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

One-carbon metabolism biomarkers and upper gastrointestinal cancer in the Golestan Cohort Study

Incidence of esophageal and gastric cancer has been linked to low B-vitamin status. We conducted matched nested case-control studies of incident esophageal squamous cell carcinoma (ESCC; 340 case-control pairs) and gastric cancer (GC; 352 case-control pairs) within the Golestan Cohort Study. The primary exposure was plasma biomarkers: riboflavin and flavin mononucleotide (FMN) (vitamin B2), pyridoxal phosphate (PLP) (B6), cobalamin (B12), para-aminobenzoylglutamate (pABG) (folate), and total homocysteine (tHcy); and indicators for deficiency: 3-hydroxykyurenine-ratio (HK-r for vitamin B6) and methylmalonic acid (MMA for B12). We estimated odds ratios (ORs) and 95% confidence intervals (CIs) using conditional logistic regression adjusting for matching factors and potential confounders. High proportions of participants had low B-vitamin and high tHcy levels. None of the measured vitamin B levels was associated with the risk of ESCC and GC, but elevated level of MMA was marginally associated with ESCC (OR = 1.42, 95% CI = 0.99-2.04) and associated with GC (OR = 1.53, 95% CI = 1.05-2.22). Risk of GC was higher for the highest versus lowest quartile of HK-r (OR = 1.95, 95%CI = 1.19-3.21) and for elevated versus non-elevated HK-r level (OR = 1.59, 95% CI = 1.13-2.25). Risk of ESCC (OR = 2.81, 95% CI = 1.54-5.13) and gastric cancer (OR = 2.09, 95%CI = 1.17-3.73) was higher for the highest versus lowest quartile of tHcy. In conclusion, insufficient vitamin B12 was associated with higher risk of ESCC and GC, and insufficient vitamin B6 status was associated with higher risk of GC in this population with prevalent low plasma B-vitamin status. Higher level of tHcy, a global indicator of OCM function, was associated with higher risk of ESCC and GC.

MTHFR polymorphisms and vitamin B12 deficiency: correlation between mthfr polymorphisms and clinical and laboratory findings

Vitamin B12 deficiency is a common condition that causes a variety of disorders ranging from the development of megaloblastic anemia to the building up of neurological damage. Historically one of the leading causes of B12 deficiency appears to be secondary to malabsorption in part caused by the development of atrophic gastritis in pernicious anemia. More recently B12 deficiency could also depend on dietary restrictions. Cobalamin deficiency also appears to be closely related to folate metabolism, causing a reduction in methionine synthase activity. This results in the accumulation of 5-methyltetrahydrofolate (5-MTHF) and defective DNA synthesis. It has been hypothesized that reduced activity of the enzyme methylene-tetrahydrofolate reductase (MTHFR) could reduce the production of 5-MTHF, thereby shifting folate metabolism to thymidylate synthesis and promoting proper DNA synthesis. Our aim was to investigate the role of the C677T and A1298C MTHFR gene polymorphisms, which are associated with reduced enzyme activity, in predisposing to the development of anemia, neurological symptoms, and atrophic gastritis in a population of 105 consecutive Italian patients with cobalamin deficiency. We found statistically significant correlations between the degree of anemia and thrombocytopenia and the C677T MTHFR polymorphism, while hemoglobin levels alone significantly correlated with A1298C polymorphism, contradicting the potential protective role of these polymorphisms. Furthermore, in patients with atrophic gastritis, we found an association between the absence of parietal cell antibodies and the presence of the C677T polymorphism in homozygosity. Our results suggest a role for MTHFR enzyme activity in the severity of hematologic manifestations of vitamin B12 deficiency and as an independent mechanism of predisposition to the development of atrophic gastritis.

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

BACKGROUND AND PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Vitamin B12-Multifaceted In Vivo Functions and In Vitro Applications

Vitamin B12 plays a key role in DNA stability. Research indicates that vitamin B12 deficiency leads to indirect DNA damage, and vitamin B12 supplementation may reverse this effect. Vitamin B12 acts as a cofactor for enzymes such as methionine synthase and methylmalonyl-CoA mutase, which are involved in DNA methylation and nucleotide synthesis. These processes are essential for DNA replication and transcription, and any impairment can result in genetic instability. In addition, vitamin B12 has antioxidant properties that help protect DNA from damage caused by reactive oxygen species. This protection is achieved by scavenging free radicals and reducing oxidative stress. In addition to their protective functions, cobalamins can also generate DNA-damaging radicals in vitro that can be useful in scientific research. Research is also being conducted on the use of vitamin B12 in medicine as vectors for xenobiotics. In summary, vitamin B12 is an essential micronutrient that plays a vital role in DNA stability. It acts as a cofactor for enzymes involved in the synthesis of nucleotides, has antioxidant properties and has potential value as a generator of DNA-damaging radicals and drug transporters.

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

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

High cobalamin levels as a five-year risk predictor for developing hematological cancer

BACKGROUND

A high cobalamin level has been related to non-malignant diseases (mainly liver diseases, alcoholism, and renal diseases) and cancer (hematological malignancies and solid cancers such as liver and stomach cancer). However, a previous high level of cobalamin and the implications in the possible development of cancer is still unclear. The main aim of this study was to describe if a previous high cobalamin level is a determinant in the future development of cancer in five years of follow-up. The secondary objective was to determine any differences between cancer groups.

METHODS

A retrospective study was performed. Two databases were employed. The first one included all patients who had a determination of cobalamin in a routine blood test during the year 2010 (a total of 44,166 patients). The second one showed every patient who was admitted to the reference hospital, Hospital Clinico Universitario de Valladolid, during the following five years. Finally, a number of 6710 patients was included. Both databases belong to the medical records of the Hospital Data Surveillance System and are completely validated. Multivariate logistic regression analyses were employed to evaluate the association between cobalamin levels and the appearance of cancer (total and in each subgroup). All analyses were performed using IBM SPSS 24 software (IBM Corp., Armonk, NY, USA).

RESULTS

The sample studied showed a clear association between the risk of hematological cancer and a previous high Cbl level. This relationship was higher among patients with the highest levels (over 779 pmol/L), showing almost two times more risk for development of hematological malignance within 5 years in the multivariate analysis (OR: 1.975, 95% CI: 1.056-3.697, P=0.033). Hematological malignancies were mostly diagnosed within the first three years (86.6%), showing a similar percentage in those three years. There was no association between this previous level and the development of any other type of cancer.

CONCLUSIONS

Our study shows that a high cobalamin plasma level (hypervitaminosis) is associated with the development of hematologic cancer within five years after the measurement. The clinical implication of these findings, together with the clinical suspicion, reinforces the necessity of carrying out specific screening hematological tests in patients with not justified elevated plasma cobalamin levels. New prospective and multicenter studies are necessary to validate these results.

Association between Vitamin B12 and Risk of Gastric Cancer: A Systematic Review and Meta-Analysis of Epidemiological Studies

Epidemiological studies focusing on the association between vitamin B₁₂ and gastric cancer risk reported inconsistent findings. We conducted a systematic review and meta-analysis to assess the relationship. PubMed (Medline), Web of science and EMBASE databases were systematically searched. A total of nine studies involving 3,494 cases of with gastric cancer and 611,638 participants were included. The result showed that there is no significant association between vitamin B₁₂ intake and the risk of gastric cancer (OR = 0.88, 95% CI: 0.69-1.12, P = 0.303). Nevertheless, high intake of vitamin B₁₂ might decrease the risk of gastric cancer in Helicobacter pylori (Hp)-negative people (OR = 0.83, 95% CI: 0.62-0.99, P = 0.044), but increase the cancer risk in Hp-positive populations (OR = 1.66, 95% CI: 1.27-2.16, P = 10^-4). Additionally, further analysis indicated that excessive vitamin B₁₂ might increase the risk of non-cardia gastric cancer (OR = 1.15, 95% CI: 1.01-1.33, P = 0.006). A negative association between vitamin B₁₂ intake and gastric cancer risk was found in nonsmokers (OR = 0.83, 95% CI: 0.71-0.96, P = 0.012) but not in smokers (OR = 1.08, 95% CI: 0.71-1.47, P = 0.619). In conclusion, although we found no convincing evidence that vitamin B₁₂ intake is associated with the risk of gastric cancer, it is important to maintain the relative stability of vitamin B₁₂ for people with Hp infection.

Comparison of body condition score and other minimally invasive biomarkers between dogs with gastric carcinoma and dogs with chronic gastritis

OBJECTIVE To identify minimally invasive biomarkers to help differentiate dogs with gastric carcinoma from those with chronic gastritis. DESIGN Prospective study. ANIMALS 15 dogs with gastric carcinoma, 29 dogs with chronic gastritis, and 7 healthy dogs. PROCEDURES Dogs with clinical signs of upper gastrointestinal tract disease for > 14 days that underwent gastroscopy or necropsy for collection of gastric biopsy specimens for histologic evaluation were prospectively enrolled. Gastric carcinoma and chronic gastritis were diagnosed on the basis of histologic findings. Additionally, gastric biopsy specimens were collected endoscopically from 7 healthy (control) dogs while they were anesthetized for a routine neutering procedure. Prior to being anesthetized for gastroscopy or euthanized, all dogs underwent a physical examination, and a blood sample was collected for quantification of select serum biomarker concentrations. Histologic findings, body condition score (BCS), and serum biomarker concentrations were compared among the 3 groups. RESULTS Dogs with gastric carcinoma were significantly older and had a significantly lower BCS, lower serum folate concentration, and greater serum C-reactive protein (CRP) concentration, compared with dogs with chronic gastritis and control dogs. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that age > 8 years, BCS < 4, serum CRP concentration > 25 mg/L, and an abnormally low serum folate concentration might be useful noninvasive biomarkers for identification of dogs with gastric carcinoma. For underweight older dogs with signs of upper gastrointestinal tract disease and high serum CRP and low serum folate concentrations, gastric biopsy specimens should be obtained and evaluated so that a prompt definitive diagnosis can be made and appropriate treatment initiated.

Genetic Association of Plasma Homocysteine Levels with Gastric Cancer Risk: A Two-Sample Mendelian Randomization Study

BACKGROUND

The association of plasma homocysteine level (PHL) with gastric cancer risk was reported in observational studies. However, the causality is challenging due to confounding factors and the lack of evidence from well-designed cohort studies. Herein, we performed a two-sample Mendelian randomization (MR) analysis to investigate whether PHL is causally related to gastric cancer risk.

METHODS

We performed the MR analysis based on the results from genome-wide association studies consisting of 2,631 patients with gastric cancer and 4,373 controls. An externally weighted genetic risk score (wGRS) was constructed with 15 SNPs with well-established associations with PHL. We utilized logistic regression model to estimate associations of PHL-related SNPs and wGRS with gastric cancer risk in total population and in strata by sex, age, and study site, in addition to a series of sensitivity analyses.

RESULTS

High genetically predicted PHL was associated with an increased gastric cancer risk (per SD increase in the wGRS: OR = 1.07; 95% confidence interval, 1.01-1.12; P = 0.011), which was consistent in sensitivity analyses. Subgroup analyses provided evidence of a stronger association with gastric cancer risk in women than in men. MR-Egger and weighted median regression suggested that potentially unknown pleiotropic effects were not biasing the association between PHL and gastric cancer risk.

CONCLUSIONS

These results revealed that genetically predicted high PHL was associated with an increased gastric cancer risk, suggesting that high PHL may have a causal role in the etiology of gastric cancer.

IMPACT

These findings provide causal inference for PHL on gastric cancer risk, suggesting a causal role of high PHL in the etiology of gastric cancer.

Homocysteine and Digestive Tract Cancer Risk: A Dose-Response Meta-Analysis

Background

Homocysteine, a key component in one-carbon metabolism, is of great importance in remethylation. Many epidemiologic studies have assessed the association between homocysteine and risk of digestive tract cancer, but the results are inconsistent.

Objective

The objective of our meta-analysis is to assess the association between homocysteine and digestive tract cancer risk.

Methods

Comprehensive searches were performed on the PubMed, Embase, Cochrane, and Web of Science databases up to September 25, 2018, to identify relevant studies. Thirteen studies were included in the meta-analysis. Odds ratios (ORs) and their corresponding 95% confidence intervals (95% CIs) were used to estimate the strength of the relationship between homocysteine and the risk of digestive tract cancer.

Results

The pooled OR of digestive tract cancer risk for patients with the highest categories of blood homocysteine levels versus the lowest categories was 1.27 (95% CI, 1.15, 1.39) with no significant heterogeneity observed (P = 0.798, I ² = 0.0%). Moreover, the dose-response analysis revealed that each 5μmol/L increase in homocysteine increased the incidence of digestive tract cancer by 7%.

Conclusion

Generally, our results indicated that elevated homocysteine was associated with higher risk of digestive tract cancer. That is, homocysteine concentration may be a potential biomarker for occurrence of digestive tract cancer.

Low vitamin B12 increases risk of gastric cancer: A prospective study of one-carbon metabolism nutrients and risk of upper gastrointestinal tract cancer

Previous studies have found associations between one-carbon metabolism nutrients and risk of several cancers, but little is known regarding upper gastrointestinal tract (UGI) cancer. We analyzed prediagnostic serum concentrations of several one-carbon metabolism nutrients (vitamin B12, folate, vitamin B6, riboflavin and homocysteine) in a nested case-control study within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study of male smokers, which was undertaken in Finland between 1985 and 1988. We conducted a nested case-control study including 127 noncardia gastric adenocarcinoma (NCGA), 41 esophagogastric junctional adenocarcinoma and 60 esophageal squamous cell carcinoma incident cases identified within ATBC. Controls were matched to cases on age, date of serum collection and follow-up time. One-carbon nutrient concentrations were measured in fasting serum samples collected at baseline (up to 17 years prior to cancer diagnosis). Odds ratios and 95% confidence intervals (CI) were calculated using conditional logistic regression. Lower prediagnostic vitamin B12 concentrations at baseline were associated with a 5.8-fold increased risk of NCGA (95% CI = 2.7-12.6 for lowest compared to highest quartile, p-trend <0.001). This association remained in participants who developed cancer more than 10 years after blood collection, and after restricting the analysis to participants with clinically normal serum vitamin B12 (>300 pmol/L). In contrast, pepsinogen I, a known serologic marker of gastric atrophy, was not associated with NCGA in this population. As vitamin B12 absorption requires intact gastric mucosa to produce acid and intrinsic factor, our findings suggest vitamin B12 as a possible serologic marker for the atrophic gastritis that precedes NCGA, one more strongly associated with subsequent NCGA than pepsinogen.

Associations between dietary folate intake and risks of esophageal, gastric and pancreatic cancers: an overall and dose-response meta-analysis

There are still some controversies on the association between dietary folate intake and the risk of upper gastrointestinal cancers including esophageal, gastric and pancreatic cancers. Hence, a comprehensive meta-analysis on all available literatures was performed to clarify the relationship between dietary folate intake and risks of upper gastrointestinal cancers. An electric search was performed up to December 12^th, 2016 within the PubMed, MEDLINE AND EMBASE databases. Ultimately, a total of 46 studies which evaluated the association between folate intake and risks of upper gastrointestinal cancers were included. According to the data from included studies, the pooled results showed significant association between folate intake and esophageal (OR = 0.545, 95%CI = 0.432-0.658), gastric (OR=0.762, 95%CI=0.648-0.876) and pancreatic (OR=0.731, 95%CI=0.555-0.907) cancers. Linearity dose-response analysis indicated that with 100μg/day increment in dietary folate intake, the risk of esophageal, gastric and pancreatic cancers would decrease by 9%, 1.5% and 6%, respectively. These findings indicated that higher level of dietary folate intake could help for preventing upper gastrointestinal cancers including esophageal, gastric and pancreatic cancers.

Involvement of genetic factors and lifestyle on the occurrence of colorectal and gastric cancer

Gastrointestinal cancers are diseases due to genetic and environmental factors. In this present work we are interested in the influence of environmental factors on the occurrence of gastrointestinal cancers in Tunisian population. We found that the MTHFR C677T polymorphism was associated with colorectal cancer (P<0.04) but not with gastric cancer. In addition, we have shown that alcohol is associated with an increased risk of colorectal cancer, but the consumption of cheese is protective. Furthermore, we studied tymidylate synthase gene involved in folate metabolism. Indeed, we observed that the 5'UTR repeat polymorphism, is associated with risk of colorectal cancer, and the LL genotype (3R/3R) was significantly frequent in patients with colorectal cancer compared to controls (p=0.002; OR=2.7, 95% CI=1.4-5.2). While we found that SL genotype (2R/3R) was associated with risk of gastric cancer (p=0.015; OR=4.46, 95% CI=1.08-19-64). This polymorphism was also shown to be a predictor of response to chemotherapy based 5'-fluorouracil. However, we are interested in studying the GPX -1 gene involved in phase I metabolism of xenobiotics. We therefore evaluated the risk of TT genotype in GPX-1 C599T polymorphism with the onset of gastric cancer (P=0.0001; OR=5.41, 95% CI 1.98 to 15.58) and colorectal cancer (P=0.00008; OR=4.40, 95% CI 1.93 to 10.27). To clarify the possible relationship between environmental factors and the occurrence of the disease, we studied the additive effect of risk genotype and behavior in order to highlight the interaction of gene-environment factors.

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.

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.

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

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

Genetic modifiers of folate, vitamin B-12, and homocysteine status in a cross-sectional study of the Canadian population

BACKGROUND

Genetic variation can cause variable responses to environmental stimuli. A number of single-nucleotide polymorphisms (SNPs) have been associated with B vitamin status or chronic diseases related to vitamin B-12 and folate metabolism.

OBJECTIVE

Our objective was to identify associations between common SNPs in genes related to folate and vitamin B-12 metabolism or associated with B vitamin-related chronic diseases and biomarkers of nutrient status in a population exposed to folic acid fortification.

DESIGN

A panel of 116 SNPs was sequenced by using the Sequenom iPLEX Gold platform in a sample of 3114 adults aged 20-79 y from the Canadian Health Measures Survey, cycle 1. Associations between these SNPs and red blood cell (RBC) folate, serum vitamin B-12, and plasma total homocysteine were determined.

RESULTS

Twenty-one SNPs and 6 haplotype blocks were associated with RBC folate, serum vitamin B-12, and/or plasma homocysteine concentrations. Vitamin status was associated mainly with SNPs in genes directly involved in vitamin absorption/uptake (CUBN, CD320), transport (TCN1, TCN2), or metabolism (BHMT2, CBS, MTHFR, MUT, SHMT1). Other SNPs included those in the DNMT2, DPEP1, FUT2, NOX4, and PON1 genes.

CONCLUSIONS

We identified novel associations between SNPs in CD320 and DNMT2, which had been previously associated with neural tube defects, and vitamin B-12 status, as well as between SNPs in SHMT1, which had been previously associated with colorectal cancer and cardiovascular disease risk, and RBC folate status. These novel associations provide a plausible metabolic rationale for the association of these SNPs with B vitamin-related diseases. We also observed a novel association between an SNP in CUBN with RBC folate and confirmed the association of a number of SNPs with B vitamin status in this large cross-sectional study.

Lower folate levels in gastric cancer: Is it a cause or a result?

Folate deficiency and its association with cancer have been studied in the literature, but its clinical impact is still unknown. Folate deficiency and its result on gastric cancer is a mysterious part of oncology, with ongoing studies hopefully clarifying its impact on gastric cancer management. Lee et al studied folate deficiency and its impact on staging and clinical results. Here we try to contribute to the field by expressing our own thoughts about the paper.

The association between circulating total folate and folate vitamers with overall survival after postmenopausal breast cancer diagnosis

We studied the relationship between plasma total folate and folate vitamer concentrations [5-methyltetrahydrofolic acid, pteroylglutamic acid (folic acid) and tetrahydrofolic acid] with overall survival after breast cancer diagnosis. A secondary aim was to assess the relationship between folic acid supplement use with circulating total folate and folate vitamer concentrations. Participants were postmenopausal women diagnosed with breast cancer (n = 498) with an average follow-up of 6.7 yr. Plasma total folate and folate vitamers were measured by isotope-dilution LC-MS/MS in samples collected at or postdiagnosis. Cox proportional multivariate hazards models (controlled for stage, age at diagnosis, body mass index, parity, hormone replacement therapy use, treatment, alcohol use, folic acid use, and energy intake), were used to assess overall survival after breast cancer diagnosis. We found that the relative risk of dying for women with plasma total folate concentrations in the highest quartile was 59% lower (hazard ratio: 0.41, 95% confidence interval: 0.19-0.90) compared with the lowest quartile. Data on supplement use showed that women taking folic acid supplements had significantly higher circulating total folate and folate vitamer concentrations (P < 0.0001), suggesting that increased folate consumption through diet and/or supplementation may improve prognosis after breast cancer diagnosis.

Methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and gastric cancer susceptibility

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

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

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

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

Approaches for the identification of genetic modifiers of nutrient dependent phenotypes: examples from folate

By combining the sciences of nutrition, bioinformatics, genomics, population genetics, and epidemiology, nutrigenomics is improving our understanding of how diet and nutrient intake can interact with or modify gene expression and disease risk. In this review, we explore various approaches to examine gene–nutrient interactions and the modifying role of nutrient consumption, as they relate to nutrient status and disease risk in human populations. Two common approaches include the use of SNPs in candidate genes to identify their association with nutritional status or disease outcomes, or genome-wide association studies to identify genetic polymorphisms associated with a given phenotype. Here, we examine the results of various gene–nutrient interaction studies, the association of genetic polymorphisms with disease expression, and the identification of nutritional factors that modify gene-dependent disease phenotypes. We have focused on specific examples from investigations of the interactions of folate, B-vitamin consumption, and polymorphisms in the genes of B-vitamin dependent enzymes and their association with disease risk, followed by an examination of the strengths and limitations of the methods employed. We also present suggestions for future studies, including an approach from an on-going large scale study, to examine the interaction of nutrient intake and genotypic variation and their impact on nutritional status.

MTHFR C677T polymorphism contributes to the risk for gastric cancer

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

One-carbon metabolism dietary factors and distal gastric cancer risk in chinese women

BACKGROUND

Previous studies on the association between one-carbon dietary factors and gastric cancer risk have been inconsistent.

METHODS

We investigated this association using data from a prospective study, the Shanghai Women's Health Study (1997-2010), including 323 distal gastric cancer cases identified from 73,009 Chinese women. HRs and 95% confidence intervals (CI) were estimated using Cox proportional hazard regression after adjusting for confounders.

RESULTS

Overall, no statistically significant association of gastric cancer was observed with dietary intake of folate, methionine, or B vitamins. However, when stratified by menopausal status, higher intake of riboflavin was associated with decreased gastric cancer risk in premenopausal women with HR of 0.35 (95% CI, 0.17-0.73), 0.48 (0.24-0.97), 0.28 (0.12-0.65), and 0.23 (0.07-0.91), respectively, for the quintiles 2 to 5 intake groups compared with the lowest quintile intake (P for trend = 0.02). Among premenopausal women, highest intake of folate was associated with increased gastric cancer risk (HR, 2.62; 95% CI, 1.04-6.59). There were no statistically significant associations observed among postmenopausal women.

CONCLUSIONS

These results suggest that dietary factors involved in one-carbon metabolism are associated with gastric cancer risk among premenopausal women.

IMPACT

Riboflavin may be a protective factor and folate may be a risk factor for premenopausal gastric cancer.

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

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

Folate intake and the risk of upper gastrointestinal cancers: a systematic review and meta-analysis

BACKGROUND AND AIM

There is conflicting evidence on the association between folate intake and the risk of upper gastrointestinal tract cancers. In order to further elucidate this relationship, we performed a systematic review and quantitative meta-analysis of folate intake and the risk of esophageal, gastric, and pancreatic cancer.

METHODS

Four electronic databases (Medline, PubMed, Embase, and Current Contents Connect) were searched to July 26, 2013, with no language restrictions for observational studies that measured folate intake and the risk of esophageal cancer, gastric cancer, or pancreatic cancer. Pooled odds ratios and 95% confidence intervals were calculated using a random effects model.

RESULTS

The meta-analysis of dietary folate and esophageal cancer risk comprising of nine retrospective studies showed a decreased risk of esophageal cancer (odds ratio [OR] 0.59; 95% confidence interval [95% CI] 0.51-0.69). The meta-analysis of dietary folate and gastric cancer risk comprising of 16 studies showed no association (OR 0.94; 95% CI 0.78-1.14). The meta-analysis of dietary folate and pancreatic cancer risk comprising of eight studies showed a decreased risk of pancreatic cancer (OR 0.66; 95% CI 0.49-0.89).

CONCLUSION

Dietary folate intake is associated with a decreased risk of esophageal and pancreatic cancer, but not gastric cancer. Interpretation of these relationships is complicated by significant heterogeneity between studies when pooled, and by small numbers of studies available to analyze when stratification is performed to reduce heterogeneity.

Elevated plasma vitamin B12 levels as a marker for cancer: a population-based cohort study

BACKGROUND

A substantial proportion of patients referred for plasma vitamin B12 (cobalamin [Cbl]) measurement present with high Cbl levels, which have been reported in patients with different cancer types. However, the cancer risk among patients with newly diagnosed high Cbl levels has not been adequately examined.

METHODS

We conducted this cohort study using population-based Danish medical registries. Patients referred for Cbl measurement with levels greater than the lower reference limit (≥200 pmol/L) were identified from the population of Northern Denmark during the period of 1998 to 2009 using a database of laboratory test results covering the entire population. Data on cancer incidence (follow-up 1998-2010), Cbl treatment, and prior diagnoses were obtained from medical registries. Patients receiving Cbl treatment were excluded. Cancer risks were calculated as standardized incidence ratios (SIRs) with 95% confidence intervals (CIs), stratified by plasma Cbl levels. All statistical tests were two-sided.

RESULTS

We identified 333 667 persons without prevalent cancer and not receiving Cbl treatment. Six percent had Cbl levels greater than the upper reference limit (≥601 pmol/L). Cancer risk increased with higher Cbl levels and was highest during the first year of follow-up (Cbl 601-800 pmol/L: SIR = 3.44, 95% CI = 3.14 to 3.76; Cbl >800 pmol/L: SIR = 6.27, 95% CI = 5.70 to 6.88; both P < .001). The risks were particularly elevated for hematological and smoking- and alcohol-related cancers for persons with high Cbl levels.

CONCLUSIONS

High Cbl levels were associated with the risk of subsequently diagnosed cancer, mostly within the first year of follow-up. This may have clinical implications for the interpretation of high Cbl levels.

Unexpected high plasma cobalamin : proposal for a diagnostic strategy

It is well-established that more than 8% of patients examined for vitamin B12 deficiency unexpectedly have increased plasma levels of the vitamin, but so far there are no guidelines for the clinical interpretation of such findings. In this review, we summarise known associations between high plasma cobalamin and diseases. We report associations mainly with cancer, liver and kidney diseases, but also with a number of other diagnostic entities. The pathogenic background is poorly understood and is likely to be multi-factorial, involving increased concentrations of one or both of the circulating cobalamin binding proteins, transcobalamin and haptocorrin. Based on current knowledge, we suggest a strategy for the clinical interpretation of unexpected high plasma cobalamin. Since a number of the associated diseases are critical and life-threatening, the strategy promotes the concept of 'think the worst first'. It is important to realise that high cobalamin levels can be an unspecific marker for cancer. If this can be ruled out, diseases of the liver and kidney should be considered.

The polymorphism of methylenetetrahydrofolate reductase C677T but not A1298C contributes to gastric cancer

Increasing epidemiological studies have revealed the important role of methylenetetrahydrofolate reductase (MTHFR) in carcinogenesis. The association of MTHFR A1298C and MTHFR C677T polymorphisms with the risk for gastric cancer remains obscure due to inconsistent findings in independent studies among diverse ethnicities. A meta-analysis based on all available publications on this genetic association was performed. The pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated to estimate the effect of MTHFR variants on gastric carcinogenesis. Totally, 25 eligible case-control studies were included into the meta-analysis according to the inclusion criteria. The MTHFR C677T polymorphism was demonstrated to significantly increase the susceptibility to gastric cancer (OR(T vs. C) = 1.21, 95% CI 1.10-1.34; OR(TT vs. CC )= 1.47, 95% CI 1.22-1.76; OR(TC vs. CC )= 1.20, 95% CI 1.03-1.40; OR(TT + TC vs. CC) = 1.27, 95% CI 1.10-1.47; OR(TT vs. CC + TC )= 1.29, 95% CI 1.15-1.46), whereas no significant correlation was observed when assessing the MTHFR A1298C polymorphism (OR(C vs. A )= 1.00, 95% CI 0.90-1.10; OR(CC vs. AA) = 0.99, 95% CI 0.75-1.31; OR(CA vs. AA )= 1.01, 95% CI 0.89-1.14; OR(CC + CA vs. AA) = 1.00, 95% CI 0.89-1.13; OR(CC vs. AA + CA) = 0.97, 95% CI 0.74-1.27). Subgroup analyses by ethnicity and source of controls further confirmed the findings in overall analysis. The meta-analysis suggests that the polymorphism of MTHFR C677T but not MTHFR A1298C confers a risk effect on the development of gastric cancer among Asians and Caucasians, which provides a new insight into the gastric cancer pathogenesis.

Association Study between Folate Pathway Gene Single Nucleotide Polymorphisms and Gastric Cancer in Koreans

Gastric cancer is ranked as the most common cancer in Koreans. A recent molecular biological study about the folate pathway gene revealed the correlation with a couple of cancer types. In the folate pathway, several genes are involved, including methylenetetrahydrofolate reductase (MTHFR), methyltetrahydrofolate-homocysteine methyltransferase reductase (MTRR), and methyltetrahydrofolate-homocysteine methyltransferase (MTR). The MTHFR gene has been reported several times for the correlation with gastric cancer risk. However, the association of the MTRR or MTR gene has not been reported to date. In this study, we investigated the association between the single nucleotide polymorphisms (SNPs) of the MTHFR, MTRR, and MTR genes and the risk of gastric cancer in Koreans. To identify the genetic association with gastric cancer, we selected 17 SNPs sites in folate pathway-associated genes of MTHFR, MTR, and MTRR and tested in 1,261 gastric cancer patients and 375 healthy controls. By genotype analysis, estimating odds ratios and 95% confidence intervals (CI), rs1801394 in the MTRR gene showed increased risk for gastric cacner, with statistical significance both in the codominant model (odds ratio [OR], 1.39; 95% CI, 1.04 to 1.85) and dominant model (OR, 1.34; 95% CI, 1.02 to 1.75). Especially, in the obese group (body mass index ≥ 25 kg/m²), the codominant (OR, 9.08; 95% CI, 1.01 to 94.59) and recessive model (OR, 3.72; 95% CI, 0.92 to 16.59) showed dramatically increased risk (p < 0.05). In conclusion, rs1801394 in the MTRR gene is associated with gastric cancer risk, and its functional significance need to be validated.

Methylenetetrahydrofolate reductase C677T gene polymorphism and colorectal cancer risk: A case-control study

We designed a case-control study to determine the plasma homocysteine (Hcy) level and evaluate the potential role of the methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism in colorectal cancer (CRC). Total Hcy was quantified using the fluorescence polarization immunoassay (FPIA) on the IMx analyzer. Genomic DNA was analyzed by the real-time polymerase chain reaction (RT-PCR). The plasma levels of Hcy in the CRC group (12.63±3.11 μmol/l) were significantly higher compared with those in the control group (10.87±2.42 μmol/l; P<0.05). The frequency of the MTHFR 677TT genotype in CRC patients was markedly high. The MTHFR 677TT genotype was significantly correlated with an increased risk of CRC (odds ratio, 1.671; 95% confidence interval, 1.094-2.553; P=0.018). This study suggests that the MTHFR C677T polymorphism indicates susceptibility to CRC and is correlated with CRC pathogenesis, suggesting that the homozygous variant MTHFR C677T polymorphism is a candidate risk factor for CRC.

Folic acid increases global DNA methylation and reduces inflammation to prevent Helicobacter-associated gastric cancer in mice

BACKGROUND & AIMS

Previous studies have suggested that dietary folic acid (FA) can protect against certain types of cancers. However, the findings have varied, and the mechanisms by which FA exerts chemopreventive effects remain to be clarified. We examined the effects of FA supplementation on DNA methylation, gene expression, and gastric dysplasia in a transgenic mouse model that is etiologically and histologically well matched with human gastric cancers.

METHODS

Hypergastrinemic mice infected with Helicobacter felis were studied at multiple stages of gastric dysplasia and early cancer with FA supplementation initiated both at weaning and later in life. Global DNA methylation was assessed by a methylation sensitive cytosine incorporation assay, bisulfite pyrosequencing of B1 repetitive elements, and immunohistochemistry with anti-5-methylcytosine. We also profiled gene expression in the same tissues.

RESULTS

We found a decrease in global DNA methylation and tissue folate and an increase in serum homocysteine with progression of gastric dysplasia. FA supplementation prevented this loss of global DNA methylation and markedly reduced gastric dysplasia and mucosal inflammation. FA protected against the loss of global DNA methylation both in the dysplastic gastric epithelial cells and in gastric stromal myofibroblasts. In addition, FA supplementation had an anti-inflammatory effect, as indicated by expression profiling and immunohistochemistry for lymphocyte markers.

CONCLUSIONS

We conclude that FA supplementation is chemopreventive in this model of Helicobacter-associated gastric cancer. The beneficial effect of FA is likely due to its ability to prevent global loss of methylation and suppress inflammation.

Genetic and epigenomic footprints of folate

Dietary micronutrient composition has long been recognized as a determining factor for human health. Historically, biochemical research has successfully unraveled how vitamins serve as essential cofactors for enzymatic reactions in the biochemical machinery of the cell. Folate, also known as vitamin B9, follows this paradigm as well. Folate deficiency is linked to adverse health conditions, and dietary supplementation with folate has proven highly beneficial in the prevention of neural tube defects. With its function in single-carbon metabolism, folate levels affect nucleotide synthesis, with implications for cell proliferation, DNA repair, and genomic stability. Furthermore, by providing the single-carbon moiety in the synthesis pathway for S-adenosylmethionine, the main methyl donor in the cell, folate also impacts methylation reactions. It is this capacity that extends the reach of folate functions into the realm of epigenetics and gene regulation. Methylation reactions play a major role for several modalities of the epigenome. The specific methylation status of histones, noncoding RNAs, transcription factors, or DNA represents a significant determinant for the transcriptional output of a cell. Proper folate status is therefore necessary for a broad range of biological functions that go beyond the biochemistry of folate. In this review, we examine evolutionary, genetic, and epigenomic footprints of folate and the implications for human health.

Autoimmune disease and subsequent risk of developing alimentary tract cancers among 4.5 million US male veterans

BACKGROUND

Autoimmunity is clearly linked with hematologic malignancies, but less is known about autoimmunity and alimentary tract cancer risk, despite the specific targeting of alimentary organs and tissues by several autoimmune diseases. The authors therefore conducted the first systematic evaluation of a broad range of specific autoimmune diseases and risk for subsequent alimentary tract cancer.

METHODS

On the basis of 4,501,578 US male veterans, the authors identified 96,277 men who developed alimentary tract cancer during up to 26.2 years of follow-up. By using Poisson regression methods, the authors calculated relative risks (RRs) and 95% confidence intervals.

RESULTS

A history of autoimmune disease with localized alimentary tract effects generally increased cancer risks in the organ(s) affected by the autoimmune disease, such as primary biliary cirrhosis and liver cancer (RR, 6.01; 95% confidence interval [CI], 4.76-7.57); pernicious anemia and stomach cancer (RR, 3.17; 95% CI, 2.47-4.07); and ulcerative colitis and small intestine, colon, and rectal cancers (RR, 2.53; 95% CI, 1.05-6.11; RR, 2.06; 95% CI, 1.70-2.48; and RR, 2.07; 95% CI, 1.62-2.64, respectively). In addition, a history of celiac disease, reactive arthritis (Reiter disease), and systemic sclerosis all were associated significantly with increased risk of esophageal cancer (RR, 1.86-2.86). Autoimmune diseases without localized alimentary tract effects generally were not associated with alimentary tract cancer risk, with the exception of decreased risk for multiple alimentary tract cancers associated with a history of multiple sclerosis.

CONCLUSIONS

These findings support the importance of localized inflammation in alimentary tract carcinogenesis. Future research is needed to confirm the findings and improve understanding of underlying mechanisms by which autoimmune diseases contribute to alimentary tract carcinogenesis.

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

Background

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

Methods

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

Results

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

Conclusions

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

Dietary folate and vitamin B6 are not associated with p53 mutations in esophageal adenocarcinoma

Recent studies have suggested an association between dietary folate, and related B-vitamins, and risk for cancer, potentially mediated by the p53 tumor suppressor gene. The aim of this study was to explore the effect of dietary folate and vitamin B(6) intake on p53 in the molecular pathogenesis of esophageal adenocarcinoma (EADC). For each participant, a structured questionnaire was used to obtain detailed sociodemographic and lifestyle risk factors, including diet, from which folate and vitamin B(6) intake were calculated. Risks for p53 mutations, p53 mutations at CpG sites, and p53 protein overexpression among EADC cases (n = 54) were calculated using logistic regression with dietary folate and vitamin B(6) intake as predictive variables, adjusting for age, gender, smoking, and alcohol consumption. No significant differences were found for patients with EADC who had p53 mutations (n = 21) compared with patients with wild-type p53 (n = 33) with respect to selected clinicopathologic variables (age, gender, tumor grade, stage, alcohol, or tobacco consumption) and dietary intake of folate or vitamin B(6). No statistically significant associations were seen between dietary folate and vitamin B(6) intake (highest vs. lowest quartiles) and p53 mutations, p53 mutations at CpG sites (n = 12), and p53 protein overexpression (n = 17). We conclude that dietary intake of folate and vitamin B(6) do not appear to have an effect on p53, suggesting alternative molecular mechanisms underlying esophageal adenocarcinogenesis.

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

BACKGROUND AND AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Vitamins B2 and B6 and genetic polymorphisms related to one-carbon metabolism as risk factors for gastric adenocarcinoma in the European prospective investigation into cancer and nutrition

B vitamins and polymorphisms in genes coding for enzymes involved in one-carbon metabolism may affect DNA synthesis and methylation and thereby be implicated in carcinogenesis. Previous data on vitamins B2 and B6 and genetic polymorphisms other than those involving MTHFR as risk factors for gastric cancer (GC) are sparse and inconsistent. In this case-control study nested within the European Prospective Investigation into Cancer and Nutrition cohort, cases (n = 235) and controls (n = 601) were matched for study center, age, sex, and time of blood sampling. B2 and B6 species were measured in plasma, and the sum of riboflavin and flavin mononucleotide was used as the main exposure variable for vitamin B2 status, whereas the sum of pyridoxal 5'-phosphate, pyridoxal, and 4-pyridoxic acid was used to define vitamin B6 status. In addition, we determined eight polymorphisms related to one-carbon metabolism. Relative risks for GC risk were calculated with conditional logistic regression, adjusted for Helicobacter pylori infection status and smoking status. Adjusted relative risks per quartile (95% confidence interval, P(trend)) were 0.85 (0.72-1.01, 0.06) for vitamin B2 and 0.78 (0.65-0.93, <0.01) for vitamin B6. Both relations were stronger in individuals with severe chronic atrophic gastritis. The polymorphisms were not associated with GC risk and did not modify the observed vitamin-cancer associations. In summary, results from this large European cohort study showed an inverse association between vitamin B2 and GC risk, which is borderline significant, and a significant inverse association between vitamin B6 and GC risk.

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

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

Serum folate and cancer mortality among U.S. adults: findings from the Third National Health and Nutritional Examination Survey linked mortality file

BACKGROUND

The relation between folate status and cancer is controversial. Several epidemiologic studies have suggested that increased folate intake is associated with reduced risk of various cancers, others have found no such associations, and a few have suggested that high folate intake might increase the risk of certain cancers.

METHODS

Using data from the Third National Health and Nutrition Examination Survey (NHANES III) Mortality File, a prospective cohort study of a nationally representative sample of 14,611 U.S. adults, we conducted Cox proportional hazards regression modeling to investigate the association of baseline serum folate concentrations and all-cancer mortality determined from linked death certificate data.

RESULTS

Relative to the lowest quintile of serum folate (<3.0 ng/mL), the multivariable-adjusted hazard ratios across quintiles 2 to 5 were: 1.61 [95% confidence interval (95% CI), 1.11-2.32], 1.00 (95% CI, 0.65-1.49), 1.39 (95% CI, 0.96-2.03), and 0.85 (95% CI, 0.59-1.22). These findings did not differ substantially by age or sex, but the higher risk for those in the second quintile appeared limited to non-Hispanic whites.

CONCLUSION

These findings suggest that there may be a nonlinear relationship between folate status and the risk of all-cancer mortality such that persons with low, but not grossly deficient, serum blood folate concentrations may be at increased risk. Further study is needed to determine whether these findings are due to chance, and if not, to clarify their biological basis.

Gastric cancer in relation to the intake of nutrients involved in one-carbon metabolism among MTHFR 677 TT carriers

BACKGROUND

DNA methylation is an important epigenetic process for transcriptional control of human genome including those genes involved in cancer initiation and progression. Clinical studies have suggested that biological explanation to the protective effect of some nutrients could be linked with the DNA methylation. Folate is a primary methyl donor nutrient; it has been shown to play a key role in DNA methylation, repair and synthesis, by acting as co-factors and/or substrates in this metabolic pathway. Likewise, activity of a key enzyme, the methylenetetrahydrofolate reductase (MTHFR) has also been shown to influence DNA methylation. Overall, these findings support the notion that dietary intake as well as genetic factors play a role in one-carbon metabolism.

AIM OF THE STUDY

This study is to evaluate the dietary intake of nutrients involved in one-carbon metabolism and the genotype of MTHFR 677 C > T with respect to GC risk.

METHODS

We carried out in January 2004 a population-based case-control study in the metropolitan area of Mexico City. A total of 248 histological confirmed GC patients were recruited from nine tertiary hospitals, along with 478 age and sex-matched controls. Nutrient intake was estimated from food frequency questionnaire; the MTHFR 677C > T genotype was determined by PCR-RFLP analysis.

RESULTS

A significant reduction in diffuse GC risk was observed for MTHFR 677 TT genotype among individuals with high consumption of folate (OR = 0.23; 95% CI 0.06-0.84), choline (OR = 0.55; 95% CI 0.33-0.9) and Vitamin B(6) (OR = 0.59; 95% CI 0.36-0.96) compared to MTHFR 677 CC + CT carriers. Among subjects with low consumption of methionine, a reduced risk of diffuse GC was also detected (OR = 0.40; 95% CI 0.16-0.97). In contrast, carriers of the MTHFR 677 TT genotype with a low consumption of folate had a significant increased risk of intestinal GC (OR = 1.88 95% CI 1.02-3.47). A folate-MTHFR 677 C > T interaction in the borderline of significance (P = 0.055) was detected.

CONCLUSIONS

It is probable that GC prevention requires dietary recommendations according to the individual genotype; nevertheless, the available information to this respect is still very limited.

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

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

MALDI-TOF MS genotyping of polymorphisms related to 1-carbon metabolism using common and mass-modified terminators

BACKGROUND

Large cohort studies may provide sufficient power to disentangle the role of polymorphisms related to 1-carbon metabolism and chronic diseases, but they require fast, accurate, high-throughput genotyping techniques. MALDI-TOF mass spectrometry has been adapted to rapid fine mapping using various approaches for allele discrimination. We developed a genotyping method based on MALDI-TOF MS and compared assay performance for formats based on standard and mass-modified terminators.

METHODS

The assay includes 20 polymorphisms of 14 genes involved in 1-carbon metabolism (BHMT 742G>A, CBS 844ins68 and 699C>T, CTH 1364G>T, DHFR del19, NOS3 -786T>C and 894G>T, FOLR1 1314G>A, MTHFD1 -105T>C and 1958G>A, MTHFR 677C>T and 1298A>C, MTR 2756A>G, MTRR 66A>G and 524C>T, SLC19A1 80G>A, SHMT1 1420C>T, TCN2 67A>G and 776C>G, and TYMS 1494del6).

RESULTS

Missing calls were observed for 4.7% of the DNA samples, attributed to failed liquid sample handling. Highly accurate genotyping was obtained by mass-modified as well as standard ddNTPs, with an average error rate of < or =0.1% by analysis of sample duplicates. A semiquantitative approach enabled unambiguous identification of the CBS 844ins68. Cluster plots of the relative allele intensities showed allele-specific bias according to type of minisequencing terminator and revealed a potential structural variation in the BHMT gene.

CONCLUSIONS

MALDI-TOF MS-based genotyping using either standard or mass-modified terminators allows the accurate determination of single nucleotides as well as structural genetic variants. This was demonstrated with 20 polymorphisms involved in 1-carbon metabolism.

Easy detection of 5,10-methylenetetrahydrofolate reductase 1298A/C genotype by mutagenically separated PCR assay

BACKGROUND

5,10-Methylenetetrahydrofolate reductase (MTHFR) plays a central role in folate metabolism. Previous studies have suggested an association between the MTHFR 1298A/C polymorphism and several diseases, such as cardiovascular and psychiatric diseases, neural tube defects, diabetes, and cancer. Currently, either PCR-restriction fragment length polymorphism (RFLP) technique or real-time PCR using Taqman assay are used to determine the MTHFR 1298 genotype.

METHODS

We developed a simple and efficient approach that employs mutagenically separated PCR to genotype MTHFR 1298A/C polymorphism. Two forward mutagenic allele-specific primers of different lengths for MTHFR 1298A/C were paired with the same reverse primer in a one-tube assay to genotype 20 genomic DNA samples.

RESULTS

Electrophoresis on 2.5% agarose gel showed two allele-specific fragments, a 113-bp A allele-specific and a 93-bp C allele-specific PCR product. The results were confirmed by the conventional PCR-RFLP method.

CONCLUSIONS

We conclude that mutagenically separated PCR could be used as an alternative simple, reliable, and cost-effective method for the genotyping of MTHFR 1298A/C polymorphism.

Dietary intake of selected micronutrients and gastric cancer risk: an Italian case-control study

BACKGROUND

A high consumption of non-starchy vegetables and fruits likely decreases the risk of gastric cancer, but no specific constituent of plant foods has been consistently identified to explain this association.

PATIENTS AND METHODS

We considered several micronutrients and minerals in an Italian case-control study conducted between 1997 and 2007, including 230 patients with incident, histologically confirmed gastric cancer and 547 matched controls, admitted with acute conditions. Micronutrients computation was based on a validated and reproducible food frequency questionnaire, through an Italian food composition database. We estimated odds ratios (ORs) using conditional logistic regression, adjusted for energy intake and selected covariates.

RESULTS

We found decreased ORs for the highest versus lowest quartile of vitamin E (OR=0.50), alpha-carotene (OR=0.52) and beta-carotene (OR=0.42) intake. Gastric cancer was directly associated with sodium, with ORs of 2.22 for the second, 2.56 for the third and 2.46 for the fourth quartile of intake. No significant relation emerged with iron, calcium, potassium, zinc, vitamin C, thiamin, riboflavin, niacin, vitamin B6, folate, vitamin D, retinol, beta-cryptoxanthin, lycopene and lutein plus zeaxanthin.

CONCLUSIONS

Our data support a favourable effect on gastric cancer of vitamin E and selected carotenoids and a detrimental effect of sodium even at intermediate levels of intake.