Association Between GSTM1 Polymorphism and Nasopharyngeal Cancer Susceptibility: a Meta-analysis

Abstract

Background/Aims: Glutathione S-transferase M1 (GSTM1) is a multifunctional enzyme that plays a criticalrole in the detoxification of varieties of carcinogenic metabolites. Many studies have been conducted to investigatethe association between GSTM1 polymorphism and nasopharyngeal cancer (NPC) risk, but the findings amongthose studies are inconsistent. To assess this relationship more precisely, we performed a meta-analysis of allavailable studies on the subject. <br/><b>Methods</b>: Case-control studies were identified by searching Pubmed, Embase,ISI Web of Science, and Wanfang databases through September 6, 2012. We used the pooled odds ratio (OR)with its corresponding 95% confidence interval (95%CI) to evaluate the association of GSTM1 polymorphismwith NPC susceptibility. Subgroup analyses by pathological types, sex and smoking status were performed tofurther identify the association. <br/><b>Results</b>: Overall, 11 published studies with 1,513 cases and 2,802 controls werefinally included into this meta-analysis according to the inclusion criteria. Meta-analysis of total studies showedthat the null genotype of GSTM1 was significantly associated with increased risk of NPC, when comparing withthe non-null genotype (OR=1.51, 95%CI=1.33-1.72, POR<0.001). The association was still statistically significantin subgroup analysis of patients with nasopharyngeal squamous cell carcinoma (OR=1.73, 95%CI=1.24-2.42,POR=0.001). Males with the null genotype of GSTM1 were more likely to subject to NPC than females. Inaddition, the association between the null genotype of GSTM1 and NPC risk was strongest in individuals withexposure to smoking. Sensitivity analysis by sequential omission of any individual studies one at a time furtherdemonstrated the significant association. <br/><b>Conclusions</b>: The findings suggest that the null genotype of GSTM1 isa risk factor for NPC, and there is a gene- smoking interaction in this association