DNA methylation is one of the major events in the early process of gastric carcinogenesis and also occurs in non-neoplastic gastric mucosa. Catechol-O-methyltransferase (COMT) catalyzes the methylation of various endobiotic and xenobiotic substances, and protects DNA from oxidative damage. The association between a common functional polymorphism of COMT Val158Met and DNA methylation status in the stomach was investigated.
Patients and methods: One hundred and sixty-nine gastric mucosa samples from non-cancer patients were obtained by endoscopy. The promoter methylation status of p14 and p16 was determined by methylation-specific PCR (MSP). The COMT Val158Met polymorphism was detected by PCR-restriction fragment length polymorphism (RFLP).
Results: CpG island methylation was observed in 32.5% of the p14, and 37.9% of the p16. The methylation status of both p14 and p16 was not associated with gender or age, while p16 methylation was strongly associated with Helicobacter pylori infection (OR=4.71, 95% CI=2.35-9.46, p<0.0001). The Val/Val genotype held a significantly higher risk of p16 methylation (OR=3.27, 95% CI=1.05-10.25, p=0.0418).
Conclusion: The COMT polymorphism may influence the susceptibility to gene methylation in the gastric mucosa. The promoter CpG island of p16 gene, but not of p14 may be one of the specific regions whose methylation is closely influenced by the COMT polymorphism.