Genetic polymorphismsin genes related to the metabolism of xenobiotics, such as genes of the glutathioneS-transferases (GSTM1, GSTT1, and GSTP1) superfamily havebeen associated with an increased risk for breast cancer (BC). Considering thehigh incidence of BC in the city of Porto Alegre in southern Brazil, the purposeof this study was to characterize genotypic and allelic frequencies of polymorphismsin GSTM1, GSTT1, and GSTP1, and correlate these molecular findingswith established risk factors for breast cancer including mammographic density,in a sample of 750 asymptomatic women undergoing mammographic screening. Moleculartests were performed using the multiplex polymerase chain reaction (PCR) forGSTM1 and GSTT1, and quantitative PCR for GSTP1 polymorphisms.Overall, the frequencies of GSTM1 and GSTT1 null genotypes were45% and 21%, respectively. For GSTP1 polymorphism, genotypic frequencieswere 44% for the Ile/Ile genotype, 44% for the Ile/Val genotype, and 12% forVal/Val genotype, with an allelic frequency of 66% for the wild type allelein this population, similar to results of previous international publications.There was a statistically significant association between the combined GSTM1and GSTT1 null genotypes (M-/T-) and mammographic density in post menopausalwomen (p = 0.031). When the GSTT1 null (T-) genotype was analyzed isolated,the association with mammographic density in post menopausal women and in theoverall sample was also statistically significant (p = 0.023 and p = 0.027,respectively). These findings suggest an association of GSTM1 and GSTT1null genotypes with mammographic density.
