Progesterone receptors induce FOXO1-dependent senescence in ovarian cancer cells

Abstract

Loss of nuclear progesterone receptors (PR) and low circulating progesterone levels are associated with increased ovarian cancer (OC) risk. However, PR are abundantly expressed in a significant percentage of serous and endometrioid ovarian tumors; patients with PR+ tumors typically experience longer progression-free survival relative to those with PR-null tumors. The molecular mechanisms of these protective effects are poorly understood. To study PR action in OC in the absence of added estrogen (i.e., needed to induce robust PR expression), we created ES-2 OC cells stably expressing vector control or GFP-tagged PR-B (GFP-PR). Progestin (R5020) stimulation of ES-2 cells stably expressing GFP-PR induced cellular senescence characterized by altered cellular morphology, prolonged survival, senescence-associated β-galactosidase activity, G1 cell cycle arrest and upregulation of the cell cycle inhibitor, p21, as well as the Forkhead-box transcription factor, FOXO1; these results repeated in unmodified ER+/PR+ PEO4 OC cells. PR-B and FOXO1 were detected within the same PRE-containing regions of the p21 upstream promoter. Knockdown of p21 resulted in molecular compensation via FOXO1-dependent upregulation of numerous FOXO1 target genes (p15, p16, p27) and an increased rate of senescence. Inhibition of FOXO1 (with AS1842856) or stable FOXO1 knockdown inhibited progestin-induced p21 expression and blocked progestin-induced senescence. Overall, these findings support a role for PR as a tumor suppressor in OC cells, which exhibits inhibitory effects by inducing FOXO1-dependent cellular senescence. Clinical "priming" of the PR-FOXO1-p21 signaling pathway using PR agonists may provide a useful strategy to induce irreversible cell cycle arrest and thereby sensitize OC cells to existing chemotherapies as part of combination "two-step" therapies.

Impact of levonorgestrel-releasing intrauterine system use on the cancer risk of the ovary and fallopian tube

“…Its risk has been reported not to be affected by oral contraceptives [16,17] but associations with HT use are inconsistent [7,17,18]. Progesterone receptor (PR) expression is lower in mucinous carcinomas than in other ovarian cancer subtypes [19] which may explain its resistance against the protective effect of oral contraceptives. Our finding of lower risk of both mucinous borderline ovarian tumors and mucinous carcinomas in the LNG-IUS users could be mediated by other mechanisms than direct progestin effect of LNG-IUS.…”

“…High grade serous tumors cause the majority of deaths due to ovarian cancer [25]. Low grade serous ovarian carcinoma is a more indolent type originating from serous borderline tumors and does express high levels of PR [19,22,25]. In this study, serous carcinomas were analyzed as one group because data of tumor grades were not available.…”

Targeting FoxO1 with AS1842856 Suppresses Adipogenesis

“…[23][24][25] We tested 0.1 mM and 1 mM, and found AS1842856 severely suppressed adipogenesis at both concentrations, thus choosing to use 0.1 mM for the treatments if not specified elsewhere. AS1842856 or the vehicle 0.1% DMSO as a treatment control was supplemented through the whole procedure of BMI!DMI!DMII!BMII (Fig.…”

“…23 It can potently inhibit the DNA binding of FoxO1 and its transactivation. [23][24][25] In hepatic cells, AS1842856 inhibits glucose production by suppressing G6P and PEPCK mRNA levels, and administration of AS1842856 to diabetic db/db mice significantly reduces fasting blood glucose. 23 However, the effect of AS1842856 on adipogenesis has not been examined.…”

RC-6 ribonuclease induces caspase activation, cellular senescence and neuron-like morphology in NT2 embryonal carcinoma cells

“…Thus, our results indicated that RC-6 can induce senescence characteristics in NT2 cells. Previous studies demonstrated that p27 protein increase was also found in senescence cells (49,68,69). However, p27 protein levels were not increased significantly in RC-6-treated NT2 cells.…”