In addition, it has been shown that MCF-7 made resistant to 4-hydroxytamoxifen also respond to mifepristone monotherapy undergoing apoptotic death [46]; finally, although at higher concentrations, mifepristone was also cytotoxic to progesterone receptor- and estrogen receptor-negative MDA-MB-231 breast cancer cells [47]. The gene discussed is PGR; the disease is breast carcinoma.