GSTM1 and GSTT1 gene deletions and the risk for nasopharyngeal carcinoma in Han Chinese.

Southern China is a major nasopharyngeal carcinoma-endemic region. Environmental factors and genetic susceptibility contribute to nasopharyngeal carcinoma development in this area. Polymorphic deletions of GSTM1 and GSTT1 genes involved in the detoxification of potentially carcinogenic agents may be a risk factor for nasopharyngeal carcinoma. To investigate the roles of genetic variations of GSTM1 and GSTT1 in nasopharyngeal carcinoma susceptibility in the Chinese population, we conducted a case-control study of 350 nasopharyngeal carcinoma cases and 622 controls. GSTM1 and GSTT1 deletion variants were genotyped by multiplex PCR assays. Logistic regression analysis was used to estimate odds ratios and 95% confidence intervals (95% CI). No significant association was observed for either GSTM1- or GSTT1-null genotype independently in the contribution to nasopharyngeal carcinoma risk. To explore possible joint effects of the GSTM1- and GSTT1-null polymorphisms with each other and with other risk factors for nasopharyngeal carcinoma, we examined the association between each combined genotype and the risk for nasopharyngeal carcinoma stratified by gender and EBV replication status. We found that individuals who carried GSTM1/GSTT1-double null genotype had a higher risk for nasopharyngeal carcinoma in the male population (odds ratio, 1.76; 95% confidence interval, 1.04-2.97; P = 0.03); however, this was not significant after correction for multiple comparisons. No statistical difference was found between cases and controls in females and the subpopulation positive for immunoglobulin A antibodies to EBV capsid antigen for combined genotypes. Our results suggest that the GSTM1/GSTT1-double null genotype may be a risk factor for nasopharyngeal carcinoma among males in southern China, but this result warrants confirmation in other studies.