A Meta-Analysis About The Association Between Glutathione S-Transferase Gene Polymorphisms And Breast Cancer Risk

Background and objective GST (Glutathione s-transferase) enzymes are the most important phase Ⅱ metabolic enzymes, and GST genes polymorphisms can lead to deficiency or decrease of relevant enzymatic activity. Many studies have been conducted to reveal the association between GST genes polymorphisms and breast cancer risk, but there remained no definite conclusion. In order to estimate the association in depth, we performed the meta-analysis of 92 original published studies, as well as accumulated meta-analysis.Methods Eligible studies were searched from databases. Pooled odds ratios (OR) with the corresponding 95% confidence (95%CI) were adopted to evaluate the relevancy strength between the GST gene polymorphisms and breast cancer risk. Q Test and I2 were used to assess the heterogeneity. Begg’s funnel plot and Egger’s test were used to assess publication bias. STATA 11.0 statistical analysis software was conducted to make the meta-analysis.Results Significant association were found between GSTT1 (null vs. present, OR=1.19,95%CI:1.09-1.30; I2=63.4%), GSTM1 gene polymorphism (null vs. present, OR=1.16,95%CI:1.09-1.23; I2=61.9%) and breast cancer risk, no association was between in GSTP1 gene polymorphism and breast cancer risk in the overall population. The cumulative meta-analyses got consistent results with the pooled results. In the subgroup analysis, Asian and Caucasian got consistent positive results, but the African-American indicated no significant association with GSTT1 or GSTM1. Neither menopausal status nor source of control changed the significant association; About GSTP1 polymorphism, significant association were only found in Asian population (GG+AG/AA: OR=1.27,95%CI:1.02-1.57; I2=89.7%). In the subgroup analysis by HWE (Hardy-Weinberg equilibrium), significant association was only found in the group which conformed to HWE (allele model, G/A:OR=1.09,95%CI: 1.01-1.18; 12=73.1%).Conclusion GSTM1 and GSTT1 polymorphisms are associated with breast cancer risk, and racial difference existed in them; GSTPl polymorphism is associated with breast cancer risk in Asian population, but sophisticated and larger sample studies are needed to confirm.