The role of GSTA2 polymorphisms and haplotypes in breast cancer susceptibility: A case-control study in the Portuguese population

Glutathione-S-transferases (GSTs) are a super-family of phase II metabolizing enzymes that catalyse the detoxification of a large range of endogenous and exogenous toxic compounds, playing an important role in protecting cells against damage, through glutathione conjugation with electrophilic substances. Polymorphic variation in these enzymes that affect its activity seems to be related to individual susceptibility to various human diseases, including cancer. Of the GST super-family, the alpha class GSTs have commonly been described as one of the most versatile class, since it is responsible for detoxification of compounds such as bilirubin, bile acids and penicillin, thyroid and steroid hormones, allowing its solubilization and storage in the liver. Among the alpha class, GSTA1 and GSTA2 isoforms are the most widely expressed in human tissues. Additionally, these enzymes can catalyse conjugation of the nitrogen mustard group of alkylating anticancer drugs, some heterocyclic amines and α,β-unsaturated aldehydes. Since some risk factors for increased breast cancer risk could be related to high production of reactive oxygen species during the metabolism of estrogens by catechol estrogens, or to the exposure to genotoxic compounds, and some of these toxic compounds are usually metabolized by GSTA2, we carried out a hospital based case-control study in a Caucasian Portuguese population (291 breast cancer patients without familiar history of breast cancer and 547 controls matched for age, sex and ethnicity) in order to evaluate the potential modifying role of three non-synonymous polymorphisms in the GSTA2 gene (P110S Ex 5+56C>T;, rs2234951; S112T Ex5+63G>C, rs2180314 and E210A Ex7+83A>C, rs6577) on the individual susceptibility to breast cancer. Our data show that the studied polymorphisms are in strong linkage disequilibrium, but no association was observed between individual GSTA2 polymorphisms and haplotypes and individual susceptibility to breast cancer.