Objective: To study the relationship between polymorphism of inducible Nitric Oxide Synthase (iNOS) gene and the susceptibility of intestinal type stomach cancer and stomach cardia cancer in Chinese people.
Methods: A community-based case-control study was designed. Ninety-three intestinal type of stomach cancer and 50 stomach cardia cancer patients with endoscopy and pathology diagnosis were identified as cases. Two hundred and forty-six controls served as controls.
Results: C-->T polymorphism was found in exon 16 of iNOS gene, which changed the coding amino acid from serine to leucine, and formed a recognition site identified by Tsp 509 I restriction enzyme (we called it C-->T polymorphism). The T allele gene frequency in the control group was 13.21%. No statistically significant difference was found between C-->T polymorphism alone and the increased susceptibility to intestinal stomach cancer or stomach cardia cancer. A significant type 2 multiplicative interaction was found in increasing both the risk of intestinal stomach cancer and stomach cardia cancer when both C-->T polymorphism and tobacco smoking exposure existed. An additive interaction model, which showed statistically significant difference, was found to increase only the risk of stomach cardia cancer when CagA antibody shared negative but C-->T polymorphism occurred.
Conclusion: C-->T polymorphism of iNOS gene was considered as one of the possible susceptible genes, which specifically increased the risk of tobacco-related but CagA negative types of intestinal stomach cancer and stomach cardia cancer.