Polymorphisms in GSTT1 and GSTM1 genes as possible risk factors for susceptibility to breast cancer development and their influence in chemotherapy response: a systematic review.

Breast cancer (BC) is a heterogeneous and multifactorial disease. The system formed by glutathione-S-transferases (GSTs) acts to protect the organism against the oxidative stress generated by xenobiotics and their active products. Glutathione transferase mu 1 (GSTM1) and glutathione transferase theta 1 (GSTT1) present null polymorphic variants by complete deletion. The absence of these enzymes may influence the susceptibility to several diseases such as BC. This study aimed to systematically review and investigate the existence of a possible correlation between the presence/absence of these genetic variants and the development of BC and their influence in chemotherapy response. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol was used, and the searches were performed in the portal of the Virtual Health Library (VHL) and the PubMed, resulting in 21 articles. It is clear that most studies revealed a risk association between the deletion of GSTM1 and/or GSTT1 and the development and/or prognosis of BC.Moreover, it should be noted that these results of risk association were found in large part in the populations of the Americas and Europe, followed by Asians. Regarding the response to treatment, protective associations were found in the presence of GSTM1 deletion. However, due to the inconclusive results of many studies, further analysis in this area is required.