Diet Folate, DNA Methylation and Polymorphisms in Methylenetetrahydrofolate Reductase in Association with the Susceptibility to Gastric Cancer

Methylenetetrahydrofolate reductase (MTHFR) has been reported to be associated with DNA methylation, anepigenetic feature frequently found in gastric cancer. We conducted a case-control study to explore the associationof MTHFR C677T polymorphisms with gastric cancer risk and its relation with the DNA methylation of COX-2,MGMT, and hMLH1 genes. Genotyping of P16, MGMT and HMLH1 was determined by methylation-specificPCR after sodium bisulfate modification of DNA, and genotyping of MTHFR C677T was conducted by TaqManassays using the ABI Prism 7911HT Sequence Detection System. Folate intake was calculated with the aid ofa questionnaire. Compared with the MTHFR 677CC genotype, the TT genotype was significantly associatedwith 2.08 fold risk of gastric cancer when adjusting for potential risk factors. Individuals who had an intakeof folate above 310 μg/day showed protective effects against gastric cancer risk. The effect of MTHFR C677Tpolymorphisms on the risk of gastric cancer was modified by folate intake and methylation status of MGMT (Pfor interaction <0.05).