Background and aims: Stimulation of inducible nitric oxide synthase gene expression by Helicobacter pylori, with subsequent overproduction of nitric oxide, has been implicated in gastric carcinogenesis. We investigated whether inducible nitric oxide synthase promoter gene polymorphisms are associated with (a) inducible nitric oxide synthase mRNA expression in the gastric mucosa, and (b) the risk of gastric carcinoma.
Materials and methods: The relationship between gastric inducible nitric oxide synthase mRNA expression and inducible nitric oxide synthase promoter polymorphisms (CCTTT repeat polymorphism and -2445 C-->G SNP) was examined in 74 H. pylori-infected patients with gastric cancer, peptic ulcer, or functional dyspepsia. In a case-control study the prevalence of the polymorphisms was examined in H. pylori-infected gastric carcinomas (n=77) and noncancerous controls (n=154).
Results: Inducible nitric oxide synthase mRNA levels were significantly higher in long CCTTT repeat (either allele>11) carriers than in short ones (P=0.015). Multivariate regression analysis showed that inducible nitric oxide synthase mRNA expression was significantly linked to long CCTTT repeat and gastric cancer (P=0.026), but not to -2445 C-->G SNP and other parameters. The case-control study showed that long CCTTT repeat carriers had an increased risk of gastric cancer with an odds ratio of 2.0 (P=0.021). -2445 C-->G SNP was not associated with the risk.
Conclusions: Helicobacter pylori induces higher inducible nitric oxide synthase mRNA expression in carriers of long CCTTT repeats of inducible nitric oxide synthase promoter, and this polymorphism is associated with an increased risk of gastric carcinoma.