PGR and cancer: Indeed we have shown that cancer cells of different tissues of origin and different degrees of hormone-dependency, such as MCF-7 breast cancer cells carrying PR, MDA-MB-231 breast cancer cells with no PR expression, PR negative and androgen receptor positive LNCaP prostate cancer cells, and PR negative androgen receptor positive PC3 prostate cancer cells are all inhibited by mifepristone with similar potency [40], strongly suggesting that the presence of the PR is not required for the inhibition of cancer growth triggered by antiprogestins.