Abstract B58: Progesterone receptor (PR) isoforms drive distinct cell-cell interactions and gene expression programs in human fallopian tube models of early HGSOC

Abstract

Abstract High-grade serous ovarian carcinoma (HGSOC), the most prevalent and aggressive form of ovarian cancer (OC), contains abundant receptors for the ovarian steroid hormones, estrogen (ER; 76%) and progesterone (PR; 35%). These receptors contribute to the development of breast and reproductive tract cancers via complex mechanisms. Estrogen, acting through ERalpha, is well accepted as a stimulatory hormone while progesterone is thought to be a protective factor that reduces OC risk. Our understanding, however, of the molecular and cell-type specific mechanisms of PR isoform action in the initiation and progression of OC is limited. Therefore, to investigate altered PR isoform signaling in early-stage HGSOC, we utilized p53-dominant negative mutant fallopian tube epithelial (FTE) cells to generate stable cell lines expressing either PR-A or PR-B. Progestin (R5020) treatment of 2D adherent cultures revealed functional PR signaling through MAPK-dependent PR S294 phosphorylation as well as isoform specific expression of PR target genes encoding adhesion molecules (e.g., HEF1), cell cycle regulators (e.g., FOXO1), and glucocorticoid signaling proteins (e.g., CRISPLD2, NDRG1). In order to mimic early dissemination of FTE cells from serous tubal intraepithelial carcinoma (STIC) lesions, a precursor for the majority of HGSOCs, we established a 3D spheroid culture model. Interestingly, we observed that PR expression greatly increased the formation, size, and number of total spheroids compared to PR-negative controls. Progestin treatment resulted in additional enhancement of spheroid size with distinct morphologic differences observed between PR-A and PR-B expressing lines. Furthermore, progestin-treated cells grown as 3D spheroids exhibited increased basal PR protein and PR S294 phosphorylation levels relative to cells maintained in 2D adherent cultures, suggesting that hyperactivation of PRs occurs via cell-cell interactions, in part conferred by 3D architecture. Both PR-A and PR-B spheroids secreted matrix proteins such as fibronectin and other EMT biomarkers (e.g., integrin alpha 5) and progestin treatment modulated the PR isoform-specific expression of these markers. Preliminary RNA-seq analyses, comparing PR-A and PR-B spheroids, revealed differential expression of genes encoding pathways that regulate cell adhesion and cell movement as well as cytokine signaling and cell metabolism. Our results highlight the importance of cell context in understanding PR action and suggest that activation of PR signaling promotes and enhances the formation of nonadherent 3D structures in an isoform-specific manner. Such effects of progesterone are predicted to influence the shedding, aggregation, and dissemination of early FTE lesions. These preliminary findings demonstrate the importance of understanding the impact of steroid hormone receptors, including PR isoforms, on early OC development. Citation Format: Megan I. Seibel, Angela Spartz, Nuri Temiz, Laura J. Mauro, Carol A. Lange. Progesterone receptor (PR) isoforms drive distinct cell-cell interactions and gene expression programs in human fallopian tube models of early HGSOC. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr B58.