Progesterone receptor blockade in human breast cancer cells decreases cell cycle progression through G2/M by repressing G2/M genes

Abstract

BackgroundThe synthesis of specific, potent progesterone antagonists adds potential agents to the breast cancer prevention and treatment armamentarium. The identification of individuals who will benefit from these agents will be a critical factor for their clinical success.MethodsWe utilized telapristone acetate (TPA; CDB-4124) to understand the effects of progesterone receptor (PR) blockade on proliferation, apoptosis, promoter binding, cell cycle progression, and gene expression. We then identified a set of genes that overlap with human breast luteal-phase expressed genes and signify progesterone activity in both normal breast cells and breast cancer cell lines.ResultsTPA administration to T47D cells results in a 30 % decrease in cell number at 24 h, which is maintained over 72 h only in the presence of estradiol. Blockade of progesterone signaling by TPA for 24 h results in fewer cells in G2/M, attributable to decreased expression of genes that facilitate the G2/M transition. Gene expression data suggest that TPA affects several mechanisms that progesterone utilizes to control gene expression, including specific post-translational modifications, and nucleosomal organization and higher order chromatin structure, which regulate access of PR to its DNA binding sites.ConclusionsBy comparing genes induced by the progestin R5020 in T47D cells with those increased in the luteal-phase normal breast, we have identified a set of genes that predict functional progesterone signaling in tissue. These data will facilitate an understanding of the ways in which drugs such as TPA may be utilized for the prevention, and possibly the therapy, of human breast cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2355-5) contains supplementary material, which is available to authorized users.

Rapid reversible changes in compartments and local chromatin organization revealed by hyperosmotic shock

“…Cell culture T47D cells were grown for 48 h with RPMI containing charcoaltreated FBS as described previously (Reyes et al 2014;Clare et al 2016). Cells were then switched to a medium without serum (288 mOsm) for 18 h prior to treatment.…”

“…Thus, an increase of osmolarity has a rapid strong effect on chromatin organization. To assess chromosome organization, we harvested T47D cells that were maintained in isotonic medium or were exposed to mild hyperosmotic stress (110 mM NaCl) for 1 h, and performed in situ Hi-C. We used arrested T47D cells to eliminate possible effects of stress on cell cycle progression that could lead to indirect differences in chromosome organization (Reyes et al 2014;Clare et al 2016;Nagano et al 2017). Of note, exposure to mild hyperosmolarity did not affect cell viability even at higher NaCl doses (up to 200 mM) and a longer exposure (Supplemental Fig.…”

Selective Progesterone Receptor Modulators in Early-Stage Breast Cancer: A Randomized, Placebo-Controlled Phase II Window-of-Opportunity Trial Using Telapristone Acetate

“…Activated PR is a context-dependent mitogen in these cancers and it is known that PR independently governs estrogen action and breast cancer biology (3)(4)(5). We and others have previously reported that selective progesterone receptor modulators (SPRMs) inhibit proliferation of PR-positive breast cancer cell lines and suppress rodent mammary tumor formation in a progestin-rich environment (6)(7)(8)(9)(10). In addition, mifepristone (RU486) reduces proliferation in normal breast tissue (11), and progestin exposure contributes to higher breast cancer risk in postmenopausal women (12).…”

A Way Forward for Cancer Chemoprevention: Think Local

“…Telapristone is a selective progesterone modulator (SPRM), and we have implemented a chemoprevention trial of LTT to the breast (ClinicalTrials.gov: NCT02314156). As a SPRM, telapristone leads to progesterone receptor blockade leading to changes in gene expression and deceasing progression of a mutated cell through the cell-cycle progression (69). In preclinical testing, topical telapristone has been studied in comparison with systemic telapristone delivered subcutaneously in a multi-arm trial involving athymic nude rats with primary focus on tissue and plasma concentrations (70).…”