Mifepristone: Antineoplastic studies

Emerging research suggests that mifepristone may have significant clinical applications in the treatment of certain neoplastic disorders. For example, in vitro studies have shown that RU-486 can inhibit or stimulate--depending on the cell line and the hormonal milieu of the culture medium--the growth of breast cancer cells. In hormone-sensitive breast cancer, anti-tumor activity is maximized by treatment with a combination of RU-486 and estrogen antagonists such as tamoxifen or luteinizing hormone releasing hormone analogues. The few studies of RU-486 administration in women with advanced breast cancer that had failed to respond to tamoxifen have demonstrated short-term disease stabilization (e.g., 5-10 months). This research has suggested that progesterone receptors are necessary but not sufficient for anti-tumor responses. Also promising, although untested in a large-scale study, is use of RU-486 in women with progressive recurrent and/or unresectable benign meningiomas. In addition, RU-486 has inhibited hormone-insensitive human prostate cancer cell lines grown in vitro and in nude mice xenografts.