Abstract 846: Progesterone receptor membrane component 1 controls cellular proliferation and plays a key role in the molecular circuitry of both ER positive and triple negative breast cancers

Abstract

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. The basis of the signaling mechanisms of progesterone membrane receptors remain largely unknown. Both the nuclear and membrane progesterone receptors could play a significant role in the development and progression of breast cancers and both could become viable therapeutic options. We, aim to investigate the molecular circuitry of PGRMC1 in both ER-positive and Triple Negative Breast Cancers (TNBCs). Materials and Methods: Human breast tissues were utilized to identify the expression of PGRMC1 along with a panel of normal and breast cancer cell lines. PGRMC1 overexpressing ZR-75-1 and MDA-MB-468 breast cancer cell lines were selected and treated with AG-205 (PGRMC1 inhibitor) and PGRMC1 siRNAs, while PGRMC1 was overexpressed in MCF10A non-malignant breast epithelial cells. MTS, qRT-PCR, Western blot, immunofluorescence, immunohistochemistry and flow cytometry were performed to study cell proliferation, apoptosis and key markers involved in these processes. In silico analysis utilizing publicly available gene expression datasets were also performed. Results: Immunohistochemistry demonstrated strong staining for PGRMC1 in human breast cancer tissue compared to normal breast 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. Both AG-205 and PGRMC1 targeted siRNAs decreased cell proliferation in ZR-75-1 and MDA-MB-468. Minimal effects of AG-205 were observed in MCF10A non-malignant breast epithelial cells. AG-205 treatment and silencing of PGRMC1 induced apoptosis in both cancer cell lines. Furthermore, PGRMC1 overexpression transformed MCF10A cells into a malignant phenotype. Key markers of cell proliferation (pAKT, CCND1, pEGFR, pmTOR) and apoptosis (PTEN, Bcl2, Bax,) revealed that PGRMC1 inhibition decreases proliferation while overexpression promotes tumorigenesis. Conclusion: Our data demonstrates that PGRMC1 plays a prominent role in both ER-positive and TNBCs. These initial findings uncover the potential of PGRMC1 as an oncogene and therapeutic target for breast cancer patients who overexpress this gene. Citation Format: Diego A. Pedroza, Ramadevi Subramani Reddy, Adriana Galvez, Rajkumar Lakshmanaswamy. Progesterone receptor membrane component 1 controls cellular proliferation and plays a key role in the molecular circuitry of both ER positive and triple negative breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 846.