CYP19A1 and neoplasm: Various drugs such as medroxyprogesterone acetate, megestrol acetate, tamoxifen, aromatase inhibitors, and GnRH agonists have been tried, but with varied rates of response.[8] Progestins act as chemopreventive agents by inducing apoptosis pathways involving transforming growth factor α (TGF-α) in the ovarian epithelium, a plausible local mechanism for inhibiting tumor growth.