Quantitative assessment of the association between MTHFR C677T polymorphism and colorectal cancer risk in East Asians

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.

MTHFR C677T and A1298C polymorphism's effect on risk of colorectal cancer in Lynch syndrome

Lynch syndrome (LS) is characterised by an increased risk of developing colorectal cancer (CRC) and other extracolonic epithelial cancers. It is caused by pathogenic germline variants in DNA mismatch repair (MMR) genes or the EPCAM gene, leading to a less functional DNA MMR system. Individuals diagnosed with LS (LS individuals) have a 10-80% lifetime risk of developing cancer. However, there is considerable variability in the age of cancer onset, which cannot be attributed to the specific MMR gene or variant alone. It is speculated that multiple genetic and environmental factors contribute to this variability, including two single nucleotide polymorphisms (SNPs) in the methylenetetrahydrofolate reductase (MTHFR) gene: C677T (rs1801133) and A1298C (rs1801131). By decreasing MTHFR activity, these SNPs theoretically reduce the silencing of DNA repair genes and increase the availability of nucleotides for DNA synthesis and repair, thereby protecting against early-onset cancer in LS. We investigated the effect of these SNPs on LS disease expression in 2,723 LS individuals from Australia, Poland, Germany, Norway and Spain. The association between age at cancer onset and SNP genotype (risk of cancer) was estimated using Cox regression adjusted for gender, country and affected MMR gene. For A1298C (rs1801131), both the AC and CC genotypes were significantly associated with a reduced risk of developing CRC compared to the AA genotype, but no association was seen for C677T (rs1801133). However, an aggregated effect of protective alleles was seen when combining the alleles from the two SNPs, especially for LS individuals carrying 1 and 2 alleles. For individuals with germline pathogenic variants in MLH1, the CC genotype of A1298C was estimated to reduce the risk of CRC significantly by 39% (HR = 0.61, 95% CI 0.42, 0.89, p = 0.011), while for individuals with pathogenic germline MSH2 variants, the AC genotype (compared to AA) was estimated to reduce the risk of CRC by 26% (HR = 0.66, 95% CI 0.53, 0.83, p = 0.01). In comparison, no association was observed for C677T (rs1801133). In conclusion, our study suggests that combining the MMR gene information with the MTHFR genotype, including the aggregated effect of protective alleles, could be useful in developing an algorithm that estimates the risk of CRC in LS individuals.

The Roles of MTRR and MTHFR Gene Polymorphisms in Colorectal Cancer Survival

Background: Paradoxically epidemiological data illustrate a negative relationship between dietary folate intake and colorectal cancer (CRC) risk. The occurrence and progression of CRC may be influenced by variants in some key enzyme coding genes in the folate metabolic pathway. We investigated the correlation between genetic variants in methionine synthase reductase (MTRR) and methylenetetrahydrofolate reductase (MTHFR) and CRC survival. Methods: This study used data collected from the Newfoundland Familial Colorectal Cancer Study. A total of 532 patients diagnosed with CRC for the first time from 1999 to 2003 were enrolled, and their mortality were tracked until April 2010. DNA samples were genotyped by Illumina’s integrated quantum 1 million chip. Cox models were established to assess 33 tag single-nucleotide polymorphisms in MTRR and MTHFR in relation to overall survival (OS), disease-free survival (DFS) and CRC-specific survival. Results: The MTRR and MTHFR genes were associated with DFS and CRC-specific survival in CRC patients at the gene level. After multiple comparison adjustment, MTRR rs1801394 A (vs. G) allele was associated with increased DFS (p = 0.024), while MTHRT rs3737966 (G vs. A), rs4846049 (T vs. G), rs1476413 (A vs. G), rs1801131 (C vs. A), rs12121543 (A vs. C), rs1801133 (C vs. T), rs4846052 (T vs. C), rs2066471 (A vs. G) and rs7533315 (T vs. C) were related to worse CRC-specific survival. Additionally, significant interactions were seen among pre-diagnostic alcohol consumption with MTRR rs1801394, rs3776467, rs326124, rs162040, and rs3776455, with superior OS associated with those protective variant alleles limited to patients with alcohol consumption under the median. The MTHFR rs3737966 (G vs. A) allele seemed to be detrimental to CRC survival only among subjects with fruit intake below the median. Conclusions: Polymorphic variants in MTRR and MTHFR genes that code for key enzymes for folate metabolism may be associated with survival in patients with CRC. The gene-CRC outcome association seems modulated by alcohol drinking and fruit intake.

Methylenetetrahydrofolate reductase C677T polymorphism and colorectal cancer susceptibility: a meta-analysis

The association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and colorectal cancer (CRC) susceptibility has been researched in numerous studies. However, the results of these studies were controversial. Therefore, the objective of this meta-analysis was to offer a more convincible conclusion about such association with more included studies. Eligible studies published till May 1, 2017 were searched from PubMed, Embase, Web of Science, and CNKI database about such association. Pooled odds ratios (ORs) together with 95% confidence intervals (CIs) were calculated to evaluate such association. And the Begg's funnel plot and Egger's test were applied to assess the publication bias. This meta-analysis contained 37049 cases and 52444 controls from 87 publications with 91 eligible case-control studies. Because of lack of data for a particular genotype in several studies, all the included studies were analysed barely in the dominant model. Originally, there was no association between MTHFR C677T polymorphism and CRC susceptibility (OR =0.99, 95% CI =0.94-1.05). After excluding 13 studies according to their heterogeneity and publication bias, rs1801133 polymorphism was found to reduce the risks of CRC significantly (OR =0.96, 95% CI =0.94-0.99). In the subgroup analysis of ethnicity, there was a significant association in Asians (OR =0.94, 95% CI =0.89-1.00). Furthermore, when stratified by the source of controls and genotyping methods, the positive results were observed in population-based control group (OR =0.97, 95% CI =0.93-1.00) and PCR-restriction fragment length polymorphism (PCR-RFLP) method (OR =0.95, 95% CI =0.91-0.99. The results of the meta-analysis suggested that MTHFR C677T polymorphism was associated with CRC susceptibility, especially in Asian population.

Alcohol consumption, genetic variants in the alcohol- and folate metabolic pathways and colorectal cancer risk: the JPHC Study

The association between alcohol intake and colorectal cancer (CRC) may vary secondary to single nucleotide polymorphisms (SNPs) in two pathways related to alcohol intake. 375 cases of CRC were identified among 38 373 Japan Public Health Center-based prospective Study (JPHC Study) participants who had returned a baseline questionnaire, reported no diagnosis of any cancer and provided blood samples. For each case, two controls were selected on matching variables. Logistic regression models were used to determine matched Odds Ratios (OR) and 95% Confidence Intervals (CI) for the association between alcohol consumption, genetic polymorphisms of enzymes in the alcohol- and folate metabolic pathways (e.g. methylenetetrahydrofolate reductase (MTHFR) rs1801133) and CRC risk. Compared to never/occasional alcohol intake, moderate to heavy alcohol intake was associated with CRC (OR = 2.12, 95% CI, 1.34–3.36). When compared to the CC genotype, the MTHFR rs1801133 CT/TT genotype was inversely associated with CRC (OR = 0.72, 95% CI, 0.54–0.97). Never/occasional consumers of alcohol with the MTHFR rs1801133 CT/TT genotype were also at a reduced risk of CRC compared to never/occasional drinkers with the CC genotype (OR = 0.68, 95% CI, 0.47–0.98) (P for interaction = 0.27). The results indicate that the folate pathway is likely to be involved in alcohol-related CRC development.

MTHFR rs1801133 polymorphism and susceptibility to colorectal cancer in Iranian population: evidence of a case-control study and meta-analysis

Several studies have investigated whether MTHFR rs1801133 polymorphism contributes to risk of colorectal cancer (CRC), however the results are inconclusive.

AIM

The purpose of this study was to investigate this hypothesis in a case-control study and meta-analysis in Iranian population.

MATERIALS & METHODS

This polymorphism was genotyped in the 2421 subjects (46% CRC patients) from Tehran. Meta-analysis was performed for determining the risk effect size of this polymorphism on CRC.

RESULTS

Both case-control study and meta-analysis showed no association between rs1801133 and CRC risk or its features.

CONCLUSION

This study failed to identify an association between the rs1801133 and susceptibility to CRC in Iranian population.

Association between the TCF7L2 polymorphism and colorectal cancer does not differ by diabetes and obesity statuses

This study evaluated the association between polymorphism in a newly identified locus, rs11196172, located in transcription factors 7-like 2 (TCF7L2) and colorectal cancer (CRC) risk according to diabetes and obesity statuses. A study enrolled 6138 CRC patients and 4367 community controls. The adjusted odds ratios (aORs) with age, sex, smoking, and body mass index of the A allele, compared with the G allele, was 1.08 (95% CI 1.01-1.16). The significantly higher risk of CRC with the A allele remained after adjusting for diabetic status (aOR 1.07, 95% CI 1.01-1.15). When stratified by diabetic or obesity status, significant associations between TCF7L2 polymorphism and CRC risk were limited to non-diabetic or normal-weight subjects. No significant interactions between the A/G allele and diabetes status or the A/G allele and overweight status were found. The results indicated that the TCF7L2 rs11196172 polymorphism increases the risk of CRC independently, with no evidence of an interaction with diabetes or obesity.

Evaluation of association studies and meta-analyses of MTHFR gene polymorphisms in colorectal cancer

There is a discrepancy between the results of 89 original studies and 15 meta-analyses investigating the association of MTHFR rs1801133 and rs1801131 polymorphisms with colorectal cancer (CRC) risk. We examined this hypothesis through meta-analyses of both loci and their diplotypes as well as evaluation of previous meta-analyses. The present meta-analysis showed that rs1801133 and rs1801131 might be CRC susceptibility variants in Americans and Australians and rs1801133 in Brazilians and Japanese. A strong linkage disequilibrium was observed between both loci and their diplotypes were associated with CRC risk. Evaluation of 15 meta-analyses showed a high discrepancy among their findings, mainly caused by population stratification of original studies and data analysis strategies in meta-analysis. Population stratification was more dominant in the studies from Australia, America and Brazil leading to false positive or negative results. In conclusion, these loci alone might modify the development of CRC in some ethnicities.

Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism: epidemiology, metabolism and the associated diseases

The Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism is associated with various diseases (vascular, cancers, neurology, diabetes, psoriasis, etc) with the epidemiology of the polymorphism of the C677T that varies dependent on the geography and ethnicity. The 5,10-Methylenetetrahydrofolate reductase (MTHFR) locus is mapped on chromosome 1 at the end of the short arm (1p36.6). This enzyme is important for the folate metabolism which is an integral process for cell metabolism in the DNA, RNA and protein methylation. The mutation of the MTHFR gene which causes the C677T polymorphism is located at exon 4 which results in the conversion of valine to alanine at codon 222, a common polymorphism that reduces the activity of this enzyme. The homozygous mutated subjects have higher homocysteine levels while the heterozygous mutated subjects have mildly raised homocysteine levels compared with the normal, non-mutated controls. Hyperhomocysteinemia is an emerging risk factor for various cardiovascular diseases and with the increasing significance of this polymorphism in view of the morbidity and mortality impact on the patients, further prevention strategies and nutritional recommendations with the supplementation of vitamin B12 and folic acid which reduces plasma homocysteine level would be necessary as part of future health education. This literature review therefore focuses on the recent evidence-based reports on the associations of the MTHFR C677T polymorphism and the various diseases globally.

Associations between methylenetetrahydrofolate reductase polymorphisms and hepatocellular carcinoma risk in Chinese population

Genetic polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene are considered to have some influence on both folate metabolism and cancer risk. Previous studies on the associations of MTHFR genetic polymorphisms with hepatocellular carcinoma (HCC) risk in Chinese population reported inconsistent results. We performed this meta-analysis to comprehensively assess the associations. Finally, 12 individual case-control studies were included into the meta-analysis. There were seven studies (6,384 subjects) on the MTHFR C677T polymorphism and five studies (4,502 subjects) on the MTHFR A1298C polymorphism. Overall, MTHFR C677T polymorphism was significantly associated with susceptibility to HCC in Chinese population (T versus C, odds ratio (OR) = 1.09, 95 % confidence interval (95% CI) 1.01-1.17; TT versus CC, OR = 1.17, 95% CI 1.00-1.38; TT/CT versus CC, OR = 1.12, 95% CI 1.00-1.26). MTHFR A1298C polymorphism was conversely associated with HCC risk in Chinese population (CC versus AA, OR = 0.65, 95% CI 0.46-0.91; CC versus AA/AC, OR = 0.64, 95% CI 0.46-0.90). The sensitivity analysis confirmed the reliability and stability of the meta-analysis. Thus, the findings from our meta-analysis support the associations of MTHFR C677T and A1298C polymorphisms with HCC risk in Chinese population.

Significant association between MTHFR C677T polymorphism and hepatocellular carcinoma risk: a meta-analysis

Previous studies investigated the association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and hepatocellular carcinoma risk, but the impact of MTHFR C677T polymorphism on hepatocellular carcinoma was still unclear, owing to the obvious inconsistence from those studies. This study aimed to quantify the strength of the association between MTHFR C677T polymorphism and hepatocellular carcinoma risk by performing a meta-analysis. We searched the PubMed and Wanfang databases for studies on the association between MTHFR C677T polymorphism and hepatocellular carcinoma risk. We estimated the pooled odds ratios (ORs) with their 95% confidence intervals (95% CIs) to assess the association. Fifteen studies with 8,625 participants were finally included into the meta-analysis. Meta-analyses of total 15 studies suggested that MTHFR C677T polymorphism was significantly associated with an increased risk of hepatocellular carcinoma under two main genetic models (for TT versus CC, OR = 1.19, 95% CI 1.03-1.37, P = 0.016; for TT versus CT/CC, OR = 1.14, 95% CI 1.01-1.28, P = 0.032). Subgroup meta-analyses suggested that MTHFR C677T polymorphism was associated with an increased risk of hepatocellular carcinoma in Asians, but not in Caucasians. Thus, individuals with homozygote genotype TT of MTHFR C677T have obviously increased risk of hepatocellular carcinoma.

The effect of oxoguanine glycosylase 1 rs1052133 polymorphism on colorectal cancer risk in Caucasian population

Human oxoguanine glycosylase 1 (OGG1) is an important part of the base excision repair pathway in the DNA repair. Numerous epidemiological studies have evaluated the association between OGG1 rs1052133 polymorphism and the risk of colorectal cancer, but the results of these studies from the Caucasian population were conflicting. To derive a more precise assessment on the association between OGG1 rs1052133 polymorphism and risk of colorectal cancer in Caucasian population, we performed a meta-analysis. The odds ratios (OR) with 95% confidence intervals (CI) were used to assess the strength of the association. Thirteen case-control studies with a total of 4,103 cases and 5,400 controls were finally included into the meta-analysis. Meta-analysis of all 13 studies showed that OGG1 rs1052133 polymorphism was significantly associated with the risk of colorectal cancer in Caucasian population (Cys versus Ser OR = 1.20, 95% CI = 1.03-1.39, P = 0.02; CysCys versus SerSer OR = 1.44, 95% CI = 1.04-2.00, P = 0.03; CysCys versus SerSer/SerCys OR = 1.39, 95% CI = 1.15-1.67, P = 0.0005). In the sensitivity analysis, omitting each study one at a time had no obvious influence on the pooled OR, which confirmed the stability of meta-analysis. The meta-analysis suggests that OGG1 rs1052133 polymorphism is significantly associated with the risk of colorectal cancer in Caucasian population.