ESTUDO DE POLIMORFISMOS NULOS NOS GENES GSTT1 E GSTM1 E SUAS ASSOCIAÇÕES AO TABAGISMO E AO CÂNCER DE COLO UTERINO.

Abstract

The main risk factor for cervical cancer is infection with the Human Papillomavirus (HPV). However, other risk factors are required for the development of cervical cancer, among them, smoking and genetic susceptibility have been proven relevant. Enzymes named Glutathione-S-Transferase (GST) are responsible for the metabolism of tobacco carcinogens and the genes encoding these enzymes are highly polymorphic. The objective of this study was to compare the frequencies of GSTM1 and GSTT1 null polymorphisms in women with cervical cancer and in women with no history of cancer, as well as the possible associations between such genetic polymorphisms, cigarette smoking and the prognosis of cervical cancer. The series consisted of 135 patients with cervical cancer and 100 participants without cancer. Genotypes were investigated by means of polymerase chain reaction (PCR). The results were compared using the Chi-square test or Fisher's exact test, and survival analysis by Kaplan-Meier tests and Log-rank. Among the cases, the frequency for 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 the GSTT1 gene null polymorphism it was 56.0%. Important association was demonstrated between smoking and cervical cancer (p= 0.0062; OR = 2.16). The results showed that the GSTM1 and GSTT1 null genotypes were not associated with cervical cancer in the population studied. In addition, GSTM1 genotype was significantly associated to a better prognosis of the tumors, decreasing the risk of metastasis (p= 0.014; OR = 3.45). The overall survival rate for the group was 78.5% and, when stratified by genotypes studied, survival was higher in patients with positive genotypes, indicating a higher risk of death in the presence of dual nullity (p= 0.031; RR = 2.458).