For instance, as monotherapy, mifepristone was demonstrated to block the proliferation of breast cancer cells carrying PR and ER, such as T-47D and MCF-7 cells in the absence or presence of estrogens (Bardon et al. 1985, Horwitz 1985, Gill et al. 1987, Musgrove et al. 1997). This evidence concerns the gene ESR1 and breast carcinoma.