The role of non-genomic actions of progesterone and its membrane receptor agonist in ovarian cancer cell death.

Abstract

Progesterone therapy is a relatively inexpensive treatment option for endometrial and breast cancers, with few side effects. Two signaling pathways usually mediate the physiological effects of progesterone, namely genomic and non-genomic actions. Genomic action occurs slowly via the nuclear progesterone receptor (PR), whereas the membrane progesterone receptor (mPR) induces rapid non-genomic action. We investigated the effects of progesterone and various PR agonists on ovarian cancer cells. PR expression of six serous ovarian cancer cell lines was examined by western blotting, and mPR expression was examined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). PR-negative and mPR-positive ovarian cancer cells were exposed to progesterone and seven types of PR agonists (medroxyprogesterone acetate [MPA], dehydroepiandrosterone, dienogest, levonorgestrel, drospirenone, pregnenolone, and allopregnanolone) at 10-400 μM, and viable cell counts after exposure for 30 min were measured using the water-soluble tetrazolium (WST-1) assay. Ovarian cancer cell lines were exposed to 100 μM progesterone, and the expression of BAX, a pro-apoptotic protein, after 1-5 min was examined by western blotting. Western blotting detected no PR expression in the six serous ovarian cancer cell lines. In contrast, RT-qPCR detected mPR expression in all six serous ovarian cancer cell lines. Progesterone and MPA-induced cell death in all tested ovarian cancer cell lines in a concentration-dependent manner, whereas no effect was observed for other PR agonists. Western blotting revealed that pro-apoptotic protein BAX expression occurred 1 min after exposure to progesterone, suggesting that the cytocidal effects are mediated by rapid non-genomic action. Progesterone and MPA exhibited a rapid cytocidal effect on PR-negative ovarian cancer cells through non-genomic action. Progesterone and MPA could be novel adjuvant therapies for ovarian cancer.