Detailed biochemical studies of steroid hormone receptor cross-talk are needed to provide a framework for a better understanding of differential hormone actions in pre- and post-menopausal conditions where endogenous hormone levels dramatically differ, as well as during breast or prostate cancer treatment with hormone-ablation therapies where closely related steroid hormone receptors (PR, GR, AR, ER) may substitute for the blocked activity of another (ER or AR). This evidence concerns the gene ESR1 and prostate cancer.