Abstract
Studies on the association of cytochrome p450 A1 (ml, m2), catechol-O-methyltransferase (COMT) H108L, glutathione S-transferase (GST) T1 and M1 polymorphisms with breast cancer risk were inconclusive. The current study was aimed to clarify the ambiguity in genetic associations of these enzymes with breast cancer risk on a global perspective. A systematic literature search was carried out in PubMed, Google Scholar and Medline, covering all the case-control studies published until September 2017. A meta-analysis was performed based on the random-effect and fixed-effect models to calculate the overall association of each genetic variant with breast cancer risk. Of the five polymorphisms studied, GSTT1 (OR: 1.07, 95% CI: 1.02-1.12 and OR: 1.08, 95% CI: 1.01-1.15 for fixed-effect and random-effect models, respectively) and GSTM1 (OR: 1.22, 95% CI: 1.17-1.26 and OR: 1.25, 95% CI: 1.12-1.35 for fixed-effect and random-effect models, respectively) null polymorphisms exhibited an increased risk for breast cancer in both the models. Cochrane Q-test and I-2 statistics revealed heterogeneity in association with these polymorphisms (P < 0.0001) with no evidence of publication bias. Thus, GSTT1 and GSTM1 null polymorphisms are risk factors for breast cancer.