asian women with the MTHFR 677T allele (TT vs. CC: OR=1.41, 95% CI=1.07‑1.86, P=0.01; TT vs. CC+CT: OR=1.38, 95% CI=1.08-1.75, P=0.008), while a decreased risk was observed in Caucasian women (TT vs. CC: OR=0.65, 95% CI=0.45-0.93, P=0.02; TT+CT vs. CC: OR=0.7, 95% CI=0.58-0.86, P=0.0005). No effects of MTHFR C677T polymorphism on CIN II/III risk and MTHFR A1298C or MS A2756G polymorphisms on cervical cancer risk were detected. The sensitivity analysis suggested stability of this meta-analysis and no publication bias was detected. The MTHFR 677T allele may enhance the risk of cervical cancer in the Asian female population and play a protective role in Caucasian females. However, limited association is suggested between MTHFR A1298C and MS A2756G polymorphisms with cervical tumorigenesis.

C677T polymorphism of methylenetetrahydrofolate reductase may contribute to cervical cancer risk in complete over-dominant model

PURPOSE

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in the metabolism of folate. The single nucleotide polymorphism (SNP), C677T (Ala>Val, rs1801133), has been confirmed to decrease the enzyme activity. The association between C677T and cervical cancer susceptibility has been widely studied. However, the results were inconsistent. In order to elucidate the role of this SNP in cervical cancer, a meta-analysis was conducted.

METHODS

The literature search was performed using the following databases: PubMed, Embase and ISI Web of Science up to December 2012. The effect of association was indicated as crude odds ratio (OR) with the corresponding 95% confidence interval (CI).

RESULTS

Six studies including 1431 cases and 1915 controls explored C677T genotypes were involved in this meta-analysis. Overall meta-analysis showed that C677T polymorphism increased cervical cancer risk in the complete over-dominant model (random-effect OR=1.33, 95% CI: 1.00-1.77, I(2)=69%). After excluding one study which showed apparent heterogeneity, the heterogeneity disappeared. The meta-analysis of five studies including 1231 cases and 1715 controls showed the fixed-effect OR reached 1.20 (95% CI: 1.03-1.40, I(2)=0) as (TT+CC) in the complete over-dominant model.

CONCLUSIONS

C677T polymorphism of MTHFR gene may increase the risk of cervical cancer in the complete over-dominant model. The association merits replicating and validating in further studies.

Association between Methylenetetrahydrofolate reductase C677T polymorphism and susceptibility to cervical cancer: a meta-analysis

Background

To assess the association between MTHFR polymorphism and cervical cancer risk, a meta-analysis was performed.

Methods

Based on comprehensive searches of the PubMed, Embase, and Web of Science databases, we identified outcome data from all articles estimating the association between MTHFR polymorphism and cervical cancer risk. The pooled odds ratio (OR) with 95% confidence intervals (CIs) were calculated.

Results

A total of 12 studies with 2,924 cases (331 cervical intraepithelial neoplasia (CIN) I, 742 CIN II/III, 1851 invasive cervical cancer) and 2,581 controls were identified. There was no significant association between MTHFR C677T polymorphism and CIN I risk (T vs. C, OR = 1.10, 95% CI = 0.92–1.31; TT vs. CC, OR = 1.14, 95% CI = 0.78–1.68; TT+CT vs. CC, OR = 1.22, 95% CI = 0.94–1.58; TT vs. CT+CC, OR = 0.99, 95% CI = 0.70–1.40). For the CIN II/III, lack of an association was also found (T vs. C, OR = 1.08, 95% CI = 0.95–1.23; TT vs. CC, OR = 1.15, 95% CI = 0.87–1.52; TT+CT vs. CC, OR = 1.13, 95% CI = 0.94–1.35; TT vs. CT+CC, OR = 1.07, 95% CI = 0.83–1.38). The T allele had significant association to susceptibility of invasive cervical cancer in recessive model (TT vs. CT+CC, OR = 1.23, 95% CI = 1.02–1.49). On subgroup analysis by ethnicity, similarly significant differences in T vs. C, TT vs. CC, and recessive model were found in Asians.

Conclusion

The present meta-analysis suggested that MTHFR C677T polymorphism were to substantially contribute to invasive cervical cancer in recessive model.

Methylenetetrahydrofolate reductase (MTHFR) polymorphisms and susceptibility for cervical lesions: a meta-analysis

Background

The association between the methylenetetrahydrofolate reductase (MTHFR) C677T/A1298C polymorphisms and the susceptibility to cervical lesions was unclear. This study was designed to investigate their precise association using a large-scale meta-analysis.

Methods

The previous 16 studies were identified by searching PubMed, Embase and CBM databases. The crude odds ratios and their corresponding 95% confidence intervals (CIs) were used to estimate the association between the MTHFR C677T/A1298C polymorphisms and the susceptibility to the cervical lesions. The subgroup analyses were made on the following: pathological history, geographic region, ethnicity, source of controls and source of DNA for genotyping.

Results

Neither of the polymorphisms had a significant association with the susceptibility to the cervical lesions in all genetic models. Similar results were found in the subgroup analyses. No association was found between the MTHFR C677T polymorphism and the cervical lesions in the Asia or the America populations though a significant inverse association was found in the Europe population (additive model: P = 0.006, OR = 0.83, 95% CI = 0.72–0.95; CT vs. CC: P = 0.05, OR = 0.83, 95% CI = 0.69–1.00; TT vs. CC: P = 0.05, OR = 0.73, 95% CI = 0.53–1.00). Interestingly, women with the MTHFR A1298C polymorphisms had a marginally increased susceptibility to invasive cancer (ICC) when compared with no carriers but no statistically significant difference in the dominant model (P = 0.06, OR = 1.21, 95% CI = 0.99–1.49) and AC vs. AA (P = 0.09, OR = 1.21, 95% CI = 0.97–1.51).

Conclusions

The MTHFR C677T and A1298C polymorphisms may not increase the susceptibility to cervical lesions. However, the meta-analysis reveals a negative association between the MTHFR C677T polymorphisms and the cervical lesions, especially in the European populations. The marginal association between the MTHFR A1298C polymorphisms and the susceptibility to cervical cancer requires a further study.

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.

Cervical cancer with polymorphism in MTHFR C677T gene: a systematic review and meta-analysis

To perform a meta-analysis investigating the association of MTHFR C677T polymorphism and susceptibility of cervical cancer. All case-control studies published in English and Chinese with estimates of the relationship between MTHFR C677T polymorphism and risk of cervical cancer were analyzed using odds ratio (OR) with 95 % confidence interval (CI). A total of 10 studies (2,023 cases and 2,570 controls) were included in the meta-analysis. No significant association was observed between T allele and C allele (OR = 0.90; 95 %CI = 0.70-1.17; P = 0.43), and for genotype TT versus CC (OR = 1.09; 95 %CI = 0.74-1.61; P = 0.67), CT versus CC (OR = 0.95; 95 %CI = 0.75-1.20; P = 0.65), CT + TT versus CC (OR = 0.91; 95 %CI = 0.66-1.24; P = 0.55). The current meta-analysis results suggest that the MTHFR C677T polymorphism may not be associated with cervical cancer.

Methylenetetrahydrofolate reductase C677T polymorphism and susceptibility to cervical cancer and cervical intraepithelial neoplasia: a meta-analysis

Background

A number of studies have explored the association between methyl enetetrahydrofolate reductase (MTHFR) C677T polymorphism and susceptibility to cervical cancer and cervical intraepithelial neoplasia (CIN). However, results remained controversial. To address this gap, we decided to conduct a meta-analysis of all available published studies.

Methods

Electronic literature searches of the PubMed, EmBase and Medline databases were performed up to April 30, 2012. Fixed-effects or random-effects model was used to calculate the pooled ORs for different genetic models.

Results

A total of 12 case-control studies were ultimately identified. No statistical correlation was found between C677T variants and cervical cancer for the overall population. However, subgroup analyses on the White women pointed to a significant protective effect for individuals heterozygous or homozygous for the T-allele (for CT vs. CC: OR = 0.72, 95% CI 0.59–0.88; for TT vs. CC: OR = 0.69, 95% CI = 0.49–0.97; for CT+TT vs. CC: OR = 0.71, 95% CI 0.59–0.86). C677T variants were associated with neither combined nor stratified CIN among the overall population.

Conclusions

This meta-analysis suggests that White women with mutant C677T genotypes might have a lower risk of cervical cancer, yet lacking enough statistical robustness. Further investigations are needed to get more insight into the role of this polymorphism in cervical carcinogenesis.

Association of the functional polymorphism C677T in the methylenetetrahydrofolate reductase gene with colorectal, thyroid, breast, ovarian, and cervical cancers

BACKGROUND

Polymorphisms of the gene encoding methylenetetrahydrofolate reductase (MTHFR) have been studied widely in various cancers, excluding thyroid cancer. However, reports on the association of various polymorphisms with certain cancers are contradictory.

MATERIALS AND METHODS

We have investigated whether the prevalence of the most common polymorphism (C677T) in the MTHFR gene has any link with various cancers, using genomic DNA and polymerase chain reaction restriction fragment length polymorphism (PCRRFLP) analysis.

RESULTS

The frequency of the heterozygous variant (677CT) but not that of 677TT was found to be significantly higher in colorectal cancer cases than in controls (p < 0.039; odds ratio 2.35 and 95% confidence interval 1.02-5.415). The frequencies for 677CT were 11.0 and 5.0% in colorectal cancer samples and controls, respectively. In ovarian cancer, the frequency of the 677TT variant was 6.0% which differed significantly (p < 0.026) from the control value of 1.0%. However, the frequencies of the variants in cervical, thyroid, and breast cancer cases did not differ from controls.

CONCLUSIONS

Our data taken together with other reports indicates that the polymorphism C677T of MTHFR is a risk factor for developing colorectal cancer but not cervical, thyroid, and breast cancers. The present study also reconfirms that frequencies of the variants are not gender-specific.

Evaluation of MTHFR677C>T polymorphism in prediction and prognosis of esophageal squamous cell carcinoma: a case-control study in a northern Indian population

Early diagnosis and better prognosis of esophageal squamous cell carcinoma (ESCC) is still a challenge. Besides environmental risk factors, nutritional deficiencies have an established role in pathogenesis of ESCC. Folate deficiency and functional polymorphisms in folate metabolizing genes such as methylene tetrahydrofolate reductase (MTHFR) 677C>T may have oncogenic role through disruption of normal DNA methylation pattern, synthesis, and impaired DNA repair. MTHFR677C>T or A222V (rs1801133) polymorphism has conflicting role in susceptibility to ESCC among different populations. Thus, we aimed to study the role of MTHFR677C>T polymorphism in susceptibility, survival, and interaction with environmental risk factors in ESCC patients from a northern Indian population. A case control study was performed in 208 ESCC incident cases (including 114 follow-up cases) and 223 healthy controls, and genotyping was done by PCR-RFLP. Our results show no significant association of MTHFR677C>T polymorphism with ESCC, tumor locations, or gender of subjects. However, we found a trend of decreased risk of ESCC due to interaction of MTHFR677CT genotype with smoking and alcohol intake. Kaplan Meier, and Cox regression survival analysis showed no prognostic impact of MTHFR677C>T polymorphism in ESCC patients. In conclusion, MTHFR677C>T polymorphism does not seem to have significant role either in susceptibility or survival of ESCC in a northern Indian population.

Polymorphisms in folate-metabolizing genes and risk of non-Hodgkin's lymphoma

We investigated the role of single nucleotide polymorphisms (SNPs) in the folate-metabolizing genes MTHFR, MTR, MTRR, MTHFD, CBS and SHMT in regulating genetic susceptibility to Non-Hodgkin's lymphoma (NHL). We determined the allele and genotype frequencies in the case group (146 patients with NHL) and the control group (540 blood donors). A significant association with NHL was observed only for MTHFD1 G1958A (allele G OR=1.382, P=0.05; genotype GA OR=2.316, P=0.01; genotype GG OR=2.153, P=0.03). After additional stratification of case and control groups according to sex and tumor type association of MTHFD1 G1958A with NHL was observed only in high-grade NHL subgroup (allele G OR=1.664, P=0.01) and in women subgroup (allele G OR=2.043, P=0.009). Meta-analysis for SNPs in the MTHFR, MTR, MTRR and SHMT revealed a reducing effect of the MTR 2756G allele on the risk of NHL (OR=0.902; 95% CI 0.821-0.991, P=0.03).

Methionine synthase A2756G polymorphism and cancer risk: a meta-analysis

Polymorphisms in methionine synthase (MTR) gene may be involved in carcinogenesis by affecting DNA methylation. However, association studies on MTR A2756G polymorphism in cancers have reported conflicting results. Therefore we performed a meta-analysis to better assess the associations. A total of 24 896 cancer patients and 33 862 controls from 52 articles for MTR A2756G were investigated. Overall, individuals carrying MTR 2756GG genotype had a subtly reduced cancer risk under a recessive genetic model (odds ratio (OR), 0.92; P=0.053; 95% confidence interval (95% CI), 0.84-1.00; I(2)=0.0%; P(heterogeneity)=0.61). In the subgroup analyses by ethnicity, 2756GG was associated with a significantly reduced cancer risk in European populations (OR, 0.83; P=0.001; 95% CI, 0.74-0.93; I(2)=0.0%; P(heterogeneity)=0.99). However, in Asian populations, a significantly elevated association between 2756GG genotype and cancer risk was observed (OR, 1.33; P=0.012; 95% CI, 1.06-1.65; I(2)=0.0%; P(heterogeneity)=0.50). In studies stratified by tumor site, there was a significantly reduced risk of acute lymphoblastic leukemia (ALL) (OR, 0.54; P=0.049; 95% CI, 0.29-1.00; I(2)=10.7%; P(heterogeneity)=0.33) and colorectal cancer (OR, 0.63; P=0.004; 95% CI, 0.47-0.87; I(2)=0.0%; P(heterogeneity)=0.73) in European populations. Our study indicates that MTR A2756G polymorphism is a candidate gene polymorphism for cancer susceptibility regardless of environmental factors. Large-scale, well-designed, and population-based studies are required to further investigate gene-gene and gene-environment interactions on MTR A2756G polymorphism and tissue-specific cancer risk in an ethnicity-specific population.