Progesterone Receptor-B Induction of BIRC3 Protects Endometrial Cancer Cells from AP1-59-Mediated Apoptosis

Abstract

Progesterone is a growth inhibitory hormone in the endometrium. While progestins can be used for the treatment of well-differentiated endometrial cancers, resistance to progestin therapy occurs for reasons that remain unclear. We have previously demonstrated that progesterone receptors (PR) A and B differentially regulate apoptosis in response to overexpression of the forkhead transcription factor, FOXO1. In this study, we further examined the PR-isoform-dependent cellular response to the AKT pathway. Treatment of PRA and PRB-expressing Ishikawa cells (PRA14, PRB23), with an AKT inhibitor API-59CJ-OMe (API-59) promoted apoptosis in the presence and absence of the ligand, R5020 preferentially in PRA14 cells. Upon PR knockdown using small interfering RNA, an increase in apoptosis was observed in PRB23 cells treated with API-59 with or without R5020 while there was no influence in PRA14 cells. Using an apoptosis-focused real-time PCR array, genes regulated by API-59 and R5020 were identified both common and unique to PRA14 and PRB23 cells. BIRC3 was identified as the only gene regulated by R5020 which occurred only in PRB cells. Knockdown of BIRC3 in PRB23 cells promoted a decrease in cell viability in response to API-59 + R5020. Furthermore, the important role of inhibitors of apoptosis (IAPs) in the PRB23 cells to promote cell survival was demonstrated using an antagonist to IAPs, a second mitochondria-derived activator of caspase (Smac also known as DIABLO) mimetic. Treatment of PRB23 cells with Smac mimetic increased apoptosis in response to API-59 + R5020. In summary, our findings indicate a mechanism by which PRB can promote cell survival in the setting of high AKT activity in endometrial cancer cells.

Active FOXO1 Is a Key Determinant of Isoform-Specific Progesterone Receptor Transactivation and Senescence Programming

“…68 WISP1 binds to proteoglycans, decorin and biglycan, present in the extracellular matrix of connective tissues. 69 PR-B target genes BIRC3 (a mediator of cancer cell pro-survival and a well-characterized PR-B target gene in breast 66 and endometrial 70 cell models) and GZMA (a novel PR-B target gene identified herein and a mediator of cytotoxic T-cell responses significantly elevated in the serum of women with ovarian cancer 71 ) were robustly induced in PR-B-expressing clones (#1 and #3) relative to weak or insignificant induction in PR-A-expressing clones (#4 and #7) or controls (Figure 3B). Basal expression of BIRC3 noted in PR-A+ ES-2 pools (Figure 1B) validated in clonal PR-A-expressing clones (Figure 3B; #4 and #7 at 24 hr) and increased over time in untreated cells (compare vehicle-treated 24 to 96 hrs for each clone) but was primarily hormone-regulated in PR-B+ clones.…”

Critical Tumor Suppressor Function Mediated by Epithelial Mig-6 in Endometrial Cancer

“…Interestingly, apoptosis in sub-epithelial stroma cells of Wnt7a cre+ Mig-6 f/f mice was significantly increased compared to control mice at 3 months and 5 months of age (Figure 2, C and D). BIRC3 contributes to the survival of endometrial cancer cells against apoptosis mediated by inhibition of AKT (27). Therefore, it was determined whether Wnt7a cre+ Mig-6 f/f mice altered regulation of BIRC3 during endometrial hyperplasia development.…”

Roles of PI3K/AKT/GSK3/mTOR Pathway in Cell Signaling of Mental Illnesses

“…Inositol pentakisphosphate, one of the PI3K/AKT inhibitors, also inhibits tumor growth and angiogenesis. Several other AKT antagonists such as 9-methoxy-2-methylellipticinium acetate, indazole-pyridine A-443654, and isoform-specific canthine alkaloid analogs have also been identified and shown to inhibit cancer cell growth and induce apoptosis [53]. The mTOR inhibitors such as rapamycin and its analogs inhibit mTOR activation by binding to FK506-binding protein 12 [54].…”