GSTT1 and GSTM1 null genotypes and the risk of gastric cancer: a case-control study in a Chinese population.

Glutathione S-transferase (GST) enzymes are involved in detoxification of many potentially carcinogenic compounds. The homozygous deletions or null genotypes of GSTT1 (theta class) and GSTM1 (mu class) genes may be associated with an increased risk of cancer. Few studies have evaluated the relationship between GSTT1, GSTM1 and the risk of gastric cancer, as well as the potential interactions between these genetic markers and other risk factors of gastric cancer in the Chinese population. We conducted a case-control study with 143 cases with gastric cancer, 166 chronic gastritis (CG) cases and 433 cancer-free population controls from Yangzhong County, China. The epidemiological data were collected by a standard questionnaire for all of the subjects, and blood samples were obtained from 91 gastric cancer cases, 146 CG cases, and 429 controls. GSTT1 and GSTM1 genotypes were assayed by the PCR method, and Helicobacter pylori infection was measured by the ELISA method. Using logistic regression model in SAS, we assessed the independent effects of GSTT1 and GSTM1 null genotypes on the risk of gastric cancer and their potential interactions with other factors. The prevalence of GSTM1 null genotype was 48% in gastric cancer cases, 60% in CG patients, and 51% in controls. The prevalence of GSTT1 null genotype was 54% in gastric cancer cases, 48% in CG patients, and 46% in controls. After controlling for age, gender, education, pack-years of smoking, alcohol drinking, body mass index, H. pylori infection, and fruit and salt intake, the adjusted odds ratio (OR) for GSTT1 and gastric cancer was 2.50 (95% confidence interval (CI), 1.01-6.22). When gastric cancer cases were compared with CG patients, the adjusted OR for GSTT1 was 2.33 (95% CI, 0.75-7.25). However, GSTT1 null genotype was not associated with the risk of CG when using population controls. No obvious association was found between GSTM1 and the risk of both gastric cancer and CG. Our results suggest that GSTT1 null genotype may be associated with an increased risk of gastric cancer in a Chinese population.