The polymorphisms in methylenetetrahydrofolate reductase, methionine synthase, methionine synthase reductase, and the risk of colorectal cancer

Interactions between vitamin B2, the MTRR rs1801394 and MTR rs1805087 genetic polymorphisms, and colorectal cancer risk in a Korean population

OBJECTIVES

We explored whether the association between vitamin B2 and colorectal cancer (CRC) risk could be modified by the MTRR rs1801394 and MTR rs1805087 genetic polymorphisms and examined whether the interaction effects are sex-specific.

METHODS

We performed a case-control study involving 1,420 CRC patients and 2,840 controls from the Korea National Cancer Center. Dietary vitamin B2 intake was assessed using a semiquantitative food frequency questionnaire, and the association with CRC was evaluated. Genotyping was performed using an Illumina MEGA-Expanded Array. For gene-nutrient interaction analysis, pre-matched (1,081 patients and 2,025 controls) and matched (1,081 patients and 1,081 controls) subsets were included. Unconditional and conditional logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

A higher intake of vitamin B2 was associated with a significantly lower CRC risk (OR, 0.65; 95% CI, 0.51 to 0.82; p<0.001). Carriers of at least 1 minor allele of MTRR rs1801394 showed a significantly higher CRC risk (OR, 1.43; 95% CI, 1.12 to 1.83). Males homozygous for the major allele (A) of MTRR rs1801394 and who had a higher intake of vitamin B2 had a significantly lower CRC risk (OR, 0.31; 95% CI, 0.18 to 0.54; p-interaction=0.02). In MTR rs1805087, males homozygous for the major allele (A) and who had a higher vitamin B2 intake had a significantly lower CRC risk (OR, 0.38; 95% CI, 0.25 to 0.60; p-interaction<0.001).

CONCLUSIONS

The MTRR rs1801394 and MTR rs1805087 genetic polymorphisms may modify the association between vitamin B2 and CRC risk, particularly in males. However, further studies are warranted to confirm these interaction results.

Global DNA Methylation Levels Viz-a-Viz Genetic and Biochemical Variations in One Carbon Metabolic Pathway: An Exploratory Study from North India

Despite the importance of one carbon metabolic pathway (OCMP) in modulating the DNA methylation process, only a few population-based studies have explored their relationship among healthy individuals. This study aimed to understand the variations in global DNA methylation levels with respect to selected genetic (CBS 844ins68, MTRR A66G, MTR A2756G, and MTHFR C677T polymorphisms) and biochemical (folate, vitamin B12, and homocysteine) markers associated with OCMP among healthy North Indian adults. The study has been conducted among 1095 individuals of either sex (69.5% females), aged 30-75 years. A sample of 5 mL of blood was collected from each participant. Homocysteine, folate, and vitamin B12 levels were determined using the chemiluminescence technique. Restriction digestion was performed for genotyping MTRR A66G, MTR A2756G, and MTHFR C677T polymorphisms and allele-specific PCR amplification for CBS 844ins68 polymorphism. Global DNA methylation levels were analyzed using ELISA-based colorimetric technique. Of the selected genetic and biochemical markers, the mutant MTRR A66G allele was positively associated with global DNA methylation levels. Further, advanced age was inversely associated with methylation levels. MTRR 66GG genotype group was hypermethylated than other genotypes in folate replete and vitamin B12 deficient group (a condition prevalent among vegetarians), suggesting that the G allele may be more efficient than the wild-type allele in such conditions. Global DNA methylation levels appeared to be more influenced by genetic than biochemical factors. MTRR 66G allele may have a selective advantage in vitamin B12 deficient conditions. Further research should be undertaken to understand how genetics affects epigenetic processes.

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.

Genetic Variants in the Mitochondrial Thymidylate Biosynthesis Pathway Increase Colorectal Cancer Risk

We assess the contributions of genetic variants for the enzymes involved in capecitabine metabolism to colorectal cancer (CRC) development risk. In this case-control study, DNA samples were collected from 66 patients (King Abdulaziz University Hospital) and 65 controls (King Fahad General Hospital) between April and November 2022 to be used in PCR-RFLP. The chi-square (χ2) test at a significance level of p ˂ 0.05 was used to estimate genotype and allele frequencies. The Lys27Gln variant of cytidine deaminase (CDA) showed a risk ratio (RR) of 1.47 for heterozygous (AC) carriers, with genotype distributions for patients (χ2 = 1.97) and controls (χ2 = 14.7). Homozygous (AA) Ala70Thr carriers demonstrated a three-fold higher risk, with genotype distributions for patients (χ2 = 3.85) and controls (χ2 = 4.23). Genotype distributions of the 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T variant for patients were (χ2 = 22.43) and for controls were (χ2 = 0.07); for the MTHFR A1298C variant, they were (χ2 = 54.44) for patients and (χ2 = 4.58) for controls. Heterozygous (AC) carriers of the A1298C variant demonstrated highly significant protection against CRC development (RR = 0.2, p = 0.001), while a two-fold higher risk for CRC was estimated for homozygous genotype (CC) carriers. In conclusion, the heterozygous genotype of CDA Lys27Gln, the homozygous genotype of CDA Ala70Thr, and the homozygous genotype of MTHFR A1298C were associated with CRC development risk. The heterozygous genotype of MTHFR A1298C variant provided highly significant protection against CRC development. Further examinations using a larger population size are needed to reliably confirm our findings.

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.

Metabolic pathways in sporadic colorectal carcinogenesis: A new proposal

Given the reports made about geographical differences in Colorectal Cancer (CRC) occurrence, suggesting a link between dietary habits, genes and cancer risk, we hypothesise that there are four fundamental metabolic pathways involved in diet-genes interactions, directly implicated in colorectal carcinogenesis: folate metabolism; lipid metabolism; oxidative stress response; and inflammatory response. Supporting this hypothesis are the evidence given by the significant associations between several diet-genes polymorphisms and CRC, namely: MTHFR, MTR, MTRR and TS (involved in folate metabolism); NPY, APOA1, APOB, APOC3, APOE, CETP, LPL and PON1 (involved in lipid metabolism); MNSOD, SOD3, CAT, GSTP1, GSTT1 and GSTM1 (involved in oxidative stress response); and IL-1, IL-6, TNF-α, and TGF-β (involved in inflammatory response). We also highlight the association between some foods/nutrients/nutraceuticals that are important in CRC prevention or treatment and the four metabolic pathways proposed, and the recent results of genome-wide association studies, both assisting our hypothesis. Finally, we propose a new line of investigation with larger studies, using accurate dietary biomarkers and investigating the four metabolic pathways genes simultaneously. This line of investigation will be essential to understand the full complexity of the association between nature and nurture in CRC and perhaps in other types of cancers. Only with this in-depth knowledge will it be possible to make personalised nutrition recommendations for disease prevention and management.

Mendelian Randomization Study: The Association Between Metabolic Pathways and Colorectal Cancer Risk

Background: The roles of obesity-related biomarkers and their molecular pathways in the development of postmenopausal colorectal cancer (CRC) have been inconclusive. We examined insulin resistance (IR) as a major hormonal pathway mediating the association between obesity and CRC risk in a Mendelian randomization (MR) framework.

Methods: We performed MR analysis using individual-level data of 11,078 non-Hispanic white postmenopausal women from our earlier genome-wide association study. We identified four independent single-nucleotide polymorphisms associated with fasting glucose (FG), three with fasting insulin (FI), and six with homeostatic model assessment–IR (HOMA-IR), which were not associated with obesity. We estimated hazard ratios (HRs) for CRC by adjusting for potential confounding factors plus genetic principal components.

Results: Overall, we observed no direct association between combined 13 IR genetic instruments and CRC risk (HR = 0.96, 95% confidence interval [CI]: 0.78–1.17). In phenotypic analysis, genetically raised HOMA-IR exhibited its effects on the increased risk and FG and FI on the reduced risk for CRC, but with a lack of statistical power. Subgroup analyses by physical activity level and dietary fat intake with combined phenotypes showed that genetically determined IR was associated with reduced CRC risk in both physical activity-stratified (single contributor: MTRR rs722025; HR = 0.12, 95% CI: 0.02–0.62) and high-fat diet subgroups (main contributor: G6PC2 rs560887; HR = 0.59, 95% CI: 0.37–0.94).

Conclusions: Complex evidence was observed for a potential causal association between IR and CRC risk. Our findings may provide an additional value of intervention trials to lower IR and reduce CRC risk.

Polymorphisms in MTHFR, MTR, RFC1 and CßS genes involved in folate metabolism and thyroid cancer: a case-control study

INTRODUCTION

Polymorphisms in genes coding enzymes involved in folate metabolism may cause alterations in this metabolic pathway and contribute to carcinogenesis, because folate is essential for DNA synthesis, methylation and repair. The objective of this study was to investigate the association of MTHFR 677C>T (rs1801133), MTR 2756A>G (rs1805087), RFC1 80A>G (rs1051266) and CßS 844ins(68) (no rs#) polymorphisms and thyroid cancer development. The association of these polymorphisms with demographic risk factors and clinical histopathological parameters was also evaluated.

MATERIAL AND METHODS

The study is a case-control analysis with a total of 462 individuals (151 patients and 311 controls). Polymerase chain reaction-restriction fragment length polymorphism technique was used for genotyping. The χ² and multiple logistic regression were utilized for statistical analysis.

RESULTS

The polymorphisms analysis revealed an association between the MTHFR 677C>T polymorphism (OR = 2.87, 95% CI: 1.50-5.48, p < 0.01, codominant model), (OR = 1.76, 95% CI: 1.18-2.64, p < 0.01, dominant model), (OR = 2.37, 95% CI: 1.28-4.39, p < 0.01, recessive model) and thyroid cancer. RFC1 80A>G polymorphism also was associated with thyroid cancer under recessive mode of inheritance (OR = 1.55; 95% CI: 1.02-2.38; p = 0.04); however, this polymorphism showed Hardy-Weinberg disequilibrium in the control group (χ² = 24.71, p < 0.001). Furthermore, alcohol (OR = 1.56, 95% CI: 1.36-1.89, p < 0.01) and tobacco consumption (OR = 1.97, 95% CI: 1.28-3.04, p < 0.01) were associated with increased risk for thyroid cancer. The MTR 2756A>G polymorphism showed an association with tumor extent (OR = 2.69, 95% CI: 1.27-5.71, p < 0.01) and aggressiveness (OR = 4.51, 95% CI: 1.67-12.1, p < 0.01).

CONCLUSIONS

MTHFR 677C>T is significantly associated with increased risk for thyroid cancer and MTR 2756A>G is associated with tumor extent and aggressiveness. In addition, alcohol and tobacco consumption were associated with increased risk of thyroid cancer. These results may contribute to a better prognosis for thyroid cancer.

Donor one‑carbon metabolism gene single nucleotide polymorphisms predict the susceptibility of cancer recurrence after liver transplantation

BACKGROUND

Many enzymes involved in one‑carbon metabolism (OCM) are considered to have important roles in carcinogenesis, especially in hepatocellular carcinoma (HCC). However, the influence of polymorphisms in OCM genes on recurrence in HCC patients with liver transplantation has yet not been reported. The aim of this study was to explore the impact of donor liver graft OCM gene polymorphism on the prognosis of liver transplant recipients with HCC.

METHODS

This study enrolled 100 liver transplantation patients from a Chinese Han population to detect the association between donor OCM genes polymorphisms and post-transplant HCC recurrence. Nine SNPs from seven OCM genes (MTHFD1, MTR, MTRR, DHFR, ALDH1L1, SHMT1, and CBS) were evaluated by Chi-square test and Kaplan-Meier survival analysis.

RESULT

None of the nine SNPs were significantly associated with cancer recurrence after liver transplantation. However, tumor-free survival for recipients with the AA genotype of rs1801394 polymorphism was significantly shorter than patients with AG/GG genotype (1097 ± 155 vs. 1657 ± 173 days, P < 0.05) among patients with alpha-fetoprotein < 400 ng/ml. Kaplan-Meier survival curves showed that recipients with donor rs1127717 homozygous TT had a significantly longer tumor-free survival and overall survival than heterozygous CT/CC recipients (tumor-free survival 1395 ± 128 vs. 671 ± 233 days, P < 0.05; overall survival 1540 ± 114 vs. 925 ± 242 days, P < 0.05) in the patient subgroup with well or moderately differentiated HCC.

CONCLUSION

This is the first genetic study to examine the relation between donor liver graft OCM gene polymorphisms and the risk of HCC recurrence after liver transplantation. Our findings support the hypothesis that polymorphisms of donor genes related to OCM play important roles in post-transplant HCC recurrence. Furthermore, donor rs1801394 and rs1127717 polymorphism may serve as promising prognostic biomarkers for HCC recurrence in liver transplant recipients.

Gene-Metabolite Interaction in the One Carbon Metabolism Pathway: Predictors of Colorectal Cancer in Multi-Ethnic Families

For personalized healthcare, the purpose of this study was to examine the key genes and metabolites in the one-carbon metabolism (OCM) pathway and their interactions as predictors of colorectal cancer (CRC) in multi-ethnic families. In this proof-of-concept study, we included a total of 30 participants, 15 CRC cases and 15 matched family/friends representing major ethnic groups in southern California. Analytics based on supervised machine learning were applied, with the target variable being specified as cancer, including the ensemble method and generalized regression (GR) prediction. Elastic Net with Akaike's Information Criterion with correction (AICc) and Leave-One-Out cross validation GR methods were used to validate the results for enhanced optimality, prediction, and reproducibility. The results revealed that despite some family members sharing genetic heritage, the CRC group had greater combined gene polymorphism-mutations than the family controls (p < 0.1) for five genes including MTHFR C677T, MTHFR A1298C, MTR A2756G, MTRR A66G, and DHFR 19bp. Blood metabolites including homocysteine (7 µmol/L), methyl-folate (40 nmol/L) with total gene mutations (≥4); age (51 years) and vegetable intake (2 cups), and interactions of gene mutations and methylmalonic acid (MMA) (400 nmol/L) were significant predictors (all p < 0.0001) using the AICc. The results were validated by a 3% misclassification rate, AICc of 26, and >99% area under the receiver operating characteristic curve. These results point to the important roles of blood metabolites as potential markers in the prevention of CRC. Future intervention studies can be designed to target the ways to mitigate the enzyme-metabolite deficiencies in the OCM pathway to prevent cancer.

Personalized Nutrition-Genes, Diet, and Related Interactive Parameters as Predictors of Cancer in Multiethnic Colorectal Cancer Families

To personalize nutrition, the purpose of this study was to examine five key genes in the folate metabolism pathway, and dietary parameters and related interactive parameters as predictors of colorectal cancer (CRC) by measuring the healthy eating index (HEI) in multiethnic families. The five genes included methylenetetrahydrofolate reductase (MTHFR) 677 and 1298, methionine synthase (MTR) 2756, methionine synthase reductase (MTRR 66), and dihydrofolate reductase (DHFR) 19bp, and they were used to compute a total gene mutation score. We included 53 families, 53 CRC patients and 53 paired family friend members of diverse population groups in Southern California. We measured multidimensional data using the ensemble bootstrap forest method to identify variables of importance within domains of genetic, demographic, and dietary parameters to achieve dimension reduction. We then constructed predictive generalized regression (GR) modeling with a supervised machine learning validation procedure with the target variable (cancer status) being specified to validate the results to allow enhanced prediction and reproducibility. The results showed that the CRC group had increased total gene mutation scores compared to the family members (p < 0.05). Using the Akaike’s information criterion and Leave-One-Out cross validation GR methods, the HEI was interactive with thiamine (vitamin B1), which is a new finding for the literature. The natural food sources for thiamine include whole grains, legumes, and some meats and fish which HEI scoring included as part of healthy portions (versus limiting portions on salt, saturated fat and empty calories). Additional predictors included age, as well as gender and the interaction of MTHFR 677 with overweight status (measured by body mass index) in predicting CRC, with the cancer group having more men and overweight cases. The HEI score was significant when split at the median score of 77 into greater or less scores, confirmed through the machine-learning recursive tree method and predictive modeling, although an HEI score of greater than 80 is the US national standard set value for a good diet. The HEI and healthy eating are modifiable factors for healthy living in relation to dietary parameters and cancer prevention, and they can be used for personalized nutrition in the precision-based healthcare era.

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.

Gene Environment Interactions and Predictors of Colorectal Cancer in Family-Based, Multi-Ethnic Groups

For the personalization of polygenic/omics-based health care, the purpose of this study was to examine the gene-environment interactions and predictors of colorectal cancer (CRC) by including five key genes in the one-carbon metabolism pathways. In this proof-of-concept study, we included a total of 54 families and 108 participants, 54 CRC cases and 54 matched family friends representing four major racial ethnic groups in southern California (White, Asian, Hispanics, and Black). We used three phases of data analytics, including exploratory, family-based analyses adjusting for the dependence within the family for sharing genetic heritage, the ensemble method, and generalized regression models for predictive modeling with a machine learning validation procedure to validate the results for enhanced prediction and reproducibility. The results revealed that despite the family members sharing genetic heritage, the CRC group had greater combined gene polymorphism rates than the family controls (p < 0.05), on MTHFR C677T, MTR A2756G, MTRR A66G, and DHFR 19 bp except MTHFR A1298C. Four racial groups presented different polymorphism rates for four genes (all p < 0.05) except MTHFR A1298C. Following the ensemble method, the most influential factors were identified, and the best predictive models were generated by using the generalized regression models, with Akaike's information criterion and leave-one-out cross validation methods. Body mass index (BMI) and gender were consistent predictors of CRC for both models when individual genes versus total polymorphism counts were used, and alcohol use was interactive with BMI status. Body mass index status was also interactive with both gender and MTHFR C677T gene polymorphism, and the exposure to environmental pollutants was an additional predictor. These results point to the important roles of environmental and modifiable factors in relation to gene-environment interactions in the prevention of CRC.

Correlation between global methylation level of peripheral blood leukocytes and serum C reactive protein level modified by MTHFR polymorphism: a cross-sectional study

BACKGROUND

Chronic inflammatory conditions are associated with higher tumor incidence through epigenetic and genetic alterations. Here, we focused on an association between an inflammation marker, C-reactive-protein (CRP), and global DNA methylation levels of peripheral blood leukocytes.

METHODS

The subjects were 384 healthy Japanese women enrolled as the control group of a case-control study for breast cancer conducted from 2001 to 2005. Global DNA methylation was quantified by Luminometric Methylation Assay (LUMA).

RESULTS

With adjustment for lifestyle-related factors, including folate intake, the global DNA methylation level of peripheral blood leukocytes was significantly but weakly increased by 0.43% per quartile category for CRP (P for trend = 0.010). Estimated methylation levels stratified by CRP quartile were 70.0%, 70.8%, 71.4%, and 71.3%, respectively. In addition, interaction between polymorphism of MTHFR (rs1801133, known as C677T) and CRP was significant (P for interaction = 0.046); the global methylation level was significantly increased by 0.61% per quartile category for CRP in the CT/TT group (those with the minor allele T, P for trend = 0.001), whereas no association was observed in the CC group (wild type).

CONCLUSIONS

Our study suggests that CRP concentration is weakly associated with global DNA methylation level. However, this association was observed more clearly in individuals with the minor allele of the MTHFR missense SNP rs1801133. By elucidating the complex mechanism of the regulation of DNA methylation by both acquired and genetic factors, our results may be important for cancer prevention.

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.

MTRR rs1801394 and its interaction with MTHFR rs1801133 in colorectal cancer: a case-control study and meta-analysis

AIM

This study aims to evaluate the association between the MTRR rs1801394 alone or in interaction with the MTHFR rs1801133 and susceptibility to colorectal cancer (CRC) and its characteristics in Iranian population. Additionally, both a systematic review and meta-analysis were performed to derive a more precise assessment of this association.

MATERIALS & METHODS

Genomic DNA of 2332 subjects was genotyped for rs1801394. These data were pooled with 17 eligible studies for meta-analysis.

RESULTS

No significant association was found between the rs1801394 or rs1801394-rs1801133 and CRC risk. Meta-analysis results also demonstrated no significant relationship between the rs1801394 and CRC risk.

CONCLUSION

Results of this study showed that the rs1801394 alone or together with the rs1801133 is not a risk factor for CRC in Iranian population.

Association of Three Single Nucleotide Polymorphisms in MTR and MTRR Genes with Lung Cancer in a Turkish Population

AIMS

Folate metabolism plays a critical role in DNA methylation and synthesis. Polymorphisms in folate metabolism may affect enzyme activities and thereby affect the cancer risk. Methionine synthase (MTR) and methionine synthase reductase (MTRR) are critical enzymes for the folate cycle. In this study, possible associations between genetic variabilities in MTR and MTRR and susceptibility to lung cancer (LC) were investigated in a Turkish population.

METHODS

A case-control study with 193 LC cases and 199 noncancerous controls was conducted. DNA was extracted from leukocytes using the high pure polymerase chain reaction (PCR) template preparation kit. The MTR 2756 A>G (rs1805087), MTRR 524 C > T (rs1532268), and MTRR 66 A>G (rs1801394) genotypes were determined using PCR-restriction fragment length polymorphism (PCR-RFLP) assays. The genotype and haplotype analyses of these polymorphisms were performed using SPSS 21 and Haploview 4.2, respectively.

RESULTS

An association between the MTRR A66G polymorphism and LC (p = 0.042) was found. In addition, this allele was observed more frequently in smokers compared to nonsmokers (p = 0.030). In contrast, the distribution of the MTR 2756 A>G and the MTRR 524 C > T allele frequencies were similar in the subject cases and controls.

CONCLUSIONS

In conclusion, the present study suggests an association between the MTRR 66 A>G gene polymorphisms and LC risk in a Turkish population.

The MTHFR C677T mutation is not a risk factor recognized for HBV-related HCC in a population with a high prevalence of this genetic marker

BACKGROUND

Polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene can affect disease progression in HBV infection. However, the results from different reports are inconsistent. The aim of this study was to investigate the association between the MTHFR C677T polymorphism and the outcome of HBV infection in a Tianjin Han population.

METHODS

TaqMan SNP genotyping was employed to determine the alleles and genotypes of MTHFR C677T in 2511 subjects from various stages of HBV infection and 549 healthy controls.

RESULTS

Of the 3060 subjects, the genotypic frequencies were CT 48.9%, TT 29.3% and CC 21.8%; the allelic frequencies were T 53.8% and C 46.2%. There was no significant difference in genotypic or allelic distribution among the different disease groups. When either healthy subjects or self-limited subjects were used as controls, the TT genotype and the T allele conferred protective effects against hepatocellular carcinoma (HCC) (HCC vs healthy subjects: OR=0.588, 95% CI=0.413-0.836, P=0.003; OR=0.768, 95% CI=0.645-0.915, P=0.003, respectively. HCC vs self-limited subjects: OR=0.598, 95% CI=0.404-0.886, P=0.010; OR=0.772, 95% CI=0.635-0.940, P=0.010, respectively). After sub-stratification by gender, the prevalence of the TT genotype or T allele was the lowest in the male HCC group (TT 23.5%, T 49.8%). The protective effects of the TT genotype and the T allele were observed in male HCC and cirrhotic subjects (HCC vs self-limited subjects: OR=0.470, 95% CI=0.288-0.766, P=0.002; OR=0.681, 95% CI=0.535-0.866, P=0.002, respectively. Liver cirrhosis vs self-limited subjects: OR=0.624, 95% CI=0.392-0.992, P=0.046; OR=0.791, 95% CI=0.627-0.998, P=0.048, respectively), but not in female. When the subjects were stratified according to the clinical features, no statistically significant difference in the genotypic distribution was observed (P>0.05).

CONCLUSIONS

The TT genotype and T allele of MTHFR C677T may confer a protective effect on disease progression to HCC in HBV-infected individuals, especially among male patients, in a population with a high prevalence of this genetic marker.

Association of MTRR A66G polymorphism with cancer susceptibility: Evidence from 85 studies

Methionine synthase reductase (MTRR) is a key regulatory enzyme involved in the folate metabolic pathway. Previous studies investigating the association of MTRR A66G polymorphism with cancer susceptibility reported inconclusive results. We performed the current meta-analysis to obtain a more precise estimation of the possible association. Published literatures were identified from PubMed, Embase and CBM databases up to October 2016. The strength of the association between the MTRR A66G polymorphism and cancer susceptibility was assessed using odds ratios (ORs) and the corresponding 95% confidence intervals (CIs). Eighty five published studies with 32,272 cases and 37,427 controls were included in this meta-analysis. Pooled results indicated that the MTRR A66G polymorphism was associated with an increased overall cancer risk (homozygous model: OR = 1.08, 95% CI = 1.02-1.15, P = 0.009; recessive model: OR = 1.06, 95% CI = 1.00-1.12, P < 0.001 and allele comparison: OR = 1.03, 95% CI = 1.00-1.06, P < 0.001). Stratification analysis further indicated significant associations in head and neck cancer, Caucasians, Africans, and high quality studies. However, to avoid the "false-positive report", the significant findings were assessed by the false-positive report probability (FPRP) test. Interestingly, the results of FPRP test revealed that the increased risk for MTRR A66G polymorphism among Africans need further validation due to the high probabilities of false-positive results. This meta-analysis suggests that the MTRR A66G polymorphism is associated with significantly increased cancer risk, a finding that needs to be confirmed in single large studies.

Functional variants of the 5-methyltetrahydrofolate-homocysteine methyltransferase gene significantly increase susceptibility to prostate cancer: Results from an ethnic Han Chinese population

Aberrant DNA methylation has been implicated in prostate carcinogenesis. The one-carbon metabolism pathway and related metabolites determine cellular DNA methylation and thus is thought to play a pivotal role in PCa occurrence. This study aimed to investigate the contribution of genetic variants in one-carbon metabolism genes to prostate cancer (PCa) risk and the underlying biological mechanisms. In this hospital-based case-control study of 1817 PCa cases and 2026 cancer-free controls, we genotyped six polymorphisms in three one-carbon metabolism genes and assessed their association with the risk of PCa. We found two noncoding MTR variants, rs28372871 T > G and rs1131450 G > A, were independently associated with a significantly increased risk of PCa. The rs28372871 GG genotype (adjusted OR = 1.40, P = 0.004) and rs1131450 AA genotype (adjusted OR = 1.64, P = 0.007) exhibited 1.40-fold and 1.64-fold higher risk of PCa, respectively, compared with their respective homozygous wild-type genotypes. Further functional analyses revealed these two variants contribute to reducing MTR expression, elevating homocysteine and SAH levels, reducing methionine and SAM levels, increasing SAH/SAM ratio, and promoting the invasion of PCa cells in vitro. Collectively, our data suggest regulatory variants of the MTR gene significantly increase the PCa risk via decreasing methylation potential. These findings provide a novel molecular mechanism for the prostate carcinogenesis.

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.

Polymorphisms of folate metabolism genes in patients with cirrhosis and hepatocellular carcinoma

AIM

To evaluated the association of the risk factors and polymorphisms in MTHFR C677T, MTHFR A1298C, MTR A2756G and MTRR A66G genes.

METHODS

Patients with cirrhosis (n = 116), hepatocellular carcinoma (HCC) (n = 71) and controls (n = 356) were included. Polymerase chain reaction followed by enzymatic digestion and allelic discrimination technique real-time PCR techniques were used for analysis. MINITAB-14.0 and SNPstats were utilized for statistical analysis.

RESULTS

Showed that age ≥ 46 years (OR = 10.31; 95%CI: 5.66-18.76; P < 0.001) and smoking (OR = 0.47; 95%CI: 0.28-0.78; P = 0.003) were associated with cirrhosis. Age ≥ 46 years (OR = 16.36; 95%CI: 6.68-40.05; P < 0.001) and alcohol habit (OR = 2.01; 95%CI: 1.03-3.89; P = 0.039) were associated with HCC. MTHFR A1298C in codominant model (OR = 3.37; 95%CI: 1.52-7.50; P = 0.014), recessive model (OR = 3.04; 95%CI: 1.43-6.47; P = 0.0051) and additive model (OR = 1.71; 95%CI: 1.16-2.52; P = 0.0072) was associated with HCC, as well as MTR A2756G in the additive model (OR = 1.68; 95%CI: 1.01-2.77; P = 0.047), and MTRR A66G in the codominant model (OR = 3.26; 95%CI: 1.54-6.87; P < 0.001), dominant model (OR = 2.55; 95%CI: 1.24-5.25; P = 0.007) and overdominant model (OR = 3.05; 95%CI: 1.66-5.62; P < 0.001). MTR A2756G in the additive model (OR = 1.54; 95%CI: 1.02-2.33; P = 0.042) and smokers who presented at least one polymorphic allele for MTRR A66G (OR = 1.71; 95%CI: 0.77-3.82; P = 0.0051) showed increased risk for cirrhosis. There was no association between clinical parameters and polymorphisms.

CONCLUSION

Age ≥ 46 years, alcohol habit and MTR A2756G, MTHFR A1298C and MTRR A66G polymorphisms are associated with an increased risk of HCC development; age ≥ 46 years, tobacco habit and the MTR A2756G polymorphism are associated with cirrhosis.

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.

Associations of the A66G Methionine Synthase Reductase Polymorphism in Colorectal Cancer: A Systematic Review and Meta-Analysis

Inconsistency in the reported associations between the A66G polymorphism in the methionine synthase reductase (MTRR) gene and colorectal cancer (CRC) prompted a meta-analysis, so that we could obtain a more precise estimate. Databases searches of the published literature yielded 20 case–control studies from 17 articles (8,371 cases and 12,574 controls). We calculated pooled odds ratios (ORs) and 95% confidence intervals in three genetic comparisons (A allele, G allele, and A/G genotype). We found no evidence of overall associations between MTRR A66G and CRC risk (OR 0.96–1.05, P = 0.12–0.44). This was materially unchanged when reanalyzed without the Hardy–Weinberg equilibrium (HWE)-deviating studies (OR 0.97–1.06, P = 0.11–0.65). In the A allele comparison, however, outlier treatment generated significant protection (OR 0.91, P = 0.01). Combined removal of the outliers and HWE-deviating studies reflected this summary effect (OR 0.90, P = 0.01) as did the pooled OR from high-quality studies (OR 0.90, P = 0.01). Only the Asian subgroup showed significant (both at P = 0.05) A allele (OR 1.13) and A/G genotype (OR 0.88) associations. In conclusion, post-outlier A allele effects were protective. Our study also suggests ethnic-specific associations with Asian susceptibility and protection in the A allele and A/G genotype comparisons, respectively. Folate status showed no association of this polymorphism with CRC.

Quantitative assessment of the association between MS gene polymorphism and colorectal cancer risk

Accumulating genetic association studies have investigated the risk of colorectal cancer (CRC) in relation to MS gene polymorphism with uncertain conclusions. In the current study, we sought to assess the association between MS gene and CRC. We performed an updated meta-analysis including 18 case-control studies with a total of 10, 303 CRC patients and 15, 389 CRC-free controls to estimate the strength of the association using odds ratios with the corresponding 95 % confidence intervals. Overall, no CRC risk associated with the genotypes of MS gene polymorphism was indicated in our meta-analysis. Similarly, the stratified analysis according to ethnicity and control source did not show any evident association either. The results of our updated meta-analysis suggest that MS gene polymorphism may not serve as a biomarker for the CRC risk. Future large-scale and well-designed studies are required to clarify the association identified in the present meta-analysis.

Gene polymorphisms as risk factors for predicting the cardiovascular manifestations in Marfan syndrome. Role of folic acid metabolism enzyme gene polymorphisms in Marfan syndrome

Folic acid metabolism enzyme polymorphisms are believed to be responsible for the elevation of homocysteine (HCY) concentration in the blood plasma, correlating with the pathogenesis of aortic aneurysms and aortic dissection. We studied 71 Marfan patients divided into groups based on the severity of cardiovascular involvement: no intervention required (n=27, Group A); mild involvement requiring intervention (n=17, Group B); severe involvement (n=27, Group C) subdivided into aortic dilatation (n=14, Group C1) and aortic dissection (n=13, Group C2), as well as 117 control subjects. We evaluated HCY, folate, vitamin B12 and the polymorphisms of methylenetetrahydrofolate reductase (MTHFR;c.665C>T and c.1286A>C), methionine synthase (MTR;c.2756A>G) and methionine synthase reductase (MTRR;c.66A>G). Multiple comparisons showed significantly higher levels of HCY in Group C2 compared to Groups A, B, C1 and control group (p<0.0001, p<0.0001, p=0.001 and p=0.003, respectively). Folate was lower in Group C2 than in Groups A, B, C1 and control subjects (p<0.0001, p=0.02, p<0.0001 and p<0.0001, respectively). Group C2 had the highest prevalence of homozygotes for all four gene polymorphisms. Multivariate logistic regression analysis revealed that HCY plasma level was an independent risk factor for severe cardiovascular involvement (Group C; odds ratio [OR] 1.85, 95% confidence interval [CI] 1.28-2.67, p=0.001) as well as for aortic dissection (Group C2; OR 2.49, 95%CI 1.30-4.78, p=0.006). In conclusion, severe cardiovascular involvement in Marfan patients, and especially aortic dissection, is associated with higher HCY plasma levels and prevalence of homozygous genotypes of folic acid metabolism enzymes than mild or no cardiovascular involvement. These results suggest that impaired folic acid metabolism has an important role in the development and remodelling of the extracellular matrix of the aorta.

Folic acid in pregnancy and mortality from cancer and cardiovascular disease: further follow-up of the Aberdeen folic acid supplementation trial

Background

Supplemental periconceptional folic acid is recommended to reduce the risk of fetal neural tube defects. A previous report indicated an elevated risk of breast cancer and all cancer deaths in later life among women randomised by alternate allocation to high-dose (5 mg/day) folic acid in pregnancy compared with placebo; however, findings were based on small numbers of cases. Our aim was to extend the previous analysis by including data from an additional 10 years of follow-up.

Methods

Records of participants in a large (n=2928) trial of folate supplementation (5 or 0.2 mg folic acid, or placebo) in pregnancy in the 1960s were linked to central registries in Scotland. Unadjusted and adjusted HRs were calculated for all-cause, cardiovascular, all cancer and breast cancer mortality, and all cancer and breast cancer morbidity. Analyses were done using (1) data from the time of the previous linkage (2002) to March 2013; and (2) data from 1980 to March 2013.

Results

There was no evidence to suggest an excess risk of morbidity or mortality in either supplementation group compared with placebo for 2002–2013 and no associations were seen for the full time period (1980–2013).

Conclusions

Findings from this extended follow-up do not support our previous observation of an elevated risk of mortality from breast cancer or all cancers in later life among women who had taken 5 mg folic acid/day during pregnancy. Furthermore, there were no associations with risk of mortality from all-causes, all cancers or cardiovascular disease.

Application of artificial neural networks to link genetic and environmental factors to DNA methylation in colorectal cancer

AIMS

We applied artificial neural networks (ANNs) to understand the connections among polymorphisms of genes involved in folate metabolism, clinico-pathological features and promoter methylation levels of MLH1, APC, CDKN2A(INK4A), MGMT and RASSF1A in 83 sporadic colorectal cancer (CRC) tissues, and to link dietary and lifestyle factors with gene promoter methylation.

MATERIALS & METHODS

Promoter methylation was assessed by means of methylation-sensitive high-resolution melting and genotyping by PCR-RFLP technique. Data were analyzed with the Auto Contractive Map, a special kind of ANN able to define the strength of the association of each variable with all the others and to visually show the map of the main connections.

RESULTS

We observed a strong connection between the low methylation levels of the five CRC genes and the MTR 2756AA genotype. Several other connections were revealed, including those between dietary and lifestyle factors and the methylation levels of CRC genes.

CONCLUSION

ANNs revealed the complexity of the interconnections among factors linked to DNA methylation in CRC.

Geographical and ethnic distribution of single nucleotide polymorphisms within genes of the folate/homocysteine pathway metabolism

High levels of plasma homocysteine are associated with an increased risk of many health conditions influenced by both environmental and genetic factors. The objective of this study was to provide the geographical distribution of folate pathway genetic polymorphisms in Mexico and the comparison with the reported frequencies in different continental populations. This study included the analysis of the genotypic frequencies of eight polymorphisms in genes of the folate/homocysteine metabolic pathway in 1,350 Mestizo and Amerindian subjects from different regions in Mexico and 836 individuals from European, African and Asian populations of the 1,000 Genomes Project. In Mexican Mestizo and Amerindian populations, the MTHFR C677T risk genotype (TT) was highly prevalent (frequency: 25 and 57 %, respectively). In Mestizos, the frequency showed clear regional variation related to ancestry; the Guerrero subpopulation with the highest Amerindian contribution had the highest TT frequency (33 %). The MTHFD1 G1958A AA risk genotype was also enriched in Mexican Mestizos and Amerindians (frequency: 34 and 58 %, respectively), whereas in African and Asian ancestry populations the frequency for AA was low (~4 %). All together risk genotypes showed regional differences, and Sonora had significantly different genetic frequencies compared with the other regions (P value <0.05). Our study illustrates differential geographical distribution of the risk variants in the folate/homocysteine metabolic pathway relative to ethnic background. This work supports that certain areas of the world have increased needs for folic acid and vitamin B supplementation, and this information needs to be considered in public health guidelines and eventually policies.

5,10-Methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTRR), and methionine synthase reductase (MTR) gene polymorphisms and adult meningioma risk

The causes of meningiomas are not well understood. Folate metabolism gene polymorphisms have been shown to be associated with various human cancers. It is still controversial and ambiguous between the functional polymorphisms of folate metabolism genes 5,10-methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTRR), and methionine synthase reductase (MTR) and risk of adult meningioma. A population-based case–control study involving 600 meningioma patients (World Health Organization [WHO] Grade I, 391 cases; WHO Grade II, 167 cases; WHO Grade III, 42 cases) and 600 controls was done for the MTHFR C677T and A1298C, MTRR A66G, and MTR A2756G variants in Chinese Han population. The folate metabolism gene polymorphisms were determined by using a polymerase chain reaction–restriction fragment length polymorphism assay. Meningioma cases had a significantly lower frequency of MTHFR 677 TT genotype [odds ratio (OR) = 0.49, 95 % confidence interval (CI) 0.33–0.74; P = 0.001] and T allele (OR = 0.80, 95 % CI 0.67–0.95; P = 0.01) than controls. A significant association between risk of meningioma and MTRR 66 GG (OR = 1.41, 95 % CI 1.02–1.96; P = 0.04) was also observed. When stratifying by the WHO grade of meningioma, no association was found. Our study suggested that MTHFR C677T and MTRR A66G variants may affect the risk of adult meningioma in Chinese Han population.

How folate metabolism affects colorectal cancer development and treatment; a story of heterogeneity and pleiotropy

Folate was identified as an essential micronutrient early in the twentieth century and anti-folate chemotherapy such as 5-fluorouracil (5-FU) has been central to the medical management of solid tumours including colorectal cancer for more than five decades. In the intervening years, evidence has been gathered which shows that folate deficiency leads to many human diseases throughout the life-course. However, we still do not know all of the mechanisms behind functional folate deficiency, or indeed its rescue through supplementation with natural and particularly synthetic folates. There is growing evidence that one adverse effect of folic acid fortification programmes is an increased risk of colorectal cancer within populations. The complexity of folate-dependent, one-carbon metabolism and the heterogeneity that exists between individuals with respect to the enzymes involved in the anabolic pathways, and the catabolism of 5-FU, are explored in this review. The enzyme products of some genes such as MTHFR exert multiple and perhaps unrelated effects on many phenotypes, including cancer development. We describe this pleiotropy and the common genetic variants that affect folate metabolism; and discuss some of the studies that have investigated their potential as predictive biomarkers.

Associations of variants in MTHFR and MTRR genes with male infertility in the Jordanian population

Folate pathway is expected to play an important role in spermatogenesis since it is involved in DNA synthesis, repair and methylation. The purpose of this study was to examine the association between male infertility and the MTHFR (C677T and A1298C) and MTRR (A66G) polymorphisms. A group of 300 males was recruited in this study from different Jordanian infertility clinics. Of these, 150 cases of infertile men that included oligozoospermia cases (n=45), severe oligozoospermia (n=71) and azoospermia (n=34) were studied. The other 150 males were age matched fertile controls. Genotyping of MTHFR and MTRR polymorphisms was performed using PCR-RFLP technique. The results showed an association between MTHFR 677TT genotype and male infertility (P<0.05). However, the distribution of MTHFR A1298C and MTRR A66G genotypes were not different between the fertile and infertile groups (P>0.05). In addition, none of the examined polymorphisms was related to any of the semen parameters in the infertile group. In conclusion, this study showed that MTHFR C677T polymorphism is associated with male infertility in Jordanians.

Design, synthesis, and enzyme kinetics of novel benzimidazole and quinoxaline derivatives as methionine synthase inhibitors

Methionine synthase catalyzes the transfer of a methyl group from 5-methyltetrahydrofolate to homocysteine, producing methionine and tetrahydrofolate. Benzimidazole and deazatetrahydrofolates derivatives have been shown to inhibit methionine synthase by competing with the substrate 5-methyltetrahydrofolate. In this study, a novel series of substituted benzimidazoles and quinoxalines were designed and assessed for inhibitory activity against purified rat liver methionine synthase using a radiometric enzyme assay. Compounds 3g, 3j, and 5c showed the highest activity against methionine synthase (IC₅₀: 20 μM, 18 μM, 9 μM, respectively). Kinetic analysis of these compounds using Lineweaver-Burk plots revealed characteristics of mixed inhibition for 3g and 5c; and uncompetitive inhibition for 3j. Docking study into a homology model of the rat methionine synthase gave insights into the molecular determinants of the activity of this class of compounds. The identification of these drug-like inhibitors could lead the design of the next generation modulators of methionine synthase.

Lack of association between methionine synthase A2756G polymorphism and digestive system cancer risk: evidence from 3,9327 subjects

Background

Polymorphisms in genes involved in the metabolism of folate and methyl groups have been implicated with risk of digestive system cancer. Methionine synthase (MTR) plays a central role in folate metabolism, thereby affecting DNA methylation. The association between A2756G polymorphism (rs1805087) in MTR and digestive system cancer susceptibility was inconsistent in previous studies. To investigate this inconsistency, we performed this meta-analysis.

Methods

Databases including Pubmed, EMBASE, ISI Web of Science and China National Knowledge Infrastructure (CNKI) were searched to find relevant studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association. Potential sources of heterogeneity were also assessed by subgroup analysis and meta-regression.

Results

A total of 29 articles with 15,368 patients and 23,959 controls were included. We found no association between MTR A2756G polymorphism and digestive system cancer in overall population (G allele: OR = 1.03, 95% CI = 0.98–1.09, P = 0.25; dominant model: OR = 1.03, 95% CI = 0.97–1.10, P = 0.33; recessive model: OR = 1.02, 95% CI = 0.89–1.17, P = 0.79). In the stratified analyses according to cancer type, sample size and genotyping method, no evidence of any gene-disease association was obtained in almost all genetic models. However, marginal significant associations were found for East Asians and hospital-based studies.

Conclusions

This meta-analysis suggests that there is no significant association between the MTR A2756G polymorphism and digestive system cancer risk.

Redox regulation of the epigenetic landscape in cancer: a role for metabolic reprogramming in remodeling the epigenome

Cancer arises from normal cells that acquire a series of molecular changes; however, the founding events that create the clonogens from which a tumor will arise and progress have been the subject of speculation. Through the efforts of several generations of cancer biologists it has been established that the malignant phenotype is an amalgamation of genetic and metabolic alterations. Numerous theories have suggested that either, or both, of these elements might serve as the impetus for cancer formation. Recently, the epigenetic origins of cancer have been suggested as an additional mechanism giving rise to the malignant phenotype. When the discovery that the enzymes responsible for initiating and perpetuating epigenetic events is linked to metabolism by their cofactors, a new paradigm for the origins of cancer can be created. Here, we summarize the foundation of such a paradigm on the origins of cancer, in which metabolic alterations create an epigenetic progenitor that clonally expands to become cancer. We suggest that metabolic alterations disrupt the production and availability of cofactors such as S-adenosylmethionine, α-ketoglutarate, NAD(+), and acetyl-CoA to modify the epigenotype of cells. We further speculate that redox biology can change epigenetic events through oxidation of enzymes and alterations in metabolic cofactors that affect epigenetic events such as DNA methylation. Combined, these metabolic and redox changes serve as the foundation for altering the epigenotype of normal cells and creating the epigenetic progenitor of cancer.