Hence, we could conclude that the results of the studies concerning both GSTM1 and GSTT1 are stable and credible. Bias diagnostics Funnel plots were usually created to assess the possible publication biases. In the meta-analyses, for GSTT1 and GSTM1 polymorphisms, the

funnel plots were not created because it is useless when the number of the included studies is limited. Nevertheless, fail-safe number, for the evaluation of the reliability of meta-analysis, is defined as the number of negative results that could reverse the significant finding. The Nfs0.05 for GSTM1 polymorphism was 66, suggesting that the publication biases might not have a remarkable influence on the results of the meta-analyses. Notably, for GSTT1 polymorphism, it is useless to utilize fail-safe number SC75741 chemical structure for evaluation of publication bias when the number of the included studies is only four. Discussion Previous evidence suggests that GSTM1 and GSTT1 polymorphisms may have a close association with increased susceptibility to various carcinomas. this website In the present study, the results of meta-analyses suggest that genetic deletion of GSTM1 may contribute to increased susceptibility to NPC whereas GSTT1 polymorphism may not. Null mutations of GSTM1, one of the most important phase II enzymes, are known to abolish enzyme activities and therefore have been linked with increasing incidence of certain

cancers, most likely due to increased susceptibilities to environmental toxins and carcinogens. Previous meta-analyses indicate that GSTM1 deficiency might have a significant association with increased risks of breast XAV-939 cost cancer [17] and lung cancer in Chinese people [18]. Our previous meta-analyses concerning oral cancer suggest that GSTM1 null

genotype increases the oral cancer risk in Asians but not Caucasians [19]. However, a number of meta-analyses suggest no marked associations of GSTM1 null mutations with hepatocellular carcinoma [20], brain tumors [21], gastric cancer [22], esophageal cancer [23] and prostate cancer [24]. In this study, the results supported the notion that GSTM1 deficiency might increase susceptibility to NPC. Similarly, null genotype of GSTT1 has been suggested Evodiamine to associate with risks of a number of cancers. Previous meta-analyses suggest marked associations of GSTT1 deletion with lung cancer [25], gastric cancer in Caucasians [26], brain cancers [21], colorectal cancer [27], leukaemia [28] and head and neck cancers that combined oral and pharyngeal as well as laryngeal cancers [29]. In the present meta-analysis, GSTT1 deficiency is unlikely to act as a risk factor for NPC, in line with previous meta-analyses concerning esophageal cancer [23], prostate cancer [24] and breast cancer [30], respectively. Notably, for GSTT1, the results should be interpreted with caution because of the limited number of the included studies.