Antiprogestin mifepristone inhibits the growth of cancer cells of reproductive and non-reproductive origin regardless of progesterone receptor expression

<p>Abstract</p> <p>Background</p> <p>Mifepristone (MF) has been largely used in reproductive medicine due to its capacity to modulate the progesterone receptor (PR). The study of MF has been expanded to the field of oncology; yet it remains unclear whether the expression of PR is required for MF to act as an anti-cancer agent. Our laboratory has shown that MF is a potent inhibitor of ovarian cancer cell growth. In this study we questioned whether the growth inhibitory properties of MF observed in ovarian cancer cells would translate to other cancers of reproductive and non-reproductive origin and, importantly, whether its efficacy is related to the expression of cognate PR.</p> <p>Methods</p> <p>Dose-response experiments were conducted with cancer cell lines of the nervous system, breast, prostate, ovary, and bone. Cultures were exposed to vehicle or increasing concentrations of MF for 72 h and analysed for cell number and cell cycle traverse, and hypodiploid DNA content characteristic of apoptotic cell death. For all cell lines, expression of steroid hormone receptors upon treatment with vehicle or cytostatic doses of MF for 24 h was studied by Western blot, whereas the activity of the G1/S regulatory protein Cdk2 in both treatment groups was monitored <it>in vitro </it>by the capacity of Cdk2 to phosphorylate histone H1.</p> <p>Results</p> <p>MF growth inhibited all cancer cell lines regardless of tissue of origin and hormone responsiveness, and reduced the activity of Cdk2. Cancer cells in which MF induced G1 growth arrest were less susceptible to lethality in the presence of high concentrations of MF, when compared to cancer cells that did not accumulate in G1. While all cancer cell lines were growth inhibited by MF, only the breast cancer MCF-7 cells expressed cognate PR.</p> <p>Conclusions</p> <p>Antiprogestin MF inhibits the growth of different cancer cell lines with a cytostatic effect at lower concentrations in association with a decline in the activity of the cell cycle regulatory protein Cdk2, and apoptotic lethality at higher doses in association with increased hypodiploid DNA content. Contrary to common opinion, growth inhibition of cancer cells by antiprogestin MF is not dependent upon expression of classical, nuclear PR.</p

Advanced assessment of migration and invasion of cancer cells in response to mifepristone therapy using double fluorescence cytochemical labeling

Abstract Background Previous work in our laboratory demonstrated that antiprogestin mifepristone impairs the growth and adhesion of highly metastatic cancer cells, and causes changes in their cellular morphology. In this study, we further assess the anti-metastatic properties of mifepristone, by studying whether cytostatic doses of the drug can inhibit the migration and invasion of various cancer cell lines using a double fluorescence cytochemical labeling approach. Methods Cell lines representing cancers of the ovary (SKOV-3), breast (MDA-MB-231), glia (U87MG), or prostate (LNCaP) were treated with cytostatic concentrations of mifepristone. Wound healing and Boyden chamber assays were utilized to study cellular migration. To study cellular invasion, the Boyden chamber assay was prepared by adding a layer of extracellular matrix over the polycarbonate membrane. We enhanced the assays with the addition of double fluorescence cytochemical staining for fibrillar actin (F-actin) and DNA to observe the patterns of cytoskeletal distribution and nuclear positioning while cells migrate and invade. Results When exposed to cytostatic concentrations of mifepristone, all cancer cells lines demonstrated a decrease in both migration and invasion capacities measured using standard approaches. Double fluorescence cytochemical labeling validated that mifepristone-treated cancer cells exhibit reduced migration and invasion, and allowed to unveil a distinct migration pattern among the different cell lines, different arrays of nuclear localization during migration, and apparent redistribution of F-actin to the nucleus. Conclusion This study reports that antiprogestin mifepristone inhibits migration and invasion of highly metastatic cancer cell lines, and that double fluorescence cytochemical labeling increases the value of well-known approaches to study cell movement