Association between androgen receptor gene CAG repeat polymorphism and breast cancer risk: a meta-analysis

Androgens have been hypothesized to influence risk of breast cancer through several possible mechanisms, including their conversion to estradiol and their binding to the estrogen receptor and/or androgen receptor (AR) in the breast. The CAG repeat polymorphism in AR exon 1 has been implicated in breast cancer risk; however, studies on the association between this polymorphism and breast cancer risk remain conflicting. In order to derive a more precise estimation of the relationship, a large population-based case–control study was performed. We found that a long CAG sequence has a protective effect on breast cancer using an a priori determined cutoff (<22 or ≥22) in a dominant model analysis [SL–LL vs. SS, odds ratio (OR) = 0.86, 95% confidence intervals (CI): 0.67–1.10]. A similar result was obtained by analyzing seven detailed genotyping case–control studies by allele comparison in dominant and recessive models. However, larger scale primary study is required to further evaluate the interaction of AR CAG polymorphism and breast cancer risk.