Single nucleotide polymorphisms of one-carbon metabolism and cancers of the esophagus, stomach, and liver in a Chinese population

Investigation of the relationship between MTRR A66G, MTR A2756G gene variations and cell anomalies in early diagnosis and progression of bladder cancer

BACKGROUND

The aim of this study is to investigate the relationship between MTRR A66G, MTRA2756G gene variations and cell anomalies in the early diagnosis and progression of bladder cancer.

METHODS

PCR and RFLP methods were used to determine the genotype distributions of MTRR A66G and MTR A2756G gene variations. Peripheral smear preparations prepared from blood samples were fixed with methanol fixative and stained histochemically. Cellular morphological evaluations were made under the light microscope.

RESULTS

In our study, AA-GG haplotype was observed significantly more in the patient group than control group (OR: 3.304, 95% CI: 1.023-10.665, p = 0.046). The significant increase was determined in terms of histological damage parameters in the patient group compared to the control group (p < 0.05). For multiple vacuoles damage parameter (mild score), AA genotype of MTR A2756G gene variation was significantly different compared to AA genotype of MTRR A66G gene variation (OR: 0.211, 0.049-0.912, p = 0.037). AA genotype of MTR A2756G gene variation was observed more than AA homozygous genotype of MTR A66G gene variation for giant platelets with different sizes damage parameter (mild score) (OR: 0.062, 0.017-0.228, p < 0.001).

CONCLUSIONS

In conclusion, in Thrace population, AA genotype of the MTR A2756G gene variation was significantly higher than the AA homozygous genotype of the MTR A66G gene variation as a genetic risk factor for the multiple vacuoles damage parameter. In addition, AA genotype of MTR A2756G gene variation was determined as a genetic risk factor for giant platelets with different sizes damage parameter.

Susceptibility of Genetic Variations in Methylation Pathway to Gastric Cancer

Background

DNA methylation in the CpG island is associated with gastric cancer, genetic variations residue in genes involved in methylation pathway could contribute to the occurrence of gastric cancer. Here, we investigated the association between DNMTs (DNMT1/DNMT3A/DNMT3B), MTHFR genetic variations and gastric cancer risk and patients' survival.

Patients and Methods

We recruited 490 gastric cancer patients and 488 age- and sex-matched healthy controls. The genotypes of the genetic variations were detected by a Mass-array platform. A commercial Helicobacter pylori (H. pylori) immunogold testing kit was used to determine the H. pylori infection.

Results

We found that carriers of DNMT1 rs2228612C allele was associated with decreased gastric cancer risk (CT vs. TT: adjusted OR = 0.70, 95% CI = 0.53-0.94, P = 0.02; CT/CC vs.TT: adjusted OR = 0.73, 95% CI = 0.56-0.96, P = 0.02). Further stratified analysis showed that DNMT1 rs2228612 CT/CC were associated with a decreased gastric cancer risk in the subgroups of age ≤64 years old (adjusted OR = 0.61, 95% CI = 0.41-0.90, P = 0.01), male (adjusted OR = 0.72, 95% CI = 0.53-0.98, P = 0.03), negative H. pylori infection (adjusted OR = 0.67, 95% CI = 0.45-0.98, P = 0.04), tumor stage T3-T4 (adjusted OR = 0.69, 95% CI = 0.51-0.92, P = 0.01), and non-gastric cardiac adenocarcinoma (NGCA) (adjusted OR = 0.72, 95% CI = 0.54-0.97, P = 0.03). However, none of the genetic variations of this study was associated with overall survival.

Conclusion

We concluded that the DNMT1 rs2228612C genotype is a protective factor for gastric cancer in Han Chinese population.

MTRR rs1532268 polymorphism and gastric cancer risk: evidence from a meta-analysis

OBJECTIVE

The methionine synthase reductase (MTRR) gene encodes the MTRR enzyme involved in the metabolic pathway of homocysteine. Several studies investigated the effect of the MTRR rs1532268 gene polymorphism on the risk of gastric cancer (GC), but the results have been inconsistent.

METHODS

We performed a comprehensive and systematic search of PubMed, Google Scholar, MEDLINE, Science Direct, Scopus, CNKI, and Web of Science. Five studies were included in this meta-analysis to determine whether MTRR rs1532268 polymorphism contributes to the risk of GC.

RESULTS

Pooled data indicated that the MTRR rs1532268 polymorphism significantly increased GC risk under the allele comparison model (odds ratio [OR] = 1.14, 95% confidence interval [CI] = 1.01-1.29) and dominant model (OR = 1.14, 95% CI = 1.00-1.30). In the analysis stratified by ethnicity, no relationship was found in Whites or Asians.

CONCLUSION

Our meta-analysis suggests a positive correlation between MTRR rs1532268 polymorphism and GC development.

Associations between methylenetetrahydrofolate reductase polymorphisms and hepatocellular carcinoma risk: An update meta-analysis and trial sequential analysis

AIM

To evaluate the associations between the methylenetetrahydrofolate reductase (MTHFR) single-nucleotide polymorphisms (SNPs) and hepatocellular carcinoma (HCC) with meta-analysis and trial sequential analysis.

METHODS

PubMed, Embase, the Google Scholar, Wan fang database, VIP database, and China National Knowledge Infrastructure were extensively searched before April 2021. Odds ratios (ORs) and 95% confidence interval (95% CI) were calculated. Review Manager Version 5.3, STATA version 12.0 and TSA 0.9.5.10 Beta software were used.

RESULTS

Nineteen studies with 6941 HCC patients and 9436 controls were finally included. The MTHFR rs1801133 (C677T) SNP was associated with increased HCC risk under heterozygote genetic model (OR = 1.10, 95% CI = [1.01, 1.20]). For Subgroup analysis, increased risks of HCC were detected in Mongoloid, Chinese. For MTHFR rs1801131 (A1298C) SNP, increased risk of HCC was only observed in Caucasians (allelic: OR = 1.86, 95% CI = [1.49, 2.31]; homozygote: OR = 3.39, 95% CI = [2.18, 5.27]), interesting decreased risk was detected in Mongoloid (recessive: OR = 0.30, 95% CI = [0.15, 0.58]; homozygote: OR = 0.41, 95% CI = [0.24, 0.72]). Sensitivity analysis indicated stability in our results. Publication bias was not detected based on Begg test and Egger test. Trial sequential analysis indicated further studies to confirm the associations in MTHFR C677T polymorphism.

CONCLUSION

The MTHFR rs1801133 SNP was associated with an increased risk of HCC in Mongoloid population especially in Chinese. Increased HCC risk is also observed in Caucasian population for the MTHFR rs1801131 SNP, and decreased risk of HCC is remarkably discovered in Mongoloid and Chinese subgroups, which need further validation.

Riboflavin intake, MTRR genetic polymorphism (rs1532268) and gastric cancer risk in a Korean population: a case-control study

The vitamin B group, including riboflavin, plays paramount roles in one-carbon metabolism (OCM), and disorders related to this pathway have been linked to cancer development. The variants of genes encoding OCM enzymes and the insufficiency of B vitamins could contribute to carcinogenesis. Very few observational studies have revealed a relationship between riboflavin and gastric cancer (GC), especially under conditions of modified genetic factors. We carried out a study examining the association of riboflavin intake and its interaction with MTRR (rs1532268) genetic variants with GC risk among 756 controls and 377 cases. The OR and 95 % CI were evaluated using unconditional logistic regression models. We observed protective effects of riboflavin intake against GC, particularly in the female subgroup (OR = 0·52, 95 % CI 0·28, 0·97, Ptrend = 0·031). In the MTRR (rs1532268) genotypes analysis, the dominant model showed that the effects of riboflavin differed between the CC and CT + TT genotypes. Compared with CC carriers, low riboflavin intake in T+ carriers was significantly associated with a 93 % higher GC risk (OR = 1·93, 95 % CI 1·09, 3·42, Pinteraction = 0·037). In general, higher riboflavin intake might help reduce the risk of GC in both CC and TC + TT carriers, particularly the T+ carriers, with marginal significance (OR = 0·54, 95 % CI 0·28, 1·02, Pinteraction = 0·037). Our study indicates a protective effect of riboflavin intake against GC. Those who carry at least one minor allele and have low riboflavin intake could modify this association to increase GC risk in the Korean population.

Methylenetetrahydrofolate reductase C677T (Ala>Val, rs1801133 C>T) polymorphism decreases the susceptibility of hepatocellular carcinoma: a meta-analysis involving 12,628 subjects

C677T (Ala>Val, rs1801133 C>T), a non-synonymous variant of methylenetetrahydrofolate reductase (MTHFR) gene, has been found to be associated with an impair enzyme activity of MTHFR. The relationship of MTHFR rs1801133 with hepatocellular carcinoma (HCC) has been extensively investigated. However, the findings were conflicting. Recently, more investigations have been conducted on the relationship of MTHFR rs1801133 with HCC. To obtain a more precise assessment on the effect of this non-synonymous variant to the development of HCC, a pooled-analysis was performed. This meta-analysis consisted of 19 independent case–control studies. By using the odds ratio (OR) combined with 95% confidence interval (CI), the relationship of MTHFR rs1801133 with HCC risk was determined. A total of 19 independent case–control studies were included. Finally, 6,102 HCC cases and 6,526 controls were recruited to examine the relationship of MTHFR rs1801133 with HCC risk. In recessive model (TT vs. CC/CT), the findings reached statistical significance (OR, 0.90; 95%CI, 0.82–0.98; P = 0.016). Subgroup analysis also found an association between MTHFR rs1801133 polymorphism and the decreased risk of HCC in hepatitis/virus related patients (recessive model: OR, 0.85; 95%CI, 0.72–0.99; P = 0.035, and allele model: OR, 0.90; 95%CI, 0.81–0.99; P = 0.028). Subgroup analyses indicated that extreme heterogeneity existed in Asian population, larger sample size investigation, hospital-based study and normal/healthy control subgroups. The shape of Begger’s seemed symmetrical. Egger’s linear regression test also confirmed these evaluations. Sensitivity analyses suggested that our findings were stable. In summary, our results highlight that MTHFR rs1801133 polymorphism decreases HCC susceptibility. The relationship warrants a further assessment.

Alcohol consumption and risk of stomach cancer: A meta-analysis

Stomach cancer is one of the most common cancers in the world. The relationship between alcohol consumption and the risk of stomach cancer remains unclear. Epidemiology studies investigating this relationship have shown inconsistent findings. A meta-analysis was performed to explore the association between alcohol consumption and increased stomach cancer risk. Eighty-one epidemiology studies, including 68 case-control studies and 13 cohort studies, were included in this study. A significant association was found between alcohol consumption and increased risk of stomach cancer (OR = 1.20, 95% CI 1.12-1.27). To explore the source of the significant heterogeneity (p < 0.05, I² = 86%), analysis was stratified by study type (case-control study and cohort study), control type (hospital-based control and population-based control), gender (male, female, and mix), race (White and Asian), region (United States, Sweden, China, Japan), subsite of stomach cancer, and type of alcohol. The stratified analyses found that region and cancer subsite are major sources of the high heterogeneity. The inconsistent results in different regions and different subsites might be related to smoking rates, Helicobacter pylori infection, obesity, and potential genetic susceptibility. The positive association between drinking and increased risk of stomach cancer is consistent in stratified analyses. The dose-response analysis showed a clear trend that a higher daily intake of alcohol is associated with a higher risk of stomach cancer.

Association Between ALDH2 Polymorphism and Gastric Cancer Risk in Terms of Alcohol Consumption: A Meta-Analysis

BACKGROUND

Alcohol may increase gastric cancer risk. Alcohol can be more carcinogenic in persons who possess inactive ALDH2. The aim of this meta-analysis was to evaluate whether ALDH2 polymorphism can affect alcohol-induced gastric carcinogenesis.

METHODS

We searched the PubMed, EMBASE, and Cochrane databases to identify relevant articles published between January 2000 and September 2019. Eligible articles were selected according to inclusion and exclusion criteria. The data were analyzed using Review Manager 5.3.

RESULTS

A total of 7 case-control studies on ALDH2 rs671 polymorphism consisting of 3,251 gastric cancer cases and 4,943 controls were included in the analysis. Inactive ALDH2 genotypes (G/A or A/A) were associated with an increased risk of gastric cancer (odds ratio [OR] = 1.26, 95% confidence interval [CI]: 1.04 to 1.52, p = 0.02, I²  = 64%), compared with active ALDH2 (G/G genotype). Subgroup analysis by alcohol consumption showed that inactive ALDH2 increased risk for gastric cancer in moderate to heavy drinkers (OR = 1.85, 95% CI: 1.52 to 2.25, p < 0.01, I² = 6%) more than in nondrinkers or mild drinkers (OR = 1.19; 95% CI: 1.05 to 1.36, p < 0.01, I²  = 6%). Moderate/heavy alcohol consumption increased gastric cancer risk in individuals with inactive ALDH2 (OR = 2.23, 95% CI: 1.63 to 3.05, p < 0.01, I² = 30%) more than those with active ALDH2 (OR = 1.40, 95% CI: 0.98 to 2.01, p = 0.07, I² = 85%).

CONCLUSIONS

The ALDH2 polymorphism modifies the risk of gastric cancer. Moderate/heavy drinkers are more susceptible to gastric cancer than non-drinkers or light drinkers with inactive ALDH2.

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.

DNMT1 and DNMT3B genetic polymorphisms affect the clinical course and outcome of melanoma patients

The aberrant DNA methylation plays a critical role in a number of different malignancies, including melanoma. DNA methylation is catalyzed by DNA methyltransferases (DNMTs), involved in methylation maintenance (DNMT1) and de novo DNA methylation (DNMT3A and DNMT3B). The current study investigated the association of genetic variants in the DNMT1 and DNMT3B with the clinicopathologic features and the clinical course of melanoma patients. In the present study, DNMT1 (rs2228612, rs2228611, and rs2114724) and DNMT3B (rs406193 and rs2424932) polymorphisms were examined in 123 melanoma patients. Single nucleotide polymorphisms were assessed using TaqMan SNPs Genotyping Assays according to the manufacturer's protocols. The carriers of the variant genotype of DNMT1 rs2228612 had poorer overall survival and recurrence-free survival, (P = 0.000 and 0.000, respectively), and an increased risk for adverse outcome [hazard ratio (HR) = 6.620, 95% confidence interval (CI): 2.214-19.791, P = 0.001]. DNMT1 rs2228612 was also associated with ulceration (P = 0.045), nodal status (P = 0.030), progression (P = 0. 007), and stage of disease (P = 0.003). Univariate analysis indicated that tumor-infiltrating lymphocytes could be a marker of good prognosis in melanoma patients (HR = 0.323, 95% CI: 0.127-0.855, P = 0.025), whereas the genotype distribution of the DNMT3B rs406193 polymorphism correlated significantly with the presence of tumor-infiltrating lymphocytes (P = 0.012). The multivariate analysis showed that the DNMT1 rs2228612 polymorphism (HR = 12.126, 95% CI: 2.345-62.715, P = 0.003) is an independent predictor of poor overall survival in melanoma patients. As expected, disease progression was also found to be an independent prognostic factor in melanoma patients (HR = 37.888, 95% CI: 3.615-397.062, P = 0.002). DNMT1 rs2228612 was found to be an independent predictor of poor overall survival in melanoma patients. DNMTs polymorphisms could serve as a potential target for novel therapeutic approaches.

Effect of ALDH2 polymorphism on cancer risk in Asians: A meta-analysis

Numerous studies have investigated the association between ALDH2 gene rs671G>A polymorphism and various cancer type in Asians. However, the results remain inconclusive.We conducted a comprehensive meta-analysis including 63 articles with 66 studies containing 25,682 cases and 47,455 controls retrieved by searching PubMed and Embase electronic databases up to March 5, 2018.Pooled results indicated that ALDH2 gene rs671 polymorphism was significantly associated with the overall cancer risk in Asians (homozygous model: odds ratio [OR] = 0.85, 95% confidence interval [CI] = 0.72-0.99, P = .042; heterozygous model: OR = 1.32, 95% CI = 1.14-1.52, P  < .001; recessive model: OR = 0.73, 95% CI = 0.60-0.88, P = .001; dominant model: OR = 1.32, 95% CI = 1.16-1.51, P < .001; and allele comparison model: OR = 1.11, 95% CI = 1.03-1.19, P = .004), especially in esophageal cancer and among the Chinese and the Japanese.Our results suggest that ALDH2 rs671 polymorphism is associated with the overall cancer risk in Asians. Well-designed prospective studies with more information about gene-environment interaction, such as drinking, should be conducted to validate our findings.

Disturbed homocysteine metabolism is associated with cancer

Hyperhomocysteinemia/Homocysteinuria is characterized by an increased level of toxic homocysteine in the plasma. The plasma concentration of homocysteine is 5–15 μmol/L in healthy individuals, while in hyperhomocysteinemic patients, it can be as high as 500 μmol/L. While increased homocysteine levels can cause symptoms such as osteoporosis and eye lens dislocation, high homocysteine levels are most closely associated with cardiovascular complications. Recent advances have shown that increased plasma Hcy is also a fundamental cause of neurodegenerative diseases (including Alzheimer’s disease, Parkinson’s disease, and dementia), diabetes, Down syndrome, and megaloblastic anemia, among others. In recent years, increased plasma homocysteine has also been shown to be closely related to cancer. In this review, we discuss the relation between elevated plasma Hcy levels and cancer, and we conclude that disturbed homocysteine metabolism is associated with cancer. Future clinical perspectives are also discussed.

Cancer can be added to the wide range of diseases known to be associated with elevated blood levels of the small amino acid homocysteine. Abnormally high levels of this compound are already known to contribute to conditions including cardiovascular problems, neurodegenerative diseases, neural tube defects, Down’s syndrome, diabetes and megaloblastic anemia. This review, by Laishram R. Singh and colleagues at the University of Delhi, India, concludes that disturbed homocysteine metabolism is associated with many forms of human cancer. The authors discuss a range of genetic, epigenetic and environmental factors that may be involved in the cause and effect relationships between homocysteine metabolism and cancer. It is particularly interesting that low folate (vitamin B9) levels result in high homocysteine levels, and vice versa. Further research may yield insights leading to new forms of cancer treatment and diagnosis.

LINE-1 and EPAS1 DNA methylation associations with high-altitude exposure

Recent discoveries indicate a genetic basis for high-altitude adaptation among human groups who have resided at high altitude for millennia, including Andeans, Tibetans, and Ethiopians. Yet, genetics alone does not explain the extent of variation in altitude-adaptive phenotypes. Current and past environments may also play a role, and one way to determine the effect of the environment is through the epigenome. To characterize if Andean adaptive responses to high altitude have an epigenetic component, we analyzed DNA methylation of the promoter region of EPAS1 and LINE-1 repetitive element among 572 Quechua individuals from high- (4,388 m) and low-altitude (0 m) in Peru. Participants recruited at high altitude had lower EPAS1 DNA methylation and higher LINE-1 methylation. Altitude of birth was associated with higher LINE-1 methylation, not with EPAS1 methylation. The number of years lived at high altitude was negatively associated with EPAS1 methylation and positively associated with LINE-1 methylation. We found four one-carbon metabolism SNPs (MTHFD1 rs2236225, TYMS rs502396, FOLH1 rs202676, GLDC rs10975681) that cumulatively explained 11.29% of the variation in average LINE-1 methylation. And identified an association between LINE-1 methylation and genome-wide SNP principal component 1 that distinguishes European from Indigenous American ancestry suggesting that European admixture decreases LINE-1 methylation. Our results indicate that both current and lifetime exposure to high-altitude hypoxia have an effect on EPAS1 and LINE-1 methylation among Andean Quechua, suggesting that epigenetic modifications may play a role in high-altitude adaptation.

Single nucleotide polymorphisms in candidate genes associated with milk yield in Argentinean Holstein and Holstein x Jersey cows

BACKGROUND

Research on loci influencing milk production traits of dairy cattle is one of the main topics of investigation in livestock. Many genomic regions and polymorphisms associated with dairy production have been reported worldwide. In this context, the purpose of this study was to identify candidate loci associated with milk yield in Argentinean dairy cattle. A database of candidate genes and single nucleotide polymorphisms (SNPs) for milk production and composition was developed. Thirty-nine SNPs belonging to 22 candidate genes were genotyped on 1643 animals (Holstein and Holstein x Jersey). The genotypes obtained were subjected to association studies considering the whole population and discriminating the population by Holstein breed percentage. Phenotypic data consisted of milk production values recorded during the first lactation of 1156 Holstein and 462 Holstein x Jersey cows from 18 dairy farms located in the central dairy area of Argentina. From these records, 305-day cumulative milk production values were predicted.

RESULTS

Eight SNPs (rs43375517, rs29004488, rs132812135, rs137651874, rs109191047, rs135164815, rs43706485, and rs41255693), located on six Bos taurus autosomes (BTA4, BTA6, BTA19, BTA20, BTA22, and BTA26), showed suggestive associations with 305-day cumulative milk production (under Benjamini-Hochberg procedure with a false discovery rate of 0.1). Two of those SNPs (rs43375517 and rs135164815) were significantly associated with milk production (Bonferroni adjusted p-values < 0.05) when considering the Holstein population.

CONCLUSIONS

The results obtained are consistent with previously reported associations in other Holstein populations. Furthermore, the SNPs found to influence bovine milk production in this study may be used as possible candidate SNPs for marker-assisted selection programs in Argentinean dairy cattle.

A single-nucleotide polymorphism (rs1805087) in the methionine synthase (METH) gene increases the risk of prostate cancer

Methionine synthase (METH, i.e., MTR) is a key enzyme in the folate pathway, which plays a critical role in the synthesis, repair, and methylation of DNA. The association between METH gene polymorphisms and prostate cancer susceptibility remains ambiguous. Thus, we performed an updated meta-analysis of METH single-nucleotide polymorphism rs1805087 involving 12 independent case-control studies comprising 9986 prostate cancer patients and 40134 controls. The odds ratio and 95% confidence intervals were applied to evaluate the relation of this single-nucleotide polymorphism with prostate cancer. Statistical analysis was performed in STATA 11.0. A significant association was found between rs1805087 and increased prostate cancer risk, overall and with Hardy-Weinberg equilibrium. In subgroup analyses (based on ethnicity, source of control, genotyping methods, or publication status), similar associations were observed (e.g., genotype GA vs. AA: odds ratio 1.19, 95% confidence interval 1.01-1.40 among whites; G allele vs. A allele: odds ratio 1.14, 95% confidence interval 1.02-1.28 among hospital-based controls). Thus, the common polymorphism (rs1805087) of METH may be associated with increased prostate cancer risk. Further studies with a larger sample size and detailed gene-environment interactions should be conducted to identify the role of METH polymorphisms in prostate cancer susceptibility.

Association of five genetic variations in DNMT1 and DNMT3A with gastric cancer in a Chinese population

AIM

To determine whether genetic variations in DNMT1 and DNMT3A could be associated with gastric cancer risk.

MATERIALS & METHODS

A total of 466 patients and 452 healthy controls were enrolled in this study. Genotypes were examined by using the Sequenom MassARRAY platform.

RESULTS

No significant differences in the distribution frequencies were observed between the groups. However, subgroup analysis revealed that, in the group aged ≤60 years, DNMT3A rs13420827 was associated with reduced gastric cancer risk, and that carrier of GC/GG genotype was associated with reduced risk of gastric cancer with low differentiation or at the T3-T4 stage.

CONCLUSION

This study suggests that five genetic variations of interest in DNMT1 and DNMT3A are not associated with the presence of gastric cancer, but that rs13420827 may contribute to the gastric cancer risk for those younger individuals, the risk of which may be influenced by the characteristics of tumor.

Alcohol-Induced Epigenetic Changes in Cancer

Chronic, heavy alcohol consumption is associated with serious negative health effects, including the development of several cancer types. One of the pathways affected by alcohol toxicity is the one-carbon metabolism. The alcohol-induced impairment of this metabolic pathway results in epigenetic changes associated with cancer development. These epigenetic changes are induced by folate deficiency and by products of the ethanol metabolism. The changes induced by long-term heavy ethanol consumption result in elevations of homocysteine and S-adenosyl-homocysteine (SAH) and reductions in S-adenosylmethionine (SAM) and antioxidant glutathione (GSH) levels, leading to abnormal promoter gene hypermethylation, global hypomethylation, and metabolic insufficiency of antioxidant defense mechanisms. In addition, reactive oxygen species (ROS) generated during the ethanol metabolism induce alterations in DNA methylation patterns that play a critical role in cancer development. Specific epigenetic changes in esophageal, hepatic, and colorectal cancers have been detected in blood samples and proposed to be used clinically as epigenetic biomarkers for diagnosis and prognosis of these cancers. Also, genetic variants of genes involved in one-carbon metabolism and ethanol metabolism were found to modulate the relationship between alcohol-induced epigenetic changes and cancer risk. Furthermore, alcohol metabolism products have been associated with an increase in NADH levels, which lead to histone modifications and changes in gene expression that in turn influence cancer susceptibility. Chronic excessive use of alcohol also affects selected members of the family of microRNAs, and as miRNAs could act as epigenetic regulators, this may play an important role in carcinogenesis. In conclusion, targeting alcohol-induced epigenetic changes in several cancer types could make available clinical tools for the diagnosis, prognosis, and treatment of these cancers, with an important role in precision medicine.

Association between ALDH2 rs671 G>A polymorphism and gastric cancer susceptibility in Eastern Asia

To date, the relationship between the aldehyde dehydrogenases-2 (ALDH2) rs671 G>A (Glu504Lys) polymorphism and gastric cancer (GC) risk has not been thoroughly elucidated. To derive a more precise estimation of the effect of the ALDH2 rs671 G>A polymorphism on GC, we conducted this meta-analysis. We searched for qualified studies in the Embase, PubMed, Wang Fan and China National Knowledge Infrastructure databases. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the association. A total of 6,421 GC patients and 8,832 control subjects were included in the present study. The pooled results indicated no significant relationship between the ALDH2 rs671 G>A polymorphism and GC susceptibility in all genetic models. A stratified analysis by country showed that the ALDH2 rs671 G>A polymorphism might be a risk factor for GC in Japan (Allele model: P_unadjusted = 0.034; Dominant model: P_unadjusted = 0.040); however, the result was nonsignificant when the Bonferroni correction and false discovery rate (FDR) were applied. In subgroup analyses by drinking status in the dominant model, our study revealed that the ALDH2 rs671 G>A polymorphism significantly increased the risk of GC for drinkers (dominant model: P < 0.001). No relationship between the ALDH2 rs671 G>A polymorphism and GC risk was observed in any other subgroup. Our present study indicated no association between the ALDH2 rs671 G>A polymorphism and GC risk in Eastern Asian populations. However, the ALDH2 rs671 G>A polymorphism can significantly increase GC risk for drinkers.

One-carbon genetic variants and the role of MTHFD1 1958G>A in liver and colon cancer risk according to global DNA methylation

Several polymorphic gene variants within one-carbon metabolism, an essential pathway for nucleotide synthesis and methylation reactions, are related to cancer risk. An aberrant DNA methylation is a common feature in cancer but whether the link between one-carbon metabolism variants and cancer occurs through an altered DNA methylation is yet unclear. Aims of the study were to evaluate the frequency of one-carbon metabolism gene variants in hepatocellular-carcinoma, cholangiocarcinoma and colon cancer, and their relationship to cancer risk together with global DNA methylation status. Genotyping for BHMT 716A>G, DHFR 19bp ins/del, MTHFD1 1958G>A, MTHFR 677C>T, MTR 2756A>G, MTRR 66A>G, RFC1 80G>A, SHMT1 1420C>T, TCII 776C>G and TS 2rpt-3rpt was performed in 102 cancer patients and 363 cancer-free subjects. Methylcytosine (mCyt) content was measured by LC/MS/MS in peripheral blood mononuclear cells (PBMCs) DNA. The MTHFD1 1958AA genotype was significantly less frequent among cancer patients as compared to controls (p = 0.007) and related to 63% reduction of overall cancer risk (p = 0.003) and 75% of colon cancer risk (p = 0.006). When considering PBMCs mCyt content, carriers of the MTHFD1 1958GG genotype showed a lower DNA methylation as compared to carriers of the A allele (p = 0.048). No differences were highlighted by evaluating a possible relationship between the other polymorphisms analyzed with cancer risk and DNA methylation.

The MTHFD1 1958AA genotype is linked to a significantly reduced cancer risk. The 1958GG genotype is associated to PBMCs DNA hypomethylation as compared to the A allele carriership that may exert a protective effect for cancer risk by preserving from DNA hypomethylation.

A Meta-Analysis of the Association between DNMT1 Polymorphisms and Cancer Risk

Previous studies have examined the associations of DNA methyltransferase 1 (DNMT1) polymorphisms, including single nucleotide polymorphisms rs16999593 (T/C), rs2228611 (G/A), and rs2228612 (A/G), with cancer risk. However, the results are inconclusive. The aim of this meta-analysis is to elucidate the associations between DNMT1 polymorphisms and cancer susceptibility. The PubMed, Embase, Web of Science, and Chinese National Knowledge Infrastructure databases were searched systematically to identify potentially eligible reports. Odd ratios and 95% confidence intervals were used to evaluate the strength of association between three DNMT1 polymorphisms and cancer risk. A total of 16 studies were finally included in the meta-analysis, namely, nine studies of 3378 cases and 4244 controls for rs16999593, 11 studies of 3643 cases and 3866 controls for rs2228611, and three studies of 1343 cases and 1309 controls for rs2228612. The DNMT1 rs2228612 (A/G) polymorphism was significantly related to cancer risk in the recessive model. The meta-analysis also suggested that DNMT1 rs16999593 (T/C) may be associated with gastric cancer, while rs2228611 (G/A) may be associated with breast cancer. In future research, large-scale and well-designed studies are required to verify these findings.

ALDH2 polymorphism and alcohol-related cancers in Asians: a public health perspective

The occurrence of more than 200 diseases, including cancer, can be attributed to alcohol drinking. The global cancer deaths attributed to alcohol-consumption rose from 243,000 in 1990 to 337,400 in 2010. In 2010, cancer deaths due to alcohol consumption accounted for 4.2% of all cancer deaths. Strong epidemiological evidence has established the causal role of alcohol in the development of various cancers, including esophageal cancer, head and neck cancer, liver cancer, breast cancer, and colorectal cancer. The evidence for the association between alcohol and other cancers is inconclusive. Because of the high prevalence of ALDH2*2 allele among East Asian populations, East Asians may be more susceptible to the carcinogenic effect of alcohol, with most evidence coming from studies of esophageal cancer and head and neck cancer, while data for other cancers are more limited. The high prevalence of ALDH2*2 allele in East Asian populations may have important public health implications and may be utilized to reduce the occurrence of alcohol-related cancers among East Asians, including: 1) Identification of individuals at high risk of developing alcohol-related cancers by screening for ALDH2 polymorphism; 2) Incorporation of ALDH2 polymorphism screening into behavioral intervention program for promoting alcohol abstinence or reducing alcohol consumption; 3) Using ALDH2 polymorphism as a prognostic indicator for alcohol-related cancers; 4) Targeting ALDH2 for chemoprevention; and 5) Setting guidelines for alcohol consumption among ALDH2 deficient individuals. Future studies should evaluate whether these strategies are effective for preventing the occurrence of alcohol-related cancers.

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.

DNMT1, DNMT3A and DNMT3B Polymorphisms Associated With Gastric Cancer Risk: A Systematic Review and Meta-analysis

BACKGROUND

Increasing studies showed that abnormal changes in single nucleotide polymorphisms (SNPs) of DNMTs (DNMT1, DNMT3A and DNMT3B) were associated with occurrence or decrease of various tumors. However, the associations between DNMTs variations and gastric cancer (GC) risk were still conflicting. We aimed to assess the effect of DNMTs polymorphisms on the susceptibility to GC.

METHODS

Firstly, we did a meta-analysis for 7 SNPs (rs16999593, rs2228611, rs8101866 in DNMT1, rs1550117, rs13420827 in DNMT3A, rs1569686, rs2424913 in DNMT3B). Four genetic models (homozygote, heterozygote, dominant and recessive model) were used. Moreover, a meta-sensitivity and subgroup analysis was performed to clarify heterogeneity source. Lastly, 17 SNPs that couldn't be meta-analyzed were presented in a systematic review.

FINDINGS

20 studies were included, 13 studies could be meta-analyzed and 7 ones could not. Firstly, a meta-analysis on 13 studies (3959 GC cases and 5992 controls) for 7 SNPs showed that GC risk increased in rs16999593 (heterozygote model: OR 1.36, 95%CI 1.14-1.61; dominant model: OR 1.36, 95%CI 1.15-1.60) and rs1550117 (homozygote model: OR 2.03, 95%CI 1.38-3.00; dominant model: OR 1.20, 95%CI 1.01-1.42; recessive model: OR 1.96, 95%CI 1.33-2.89) but decreased in rs1569686 (dominant model: OR 0.74, 95%CI 0.61-0.90). The remaining SNPs were not found associated with GC risk. Furthermore, the subgroup analysis indicated that for rs1550117 and rs1569686, the significant associations were particularly found in people from Chinese Jiangsu province (rs1550117, OR 1.77, 95%CI 1.25-2.51; rs1569686, OR 0.48, 95%CI 0.36-0.64) and that PCR-RFLP was a sensitive method to discover significant associations (rs1550117, OR 1.77, 95%CI 1.25-2.51; rs1569686, OR 0.49, 95%CI 0.37-0.65). Lastly, a systematic review on 7 studies for 17 SNPs suggested that rs36012910, rs7560488 and rs6087990 might have a potential effect on GC initiation.

CONCLUSION

This meta-analysis demonstrated that rs16999593 and rs1550117 could contribute to GC risk and that rs1569686 might be a protective factor against gastric carcinogenesis. By using these SNPs as biomarkers, it is feasible to estimate the risk of acquiring GC and thus formulate timely preventive strategy.

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.

MicroRNA-related polymorphisms and non-Hodgkin lymphoma susceptibility in the Multicenter AIDS Cohort Study

BACKGROUND

MicroRNAs, small non-coding RNAs involved in gene regulation, are implicated in lymphomagenesis. We evaluated whether genetic variations in microRNA coding regions, binding sites, or biogenesis genes (collectively referred to as miRNA-SNPs) were associated with risk of AIDS-associated non-Hodgkin lymphoma (AIDS-NHL), and serum levels of four lymphoma-related microRNAs.

METHODS

Twenty-five miRNA-SNPs were genotyped in 180 AIDS-NHL cases and 529 HIV-infected matched controls from the Multicenter AIDS Cohort Study (MACS), and real-time polymerase chain reaction was used to quantify serum microRNA levels. Adjusted odds ratios (ORs) estimated using conditional logistic regression evaluated associations between miRNA-SNPs and AIDS-NHL risk. A semi-Bayes shrinkage approach was employed to reduce likelihood of false-positive associations. Adjusted mean ratios (MR) calculated using linear regression assessed associations between miRNA-SNPs and serum microRNA levels.

RESULTS

DDX20 rs197412, a non-synonymous miRNA biogenesis gene SNP, was associated with AIDS-NHL risk (OR=1.34 per minor allele; 95% CI: 1.02-1.75), and higher miRNA-222 serum levels nearing statistical significance (MR=1.21 per minor allele; 95% CI: 0.98-1.49). MiRNA-196a2 rs11614913 was associated with decreased central nervous system (CNS) AIDS-NHL (CT vs. CC OR=0.52; 95% CI: 0.27-0.99). The minor allele of HIF1A rs2057482, which creates a miRNA-196a2 binding site, was associated with systemic AIDS-NHL risk (OR=1.73 per minor allele; 95% CI: 1.12-2.67), and decreased CNS AIDS-NHL risk (OR=0.49 per minor allele; 95% CI: 0.25-0.94).

CONCLUSIONS

This study suggests that a few miRNA-SNPs are associated with AIDS-NHL risk and may modulate miRNA expression. These results support a role for miRNA in AIDS-NHL and may highlight pathways to be targeted for risk stratification or therapeutics.

Measurement of Histone Methylation Dynamics by One-Carbon Metabolic Isotope Labeling and High-energy Collisional Dissociation Methylation Signature Ion Detection

Accumulating evidence suggests that cellular metabolites and nutrition levels control epigenetic modifications, including histone methylation. However, it is not currently possible to measure the metabolic control of histone methylation. Here we report a novel detection method to monitor methyl transfer from serine to histones through the one-carbon metabolic pathway, using stable-isotope labeling and detection of lysine methylation signature ions generated in high-energy-dissociation (HCD) tandem mass spectrometry. This method is a long-needed tool to study the metabolic control of histone methylation.

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

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

Polymorphism in one-carbon metabolism pathway affects survival of gastric cancer patients: Large and comprehensive study

Although it has been shown that polymorphisms in one-carbon metabolism (OCM) pathway are associated with gastric cancer (GC), their interactions and contributions for patients' survival are elusive. In this study, we investigated the effects of polymorphisms and their interactions on the survival of GC patients, including genes of Methylenetetrahydrofolate reductase (MTHFR 677C > T, 1298A > C), Methionine synthase reductase (MTRR 66A > G), Methionine synthase (MTR 2756A > G), and Thymidylate synthase (TS 3'-UTR ins6 > del6, 5'-UTR 2R > 3R). We recruited 919 GC patients from 1998 to 2006. The Kaplan-Meier plots, Cox regression analyses and the log-rank tests were carried out in this study. MTHFR 1298CC genotype showed protective effect (HR = 0.444, 95% CI = 0.210-0.940). MTRR 66 GA + GG genotypes decreased the risk of death (HR = 0.793, 95% CI = 0.651-0.967) in general, and in subgroups with more pronounced diffuse type, greater depth of invasion (T2/T3/T4), higher level lymph node metastasis (N1/N2/N3), advanced TNM stages (II/III level) and 5-Fu treatment. However, the improved survival disappeared when GC patients simultaneously had MTR 2756 GA + GG genotypes (HR = 1.063, 95% CI = 0.750-1.507). Although MTRR 66GA genotype was not associated with the survival of GC patients, patients with simultaneous MTRR 66GA and MTR 2756AA genotypes exhibited significant risk reduction of death (HR = 0.773, 95% CI = 0.609-0.981). MTHFR 1298 CA + CC combined with TS 5-UTR 2R3R + 3R3R genotypes (HR = 0.536, 95% CI = 0.315-0.913) also increased patient survival rates. Our results suggest that the MTRR 66A > G and MTHFR 1298A > C polymorphisms may be useful prognostic biomarkers for GC patients.

The association between RFC1 G80A polymorphism and cancer susceptibility: Evidence from 33 studies

Aberrant folate metabolism is closely related to tumorigenesis. Genetic variations in the Reduced folate carrier 1 (RFC1) may alter the progress of folate metabolism, and thereby cause the initiation and progress of the cancer. Considerable studies have performed to investigate the association between RFC1 G80A (rs1051266) polymorphism and cancer susceptibility, but the conclusions were conflicting. Therefore, we conducted a meta-analysis to reevaluate the association of RFC1 G80A polymorphism with cancer risk. PubMed and EMBASE were searched for eligible studies. The association of RFC1 G80A polymorphism and cancer risk was evaluated by the pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs). The significant association was found between RFC1 G80A polymorphism and hematological malignance susceptibility (A vs. G: OR=1.11, 95%CI=1.003-1.23, P=0.045; GA vs. GG: OR=1.18, 95%CI=1.06-1.31, P=0.002; AA+GA vs. GG: OR=1.18, 95%CI=1.07-1.29, P=0.001). Stratified analysis by ethnicity indicated that the association became more prominent among Caucasians (GA vs. GG: OR=1.28, 95%CI=1.12-1.45, P<0.001; AA+GA vs. GG: OR=1.21, 95%CI=1.08-1.36, P=0.001). In term of the cancer type, this polymorphism significantly increased the risk of acute lymphoblast leukemia (GA vs. GG: OR=1.13, 95%CI=1.001-1.28, P=0.048; AA+GA vs. GG: OR=1.28, 95%CI=1.13-1.46, P<0.001) and acute myeloid leukemia (GA vs. GG: OR=2.57, 95%CI=1.37-4.85, P=0.003). No significant association between RFC1 G80A polymorphism and overall solid cancer risk was observed, but a protective association with digestive cancer risk was found (GA vs. GG: OR=0.89, 95%CI= 0.81-0.99, P=0.030). The comprehensive meta-analysis encouraged the notion that RFC1 G80A polymorphism may play an important role in hematopoietic system malignance. These findings need further validation in the large multicenter investigations.

Simultaneous Analysis of SEPT9 Promoter Methylation Status, Micronuclei Frequency, and Folate-Related Gene Polymorphisms: The Potential for a Novel Blood-Based Colorectal Cancer Biomarker

One challenge in colorectal cancer (CRC) is identifying novel biomarkers to be introduced in screening programs. The present study investigated the promoter methylation status of the SEPT9 gene in peripheral blood samples of subjects' positive fecal occult blood test (FOBT). In order to add new insights, we investigated the association between SEPT9 promoter methylation and micronuclei frequency, and polymorphisms in the folate-related pathway genes. SEPT9 promoter methylation, micronuclei frequency, and genotypes were evaluated on 74 individuals' FOBT positive. Individuals were subjected to a colonoscopy that provided written informed consent for study participation. SEPT9 promoter methylation status was significantly lower in the CRC group than controls (p = 0.0006). In contrast, the CaCo2 cell-line, analyzed as a tissue specific model of colon adenocarcinoma, showed a significantly higher percentage of SEPT9 promoter methylation compared to the CRC group (p < 0.0001). Linear regression analysis showed an inverse correlation between micronuclei frequency and the decrease in the methylation levels of SEPT9 promoter region among CRC patients (β = -0.926, p = 0.0001). With regard to genotype analysis, we showed the involvement of the DHFR polymorphism (rs70991108) in SEPT9 promoter methylation level in CRC patients only. In particular, the presence of at least one 19 bp del allele significantly correlates with decreased SEPT9 promoter methylation, compared to the 19 bp ins/ins genotype (p = 0.007). While remaining aware of the strengths and limitations of the study, this represents the first evidence of a novel approach for the early detection of CRC, using SEPT9 promoter methylation, micronuclei frequency and genotypes, with the potential to improve CRC risk assessment.

Dietary folate, one-carbon metabolism-related genes, and gastric cancer risk in Korea

SCOPE

We evaluated the interactions between polymorphisms involved in one-carbon metabolism-related genes and dietary folate intake in gastric cancer risk within the Korean population through a hospital-based case-control study.

METHODS AND RESULTS

A total of 542 controls and 271 cases were included. Genotype data were selected from data produced by the Affymetrix Axiom(®) Exome 319 Array. We considered seven single nucleotide polymorphisms (SNPs) of five genes whose SNPs are located in the coding region with a minor allele frequency > 5%: MTHFR (G1793A, A1298C, C677T), MTR A2756G, MTRR A66G, SHMT1 C1420T, and SLC19A1 G80A. Our study found that MTR A2756G was associated with a decreased gastric cancer risk. MTHFR G1793A showed a statistically significant interaction between dietary folate intake and gastric cancer.

CONCLUSION

Our results suggest that MTR A2756G is significantly associated with gastric cancer risk, and that MTHFR G1793A statistically interacts with dietary folate intake. Our findings indicate that gene-folate interactions may contribute to gastric cancer risk.