Progesterone Enhances Calcitriol Antitumor Activity by Upregulating Vitamin D Receptor Expression and Promoting Apoptosis in Endometrial Cancer Cells

Abstract

Human studies suggest that progesterone and calcitriol may prove beneficial in preventing or inhibiting oncogenesis, but the underlying mechanism is not fully understood. The current study investigates the effects of progesterone, calcitriol, and their combination on immortalized human endometrial epithelial cells and endometrial cancer cells and identifies their targets of action. Combination treatment with both agents enhanced vitamin D receptor expression and inhibited cell proliferation through caspase-3 activation and induction of G 0 -G 1 cell-cycle arrest with associated downregulation of cyclins D1 and D3 and p27 induction. We used mass spectrometry-based proteomics to measure protein abundance differences between calcitriol-, progesterone-, or combination-exposed endometrial cells. A total of 117 proteins showed differential expression among these three treatments. Four proteins were then selected for validation studies: histone H1.4 (HIST1H1E), histidine triad nucleotide-binding protein 2 (HINT2), IFN-induced, double-stranded RNA-activated protein kinase (EIF2AK2), and Bcl-2-associated X protein (BAX). Abundance levels of selected candidates were low in endometrial cancer cell lines versus the immortalized endometrial epithelial cell line. All four proteins displayed elevated expression in cancer cells upon exposure to calcitriol, progesterone, or the combination. Further BAX analysis through gain-or loss-of-function experiments revealed that upregulation of BAX decreased cell proliferation by changing the BAX:BCL-2 ratio. Knockdown of BAX attenuated progesterone-and calcitriol-induced cell growth inhibition. Our results showed that progesterone and calcitriol upregulate the expression of BAX along with other apoptosis-related proteins, which induce inhibition of endometrial cancer cell growth by apoptosis and cell-cycle arrest. Cancer Prev Res; 6(7); 731-43. Ó2013 AACR.

Progesterone Inhibits Endometrial Cancer Invasiveness by Inhibiting the TGFβ Pathway

“…Because the findings reported herein suggest a role of progesterone in regulation of the TGFb/SMAD signaling pathway, it is conceivable that the response of cells to progesterone depends on progesterone receptors. In our recently published study (40), we have shown reduced expression of both isoforms (PR-A and PR-B) in cancer (Ishikawa, HEC-1B, and RL95-2) cell lines compared with an immortalized endometrial epithelial (EM-E6/E7-TERT) cell line, and no marked changes were noticed in the expression of progesterone receptor isoforms in immortalized cells and in endometrial cancer cells following progesterone treatment. Treatment of endometrial cancer cells with progesterone caused a dose-dependent decrease in cell viability, and progesterone receptor antagonist abrogated that effect (29), suggesting the presence of functional progesterone receptors on endometrial cancer cells.…”

“…In the previous study, we investigated the effects of progesterone on endometrial cancer cells and identified its targets of action using mass spectrometry-based proteomics. A total of 278 proteins, including histone H1.4 (HIST1H1E), histidine triad nucleotide-binding protein 2 (HINT2), IFNinduced, double-stranded RNA-activated protein kinase (EIF2AK2), and Bcl-2-associated X protein (BAX), showed differential expression with progesterone (40). The dominant inhibitory effect of progesterone on cell viability and invasion can be attributed to upregulation of several tumor suppressor proteins suppressing cancer cell viability and invasive potential independent of the TGFb signaling pathway.…”

Vitamin D and Endometrium: A Systematic Review of a Neglected Area of Research

“…Similar studies proposed VD as an anti-proliferative drug in endometrial cancer cell lines, mainly reporting a mechanism of growth arrest [30,58] or apoptosis [59,60]. Calcitriol treatment induced cell cycle arrest in endometrial cancer cells suppressing some regulators of the cell cycle progression such as cyclin D1 and D 3 and increasing the expression of p27, a well-known cell cycle inhibitor [59].…”

“…Calcitriol treatment induced cell cycle arrest in endometrial cancer cells suppressing some regulators of the cell cycle progression such as cyclin D1 and D 3 and increasing the expression of p27, a well-known cell cycle inhibitor [59]. In addition, other authors reported variations in expression of proteins involved in several molecular mechanisms such as apoptosis (ex.…”

Paclitaxel, Carboplatin and 1,25-D3 Inhibit Proliferation of Endometrial Cancer Cells In Vitro

“…1,25-D3 is responsible for VDR-mediated apoptosis and inhibits angiogenesis and differentiation in a variety of cancer types (13,(16)(17)(18)(19)(20). 1,25-D3 is a potential antitumor agent because of its ability to regulate cancer cell growth.…”