Abstract P5-05-12: Progesterone drives ER-positive and triple negative breast cancer cell proliferation through progesterone receptor membrane component 1
Authors: Pedroza DA , Subramani R , Galvez A , Lakshmanaswamy R 
Published: May 2019

Abstract
Introduction: The role of progesterone and its receptors in breast cancer progression continue to be studied but remain controversial. Progesterone membrane receptors with the ability to regulate kinase signals, mediating breast cancer proliferation have been demonstrated. Increased expression of the Progesterone Receptor Membrane Component 1 (PGRMC1), a heme – binding protein with the ability to interact and stabilize epidermal growth factor receptor (EGFR) is frequently found in breast cancer tissue. Some evidence suggests that progesterone can stimulate and regulate breast cancer cell proliferation. The basis of the signaling mechanisms by which Progesterone exerts its function remains largely unknown. Both the nuclear and membrane progesterone receptors could play a significant role in the development and progression of breast cancer and both could become viable therapeutic options. We, aim to investigate the role of PGRMC1 in progesterone driven breast cancers.
Materials and Methods: Human breast tissues were utilized to identify PGRMC1 expression along with a panel of normal and breast cancer cell lines. Two breast cancer cell lines (ZR-75-1 and MDA-MB-468) were selected and treated with progesterone and AG-205 (PGRMC1 inhibitor) at different concentrations to assess optimum dosage. We performed MTS assay, qRT-PCR, Western blot, immunofluorescence, immunohistochemistry and flow cytometry for measuring cell proliferation, apoptosis and key markers involved in these processes. We also performed an in silico analysis to compare the expression of PGRMC1 in various cell lines and breast cancer tissues.
Results: Immunohistochemistry demonstrated strong staining for PGRMC1 in human breast cancer tissue compared to normal tissue. Increased PGRMC1 expression was observed specifically in ZR-75-1 and MDA-MB-468 cells by qRT-PCR, western blot and immunofluorescence, these results were validated and compared to microarray-based gene expression analysis of breast cell lines and breast tumor data sets. Progesterone treatment increased cell proliferation in a dose dependent manner while AG-205 decreased cell proliferation in a dose dependent manner in ZR-75-1 and MDA-MB-468. Minimal effects of AG-205 were observed in normal breast epithelial cells. AG-205 also, induced apoptosis in both ZR-75-1 and MDA-MB-468 cell lines. Furthermore, short-term treatment of progesterone increased both mRNA and protein expression of PGRMC1. Key markers of cell proliferation (pAKT, CCND1, pEGFR, pmTOR) and apoptosis (PTEN, Bcl2, Bax, Bim) revealed that PGRMC1 facilitated the proliferative effect of progesterone. Interestingly progesterone increases phosphorylation of EGFR and treatment of AG-205 alters EGFR expression in a dose dependent manner.
Conclusion: Our data demonstrates that PGRMC1 plays a prominent role in regulating progesterone driven cell proliferation in both ER-positive and triple negative breast cancer cells. These initial findings uncover the potential of PGRMC1 as a therapeutic target for breast cancers.
Citation Format: Pedroza DA, Subramani R, Galvez A, Lakshmanaswamy R. Progesterone drives ER-positive and triple negative breast cancer cell proliferation through progesterone receptor membrane component 1 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-12.