ESR2 and prostate cancer: In a xenograft model of prostate cancer cells that expresses the endogenous BPA-responsive AR-T877A mutant protein, BPA enhances tumor cell proliferation after androgen deprivation and increases the prostate-specific antigen level, indicating that the AR, at least partially, mediates the effects of BPA.114 In another study, BPA induced a distinct gene expression signature in prostate cancer cells expressing an AR mutation.115 Particularly, a major action of BPA was to down-regulate ER-β.