A.K. Lopes et al. 2 literature was conducted in the PubMed database using combinations of the following descriptors and Boolean operators 'GSTM1 and GSTT1', [AND] 'oral cancer', [AND] 'polymorphism'. A metaanalysis of GSTT1 and GSTM1 null polymorphisms in patients with oral cancer (cases) and cancer-free individuals (controls) from each of the studies was performed. The data of each study were analyzed, and the odds ratio, the 95% confidence interval, and the number of patients were determined for each study and for all studies combined. The number of individuals analyzed was 7,839, 44.3% presenting with oral cancer and 55.7% healthy controls. The meta-analysis showed that GSTT1 and GSTM1 were associated with protection against oral cancer. A significant association of GSTT1 and GSTM1 null polymorphisms with an increased risk of developing oral cancer was observed. These findings point to a synergistic relationship between environmental and genetic factors in the development of oral cancer tumors.

Human papillomavirus (HPV) infection is the main risk factor for cervical cancer. Other risk factors include smoking and genetic susceptibility. Glutathione-S-transferases (GST) are enzymes involved in tobacco carcinogen metabolism, and genes encoding these enzymes are highly polymorphic. We compared the frequencies of GSTM1 and GSTT1 null polymorphisms in women with cervical cancer and in a control group, as well as to determine possible associations between such polymorphisms, cigarette smoking and the prognosis of cervical cancer. The series comprised 135 cervical cancer patients and 100 women without cancer. Genotypes were ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 18 (1): gmr18067 A.L.M. Tacca et al. 2 investigated by PCR. The results were compared using the Chisquare test or Fisher's exact test, and survival analysis by Kaplan-Meier test and Log-rank. Among the cases, the frequency of GSTM1 gene null polymorphism was 22.2%, and for the GSTT1 gene it was 48.5%. Among the controls, the frequency of the GSTM1 gene null polymorphism was 45.0%, while for GSTT1 it was 56.0%. A significant association was found between smoking and cervical cancer (P= 0.0062; OR = 2.16). Differently from GSTM1, the GSTT1 null polymorphism was not associated with cervical cancer risk in this study. The GSTT1 null genotype was significantly associated with worse prognosis. The overall survival rate for the cervical cancer group was 78.5%, and when stratified by genotypes, survival was higher in patients presenting at least one of the alleles, GSTT1 or GSTM1, indicating a higher risk of death for those presenting dual nullity (P= 0.031; RR = 2.458).