Global DNA methylation and tumor suppressor gene promoter methylation and gastric cancer risk in an Omani Arab population

Aim: We carried out a case-control study in an Omani Arab population to investigate the association between gastric cancer and peripheral blood leukocyte DNA methylation in LINE-1 and in the tumor suppressor genes CDH1, p16, TP53 and RUNX3. Materials & methods: We quantified methylation (% 5-mC) in DNA extracted from peripheral blood leukocytes via pyrosequencing. We calculated odds ratios (ORs) and 95% Cls using logistic regression. Results: We found patterns of global hypomethylation (LINE-1: ORcontinuous = 0.59; 95% Cl: 0.42-0.82) and TP53 promoter hypomethylation (ORcontinuous = 0.64; 95% Cl: 0.16-0.85) for cases versus controls; p16 promoter region hypomethylation was not statistically significant. Evaluating LINE-1, TP53 and p16 jointly yielded a more pronounced negative association with gastric cancer (OR: 0.24; 95% Cl: 0.09-0.66). Age was a significant effect modifier. We found no differences by tumor grade, stage or histology. Conclusion: We found a pattern of global hypomethylation and promoter region hypomethylation of TP53 and p16 in cases versus controls for this population of Omani Arabs.