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Progesterone Receptor (PR) Isoforms PRA and PRB Differentially Regulate Expression of the Breast Cancer Resistance Protein in Human Placental Choriocarcinoma BeWo Cells

Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, Washington (H.W., E.-W.L., L.Z., J.D.U., Q.M.), and Department of Life Science and Biotechnology, College of Natural Science, Dongeui University, Busan, Korea (E.-W.L.); Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, British Columbia, Canada (P.C.K.L.); and University of Maryland Greenebaum Cancer Center and School of Medicine, and the Baltimore VA Medical Center, Baltimore, Maryland (D.D.R.)

Breast cancer resistance protein (BCRP) plays a significant role in drug disposition and in conferring multidrug resistance in cancer cells. Previous studies have shown that steroid hormones such as 17β-estradiol and progesterone can affect BCRP expression in cancer cells. In this study, we investigated the molecular mechanism by which BCRP expression in human placental choriocarcinoma BeWo cells is regulated by progesterone. Transfection of the progesterone receptor (PR) isoforms PRA and PRB resulted in a similarly increased expression of PRA and PRB, respectively. However, progesterone significantly increased BCRP expression and activity only in PRB-transfected cells. This stimulatory effect of progesterone was abrogated by the PR antagonist mifepristone (RU-486). Consistently, transcriptional activity of the BCRP promoter was induced 2- to 6-fold by 10^-8 to 10^-5 M progesterone in PRB-transfected cells. Progesterone had little effect on BCRP expression and activity and transcriptional activity of the BCRP promoter in PRA-transfected cells; however, cotransfection of PRA and PRB significantly decreased the progesterone-response compared with that in cells transfected with only PRB. Mutations in a novel progesterone response element (PRE) identified between -243 to -115 bp of the BCRP promoter region significantly attenuated the progesterone-response in PRB-transfected cells, and deletion of the PRE nearly completely abrogated the progesterone effect. Specific binding of both PRA and PRB to the BCRP promoter through the identified PRE was confirmed using the electrophoretic mobility shift assay. Collectively, progesterone induces BCRP expression in BeWo cells via PRB but not PRA. PRA represses the PRB activity. Thus, PRA and PRB differentially regulate BCRP expression in BeWo cells.

Address correspondence to: Dr. Qingcheng Mao, Department of Pharmaceutics, School of Pharmacy, Box 357610, University of Washington, Seattle, WA 98195-7610. E-mail: qmao{at}u.washington.edu

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				M. Vore and M. Leggas Progesterone Acts via Progesterone Receptors A and B to Regulate Breast Cancer Resistance Protein Expression Mol. Pharmacol., March 1, 2008; 73(3): 613 - 615. [Abstract] [Full Text] [PDF]