Collectively, the discovery of E2-induced apoptosis not only has clinical relevance to treat aromatase inhibitor-resistant breast cancer and reduce breast cancer incidence in postmenopausal women[29,110], but also a general principal has emerged to understand sex steroid-induced apoptosis in long-term androgen deprived prostate cancer[128]. This evidence concerns the gene CYP19A1 and prostate carcinoma.