Progesterone receptor A and B expression and progestagen treatment in growth and spread of endometrial cancer cells in nude mice

Progesterone-Induced miR-145/miR-143 Inhibits the Proliferation of Endometrial Epithelial Cells

Our previous study showed that progesterone (P4) can specifically regulate the expression of some microRNAs (miRNAs) in endometrial epithelium. In the present study, we verified the P4-dependent expression of miR-145/miR-143 in endometrial epithelial cells, explored the regulative mechanism of the P4 receptor (PR), and investigated their effects on the proliferation of endometrial epithelial cells. Our results showed that P4 can induce the expression of miR-145/143 in endometrial epithelial cells by acting on the PR A subtype. P4-induced miR-145/143 can inhibit the expression of cyclin D2 by binding to cyclin D2 mRNA 3'UTR. It can also inhibit cell proliferation in mouse endometrial epithelium by arresting the cell cycle during the G1-S checkpoint. Furthermore, miR-145 and miR-143 can inhibit the proliferation of human endometrial cancer cells. In conclusion, P4-induced miR-145/miR-143 is an important regulator in the proliferation of endometrial epithelial cells, and it can also inhibit the proliferation of human endometrial cancer cells. Our study indicates miRNAs are important mechanism of P4 in inhibiting the proliferation of endometrial epithelial cells. And these miRNAs are potential candidates for the diagnosis of endometrial cancer and therapeutic targets.

Progesterone-induced miR-133a inhibits the proliferation of endometrial epithelial cells

AIM

This study aimed to understand the role of miR-133a in progesterone actions, explore the regulative mechanism of the progesterone receptor, and investigate the effects of miR-133a on the progesterone-inhibited proliferation of mouse endometrial epithelial cells.

METHODS

The expression of miR-133a induced by progesterone was detected by quantitative real-time PCR both in vivo and in vitro. Ishikawa subcell lines stably transfected with progesterone receptor subtypes were used to determine the receptor mechanism of progesterone inducing miR-133a. Specific miR-133a mimics or inhibitors were transfected into mouse uteri and primary cultured endometrial epithelial cells to overexpress or downregulate the miR-133a. The roles of miR-133a in the cell cycle and proliferation of endometrial epithelial cells were analysed by flow cytometry and Edu incorporation analysis. The protein levels of cyclinD2 in uterine tissue sections and primary cultured endometrial epithelial cells were determined by immunohistochemistry and Western blot analysis.

RESULTS

Progesterone could induce miR-133a expression in a PRB-dependent manner in endometrial epithelial cells. miR-133a inhibited endometrial epithelial cell proliferation by arresting cell cycle at the G₁ -S transition. Moreover, miR-133a acted as an inhibitor in downregulating cyclinD2 in endometrial epithelial cells.

CONCLUSION

We showed for the first time that progesterone-induced miR-133a inhibited the proliferation of endometrial epithelial cells by downregulating cyclinD2. Our research indicated an important mechanism for progesterone inhibiting the proliferation of endometrial epithelial cells by inducing special miRNAs to inhibit positive regulatory proteins in the cell cycle.

Progesterone-Induced miR-152 Inhibits the Proliferation of Endometrial Epithelial Cells by Downregulating WNT-1

Progesterone (P4) is an important ovarian hormone that inhibits estrogen-dependent proliferation of endometrial epithelial cells (EECs). miR-152 has been reported to be a cell cycle regulator. In this study, we first demonstrated that P4 induced the expression of miR-152 in ovariectomized mice and Ishikawa cell. miR-152 was detected in the human endometrial cell lines that were stably transfected with P4 receptor. Results showed that P4 induced its expression through its receptor B subtype. Then, using the specific miRNA mimic and inhibitor, we proved that miR-152 impeded G₁/S transition in the cell cycle of EECs and inhibited cellular proliferation via downregulating WNT-1 in mice and human endometrial cancer cell lines (Ishikawa, HEC-1-b, and KLE). miR-152 induced by P4 is an important inhibitor for the proliferation of EECs. miR-152 may be an important tumor suppressor microRNA in endometrial cancer.

Molecular profiling of estrogen receptor α and progesterone receptor transcript variants in endometrial cancer

The human genes coding for estrogen receptor alpha (ERα) and progesterone receptor (PR) express multiple receptor splice variants. Some of these receptor variants previously have been shown to exert distinct functions in cancer cells and might therefore differentially affect individual prognosis or therapy response. To examine the role of ERα- and PR-isoforms in endometrial cancer, we compared the expression of 19 ERα transcripts and 15 PR mRNA isoforms in human endometrium and in endometrioid endometrial cancer. Expression of seven ERα splice variants, total PR and of five PR transcript isoforms was found to be significantly decreased in endometrial cancer. In endometrioid G3 tumors, expression of 17 ERα and 10 PR splice variants was reduced when compared to normal tissue. Notably, only 13% of G3 tumors did not express any ERα variant and only in 25% of G3 samples no PR transcripts were expressed. Seven splice variants were preferentially expressed in G1 and G2 tumors. In G1 tumors, a higher number of different ERα and PR splice variants was expressed than in normal endometrium, G2 or G3 tumors. Expression of total PR and of single PR splice variants was found to be positively associated with PTEN. Our results encourage further studies to elucidate to what extent the heterogeneous co-expression profiles we found in endometrial cancer patients differentially affect both individual prognosis and therapy response.

Progesterone receptor membrane component 1 deficiency attenuates growth while promoting chemosensitivity of human endometrial xenograft tumors

Endometrial cancer is the leading gynecologic cancer in women in the United States with 52,630 women predicted to be diagnosed with the disease in 2014. The objective of this study was to determine if progesterone (P4) receptor membrane component 1 (PGRMC1) influenced endometrial cancer cell viability in response to chemotherapy in vitro and in vivo. A lentiviral-based shRNA knockdown approach was used to generate stable PGRMC1-intact and PGRMC1-deplete Ishikawa endometrial cancer cell lines that also lacked expression of the classical progesterone receptor (PGR). Progesterone treatment inhibited mitosis of PGRMC1-intact, but not PGRMC1-deplete cells, suggesting that PGRMC1 mediates the anti-mitotic actions of P4. To test the hypothesis that PGRMC1 attenuates chemotherapy-induced apoptosis, PGRMC1-intact and PGRMC1-deplete cells were treated in vitro with vehicle, P4 (1 µM), doxorubicin (Dox, 2 µg/ml), or P4 + Dox for 48 h. Doxorubicin treatment of PGRMC1-intact cells resulted in a significant increase in cell death; however, co-treatment with P4 significantly attenuated Dox-induced cell death. This response to P4 was lost in PGRMC1-deplete cells. To extend these observations in vivo, a xenograft model was employed where PGRMC1-intact and PGRMC1-deplete endometrial tumors were generated following subcutaneous and intraperitoneal inoculation of immunocompromised NOD/SCID and nude mice, respectively. Tumors derived from PGRMC1-deplete cells grew slower than tumors from PGRMC1-intact cells. Mice harboring endometrial tumors were then given three treatments of vehicle (1:1 cremophor EL: ethanol + 0.9% saline) or chemotherapy [Paclitaxel (15 mg/kg, i.p.) followed after an interval of 30 minutes by CARBOplatin (50 mg/kg)] at five day intervals. In response to chemotherapy, tumor volume decreased approximately four-fold more in PGRMC1-deplete tumors when compared with PGRMC1-intact control tumors, suggesting that PGRMC1 promotes tumor cell viability during chemotherapeutic stress. In sum, these in vitro and in vivo findings demonstrate that PGRMC1 plays a prominent role in the growth and chemoresistance of human endometrial tumors.

Endometrial miR-181a and miR-98 expression is altered during transition from normal into cancerous state and target PGR, PGRMC1, CYP19A1, DDX3X, and TIMP3

CONTEXT

Evidence suggests that a number of microRNA (miRNA) are aberrantly expressed in endometrial disorders with potential posttranscriptional regulation of their specific target genes, including ovarian steroid receptors.

OBJECTIVES

Our objective was to assess the endometrial expression of miR-98 and miR-181a and their respective target genes, progesterone (P4) receptor membrane component 1 (PGRMC1) and P4 receptor (PGR).

DESIGN, SETTING, AND PATIENTS

We evaluated tissue expression and in vitro regulation at an academic university medical center in endometrial biopsies and endometrial tissues from follicular and luteal phases with and without exposure to hormonal therapies and grade I-III endometrial cancer (n = 52).

INTERVENTIONS

INTERVENTIONS included endometrial biopsies and in vitro transfection.

MAIN OUTCOME MEASURES

We evaluated expression and function of miR-98 and miR-181a.

RESULTS

Aberrant expression of miR-98 and miR-181a is associated with endometrial transition from normal into cancerous states, which to some extent is influenced by hormonal milieu, and exhibited an inverse relationship with PGMRC1 and PGR expression, respectively. Treatments of Ishikawa cells with 17β-estradiol, P4, or medroxyprogesterone acetate had limited effects on miR-98, miR-181a, and PGRMC1 expression, whereas 17β-estradiol treatment increased PGR expression. In Ishikawa cells, gain of function of miR-98 repressed PGRMC1 and CYP19A1, and miR-181a repressed PGR, DDX3X, and TIMP3 at mRNA and protein levels through direct interactions with their respective 3'-untranslated regions and CCNE1 through miR-181a-induced DDX3X repression, with miR-98 reducing the rate of cell proliferation as compared with controls.

CONCLUSION

miR-98 and miR-181a through their regulatory functions on PGRMC1, PGR, CYP19A1, TIMP3, and DDX3X expression may influence a wide range of endometrial cellular activities during normal menstrual cycle and transition into disease states, including endometrial cancer.

Progesterone receptor-B induction of BIRC3 protects endometrial cancer cells from AP1-59-mediated apoptosis

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.

Role of progesterone in endometrial cancer

Progesterone is a key hormone in the endometrium that opposes estrogen-driven growth. Insufficient progesterone will result in unopposed estrogen action that could lead to the development of endometrial hyperplasia and adenocarcinoma. Although these endometrial neoplasias can regress in response to progestin treatment, this does not occur in all instances. To understand this resistance to progesterone and to improve on existing hormonal therapies, it is imperative that the molecular mechanisms of progesterone action through its receptor be deciphered in endometrial cancer. This review highlights what is known thus far regarding the efficacy of progestin therapy in the clinic and the role of progesterone in endometrial cancer cell behavior and gene regulation.

Progesterone receptor action in leiomyoma and endometrial cancer

Progesterone is a key hormone in the regulation of uterine function. In the normal physiological context, progesterone is primarily involved in remodeling of the endometrium and maintaining a quiescent myometrium. When pathologies of the uterus develop, specifically, endometrial cancer and uterine leiomyoma, response to progesterone is usually altered. Progesterone acts through mainly two isoforms of the progesterone receptor (PR), PRA and PRB which have been reported to exhibit different transcriptional activities. Studies examining the expression and function of the PRs in the normal endometrium and myometrium as well as in endometrial cancer and uterine leiomyoma are summarized here. The clinical use of progestins and the transcriptional activity of the PR on genes specific to endometrial cancer and leiomyoma are described. An increased understanding of the differential expression of PRs and response to progesterone in these two diseases is critical in order to develop more efficient and targeted therapies.

Ultrastructural localization of extranuclear progestin receptors in the rat hippocampal formation

Progesterone's effects on hippocampus-dependent behavior and synaptic connectivity maybe mediated through the progestin receptor (PR). Although estrogen induces PR mRNA and cytosolic PR in the hippocampus, nuclear PR immunoreactivity is undetectable by light microscopy, suggesting that PR is present at extranuclear sites. To determine whether this is the case, we used immunoelectron microscopy to examine PR distribution in the hippocampal formation of proestrus rats. Ultrastructural analysis revealed that PR labeling is present in extranuclear profiles throughout the CA1 and CA3 regions and dentate gyrus, and, in contrast to light microscopic findings, in nuclei of a few pyramidal and subgranular zone cells. Most neuronal PR labeling is extranuclear and is divided between pre- and postsynaptic compartments; approximately 30% of labeled profiles were axon terminals and 30% were dendrites and dendritic spines. In most laminae, except in CA3 stratum lucidum, about 15% of PR-immunoreactive profiles were unmyelinated axons. In stratum lucidum, where the mossy fiber axons course, more than 50% of PR-labeled profiles were axonal. The remaining 25% of PR-labeled profiles were glia, some resembling astrocytes. PR labeling is strongly dependent on estrogen priming, insofar as few PR-labeled profiles were detected in ovariectomized, oil-replaced females. Synapses formed by PR-labeled terminals were predominantly asymmetric, consistent with a role for progesterone in directly regulating excitatory transmission. These findings suggest that some of progesterone's actions in the hippocampal formation may be mediated by direct and rapid actions on extranuclear PRs and that PRs are well positioned to regulate progesterone-induced changes at synapses.

The regulation and function of the forkhead transcription factor, Forkhead box O1, is dependent on the progesterone receptor in endometrial carcinoma

In many type I endometrial cancers, the PTEN gene is inactivated, which ultimately leads to constitutively active Akt and the inhibition of Forkhead box O1 (FOXO1), a member of the FOXO subfamily of Forkhead/winged helix family of transcription factors. The expression, regulation, and function of FOXO1 in endometrial cancer were investigated in this study. Immunohistochemical analysis of 49 endometrial tumor tissues revealed a decrease of FOXO1 expression in 95.9% of the cases compared with the expression in normal endometrium. In four different endometrial cancer cell lines (ECC1, Hec1B, Ishikawa, and RL95), FOXO1 mRNA was expressed at similar levels; however, protein levels were low or undetectable in Ecc1, Ishikawa, and RL95 cells. Using small interfering RNA technology, we demonstrated that the low levels of FOXO1 protein were due to the involvement of Skp2, an oncogenic subunit of the Skp1/Cul1/F-box protein ubiquitin complex, given that silencing Skp2 increased FOXO1 protein expression in Ishikawa cells. Inhibition of Akt in Ishikawa cells also increased nuclear FOXO1 protein levels. Additionally, progestins increased FOXO1 protein levels, specifically through progesterone receptor B (PRB) as determined by using stably transfected PRA-specific and PRB-specific Ishikawa cell lines. Finally, overexpression of triple mutant (Tm) FOXO1 in the PR-specific Ishikawa cell lines caused cell cycle arrest and significantly decreased proliferation in the presence and absence of the progestin, R5020. Furthermore, TmFOXO1 overexpression induced apoptosis in PRB-specific cells in the presence and absence of ligand. Taken together, these data provide insight into the phosphoinositide-3-kinase/Akt/FOXO pathway for the determination of progestin responsiveness and the development of alternate therapies for endometrial cancer.

Hormonal heterogeneity of endometrial cancer

Endometrial cancer is the most common malignant tumor of the female genital tract in the developed world. Increasing evidence suggests that the majority of cases can be divided into two different types ofendometrial cancer based on clinico-pathological and molecular characteristics. Type I is associated with an endocrine milieu of estrogen predominance. These tumors are ofendometroid histology and develop from endometrial hyperplasia. They have good prognosis and are sensitive to endocrine treatment. Type II endometrial cancers are not associated with a history of unopposed estrogens and develop from the atrophic endometrium of elderly women. Mainly, they are of serous papillary or clear cell morphology, have a poor prognosis and do not react to endocrine treatment. Both types of endometrial cancer probably differ markedly with regard to the molecular mechanisms of transformation. The transition from normal endometrium to a malignant tumor is thought to involve a stepwise accumulation of alterations in cellular mechanisms leading to dysfunctional cell growth. This chapter reviews the current knowledge of the molecular mechanisms commonly associated with development of type I and type II endometrial cancer.

Krüppel-Like Factor 9 Is a Negative Regulator of Ligand-Dependent Estrogen Receptor α Signaling in Ishikawa Endometrial Adenocarcinoma Cells

Estrogen and progesterone, acting through their respective receptors and other nuclear proteins, exhibit opposing activities in target cells. We previously reported that Krüppel-like factor 9 (KLF9) cooperates with progesterone receptor (PR) to facilitate P-dependent gene transcription in uterine epithelial cells. Here we evaluated whether KLF9 may further support PR function by directly opposing estrogen receptor (ER) signaling. Using human Ishikawa endometrial epithelial cells, we showed that 17β-estradiol (E2)-dependent down-regulation of ERα expression was reversed by a small interfering RNA to KLF9. Transcription assays with the E2-sensitive 4× estrogen-responsive element-thymidine kinase-promoter-luciferase reporter gene demonstrated inhibition of ligand-dependent ERα transactivation with ectopic KLF9 expression. E2 induced PR-A/B and PR-B isoform expression in the absence of effects on KLF9 levels. Addition of KLF9 small interfering RNA augmented E2 induction of PR-A/B while abrogating that of PR-B, indicating selective E2-mediated inhibition of PR-A by KLF9. Chromatin immunoprecipitation of the ERα minimal promoter demonstrated KLF9 promotion of E2-dependent ERα association to a region containing functional GC-rich motifs. KLF9 inhibited the recruitment of the ERα coactivator specificity protein 1 (Sp1) to the PR proximal promoter region containing a half-estrogen responsive element and GC-rich sites, but had no effect on Sp1 association to the PR distal promoter region containing GC-rich sequences. In vivo association of KLF9 and Sp1, but not of ERα with KLF9 or Sp1, was observed in control and E2-treated cells. Our data identify KLF9 as a transcriptional repressor of ERα signaling and suggest that it may function at the node of PR and ER genomic pathways to influence cell proliferation.

Epidermal growth factor receptor signaling enhanced by long-term medroxyprogesterone acetate treatment in endometrial carcinoma

OBJECTIVE

Progestin is an effective endocrine treatment for patients with atypical hyperplasia or with endometrial carcinoma that is estrogen receptor (ER) positive and progesterone receptor (PR) positive. However, long-term progestin treatment may lead to resistance. We have studied the progestin resistance phenotype that frequently develops in endometrial carcinoma.

METHODS

Ishikawa endometrial carcinoma cells were cultured for a long period (10 months) in the presence of the synthetic progestin medroxyprogesterone acetate (MPA), thereby generating a subline refractory to the growth-suppressive effects of MPA.

RESULTS

The MPA-resistant subline showed growth stimulation rather than inhibition after MPA treatment. Immunocytochemical analysis showed reduced ER alpha and PR-B expression and increased ER beta expression in this subline compared with parental Ishikawa cells. Progestin-resistant Ishikawa cells also showed increased expression of transforming growth factor alpha (TGFalpha), the epidermal growth factor receptor (EGFR), and EGFR tyrosine kinase (EGFR-TK); MPA treatment further stimulated the expression of TGFalpha in these cells. Additionally, progestin-resistant Ishikawa cells were highly sensitive to growth stimulation by TGFalpha and to growth inhibition by the EGFR-TK-specific inhibitor AG1478, and they showed increased dependence on TGFalpha-EGFR signaling.

CONCLUSIONS

Our results suggest that prolonged treatment of endometrial carcinoma cells with MPA induces resistance to the growth-suppressive effects of MPA and enhances cancer cell proliferation. The downregulation of ER alpha and PR-B, the upregulation of ER beta, and highly activated TGF-EGFR signaling are thus likely to contribute to progestin resistance in endometrial carcinoma. Therefore, an EGFR-TK-specific inhibitor might be useful in the treatment of progestin-resistant endometrial carcinoma.