Effects of progesterone on ovarian tumorigenesis in xenografted mice

An HMGA2-p62-ERα axis regulates uterine leiomyomas proliferation

Uterine leiomyomas (ULM) are a major public health issue contributing to high morbidity and poor pregnancy outcomes. However, its molecular pathogenesis is poorly understood. HMGA2-ULM is the second major subtype of human ULM and associates with large sizes, fast-growth, and high percentages of estrogen receptor α (ERα). As altered ERα expression plays a distinct role in ULM growth, here, we investigate a regulatory mechanism driving ULM growth via HMGA2 and ERα. We reveal a positive correlation of HMGA2 with ERα protein and demonstrate that HMGA2 promotes ULM cells proliferation via ERα. In addition, autophagy pathway and p62/SQSTM1 (a selective autophagy receptor) are found to participate in the regulation of HMGA2 and ERα. Moreover, HMGA2 suppresses the transcription of p62 by binding to its promoter, meanwhile, p62 interacts with ERα, and inhibition of p62 increases ERα expression and enhances cell viability in ULM, suggesting a novel mechanism of the HMGA2-p62-ERα axis in ULM proliferation. Notably, rapamycin, a familiar autophagy agonist, reduces ERα levels and the proliferation ability of ULM cells. This study demonstrates a causal role of the HMGA2-p62-ERα axis in preventing autophagy and increasing ERα expression in HMGA2-ULM. Therefore, blocking HMGA2-p62-ERα axis and targeting autophagy pathway establish a roadmap toward HMGA2-ULM medical treatment.

Protective Effect of Progesterone during Pregnancy against Ovarian Cancer

There have been several epidemiologic studies supporting the protective role of pregnancy, although the mechanism is not clear. High level of progesterone, which is crucial in maintaining pregnancy, has been supposed to be one of the causative factors. Progesterone is produced at the corpus luteum in the early pregnancy and the placenta in the late pregnancy period. In several experimental studies, progesterone was reported to induce apoptosis of ovarian cancer cells through intrinsic and extrinsic pathways. In addition, progesterone has been shown to exert its anticancer effect through genomic and non-genomic action. The objective of this review is to discuss the protective mechanism of pregnancy against ovarian cancer focusing on the steroid hormone, progesterone.

Role of stem cells in human uterine leiomyoma growth

Background

Uterine leiomyoma is the most common benign tumor in reproductive-age women. Each leiomyoma is thought to be a benign monoclonal tumor arising from a single transformed myometrial smooth muscle cell; however, it is not known what leiomyoma cell type is responsible for tumor growth. Thus, we tested the hypothesis that a distinct stem/reservoir cell-enriched population, designated as the leiomyoma-derived side population (LMSP), is responsible for cell proliferation and tumor growth.

Principal Findings

LMSP comprised approximately 1% of all leiomyoma and 2% of all myometrium-derived cells. All LMSP and leiomyoma-derived main population (LMMP) but none of the side or main population cells isolated from adjacent myometrium carried a mediator complex subunit 12 mutation, a genetic marker of neoplastic transformation. Messenger RNA levels for estrogen receptor-α, progesterone receptor and smooth muscle cell markers were barely detectable and significantly lower in the LMSP compared with the LMMP. LMSP alone did not attach or survive in monolayer culture in the presence or absence of estradiol and progestin, whereas LMMP readily grew under these conditions. LMSP did attach and survive when directly mixed with unsorted myometrial cells in monolayer culture. After resorting and reculturing, LMSP gained full potential of proliferation. Intriguingly, xenografts comprised of LMSP and unsorted myometrial smooth muscle cells grew into relatively large tumors (3.67±1.07 mm³), whereas xenografts comprised of LMMP and unsorted myometrial smooth muscle cells produced smaller tumors (0.54±0.20 mm³, p<0.05, n = 10 paired patient samples). LMSP xenografts displayed significantly higher proliferative activity compared with LMMP xenografts (p<0.05).

Conclusions

Our data suggest that LMSP, which have stem/reservoir cell characteristics, are necessary for in vivo growth of leiomyoma xenograft tumors. Lower estrogen and progesterone receptor levels in LMSP suggests an indirect paracrine effect of steroid hormones on stem cells via the mature neighboring cells.

Progesterone signaling mediated through progesterone receptor membrane component-1 in ovarian cells with special emphasis on ovarian cancer

Various ovarian cell types including granulosa cells and ovarian surface epithelial cells express the progesterone (P4) binding protein, progesterone receptor membrane component-1 (PGRMC1). PGRMC1 is also expressed in ovarian tumors. PGRMC1 plays an essential role in promoting the survival of both normal and cancerous ovarian cell in vitro. Given the clinical significance of factors that regulate the viability of ovarian cancer, this review will focus on the role of PGRMC1 in ovarian cancer, while drawing insights into the mechanism of PGRMC1's action from cell lines derived from healthy ovaries as well as ovarian tumors. Studies using PGRMC1siRNA demonstrated that P4's ability to inhibit ovarian cells from undergoing apoptosis in vitro is dependent on PGRMC1. To confirm the importance of PGRMC1, the ability of PGRMC1-deplete ovarian cancer cell lines to form tumors in intact nude mice was assessed. Compared to PGRMC1-expressing ovarian cancer cells, PGRMC1-deplete ovarian cancer cells formed tumors in fewer mice (80% compared to 100% for controls). Moreover, the number of tumors derived from PGRMC1-deplete ovarian cancer cells was 50% of that observed in controls. Finally, the tumors that formed from PGRMC1-deplete ovarian cancer cells were about a fourth the size of tumors derived from ovarian cancer cells with normal levels of PGRMC1. One reason for PGRMC1-deplete tumors being smaller is that they had a poorly developed microvasculature system. How PGRMC1 regulates cell viability and in turn tumor growth is not known but part of the mechanism likely involves the regulation of genes that promote cell survival and inhibit apoptosis.

Progesterone is essential for maintenance and growth of uterine leiomyoma

Uterine leiomyomata (ULs) represent the most common tumor in women and can cause abnormal uterine bleeding, large pelvic masses, and recurrent pregnancy loss. Although the dependency of UL growth on ovarian steroids is well established, the relative contributions of 17beta-estradiol and progesterone are yet to be clarified. Conventionally, estradiol has been considered the primary stimulus for UL growth, and studies with cell culture and animal models support this concept. In contrast, no research model has clearly demonstrated a requirement of progesterone in UL growth despite accumulating clinical evidence for the essential role of progesterone in this tumor. To elucidate the functions of ovarian steroids in UL, we established a xenograft model reflecting characteristics of these tumors by grafting human UL tissue beneath the renal capsule of immunodeficient mice. Leiomyoma xenografts increased in size in response to estradiol plus progesterone through cell proliferation and volume increase in cellular and extracellular components. The xenograft growth induced by estradiol plus progesterone was blocked by the antiprogestin RU486. Furthermore, the volume of established UL xenografts decreased significantly after progesterone withdrawal. Surprisingly, treatment with estradiol alone neither increased nor maintained the tumor size. Although not mitogenic by itself, estradiol induced expression of progesterone receptor and supported progesterone action on leiomyoma xenografts. Taken together, our findings define that volume maintenance and growth of human UL are progesterone dependent.

Progesterone receptor membrane component-1 regulates the development and Cisplatin sensitivity of human ovarian tumors in athymic nude mice

To determine whether progesterone receptor membrane component 1 (PGRMC1) regulates the development and cisplatin (CDDP)-sensitivity of human ovarian tumors, PGRMC1 was depleted from a human ovarian cancer cell line, dsRed-SKOV-3 cells, using a short hairpin RNA knockdown approach. Compared with parental dsRed-SKOV-3 cells, the PGRMC1-deplete cells grew slower in vitro and did not show progesterone's (P4) antiapoptotic effect. In fact, P4 induced apoptosis in PGRMC1-deplete cells in a dose-dependent manner. When transplanted into the peritoneum of athymic nude mice, parental dsRed-SKOV-3 cells developed numerous tumors, which were classified as either typical or oxyphilic clear cell tumors. CDDP increased the percentage of apoptotic nuclei in typical clear cell tumors and P4 attenuated CDDP-induced apoptosis. In contrast, the percentage of apoptotic nuclei in oxyphilic clear cell tumors was low (< or =1%) and was not significantly affected by CDDP and/or P4. Compared with tumors derived from parental dsRed SKOV-3 cells, PGRMC1-deplete tumors: 1) developed in fewer mice, 2) formed less frequently, 3) appeared smaller, and 4) resulted in fewer oxyphilic clear cell tumors. These PGRMC1-deplete tumors were not responsive to CDDP's apoptotic effects. The failure to respond to CDDP could be due to their poorly developed microvasculature system as judged by percentage of CD31-stained endothelial cells and/or their increased expression of ATP-binding cassette transporters, which are involved in drug resistance. Taken together, these findings indicate that PGRMC1 plays an essential role in the development and CDDP sensitivity of human ovarian tumors.

Effects of oral contraceptives or a gonadotropin-releasing hormone agonist on ovarian carcinogenesis in genetically engineered mice

Although epidemiologic evidence for the ability of combined oral contraception (OC) to reduce the risk of ovarian cancer (OvCa) is convincing, the biological mechanisms underlying this effect are largely unknown. We conducted the present study to determine if OC also influences ovarian carcinogenesis in a genetic mouse model and, if so, to investigate the mechanism underlying the protective effect. LSL-K-ras(G12D/+)Pten(loxP/loxP) mice were treated with ethinyl estradiol plus norethindrone, contraceptive hormones commonly used in combined OC, or norethindrone alone, or a gonadotropin-releasing hormone agonist. The combined OC had a 29% reduction in mean total tumor weight compared with placebo (epithelial tumor weight, -80%). Norethindrone alone reduced mean total tumor weight by 42% (epithelial tumor weight, -46%), and the gonadotropin-releasing hormone agonist increased mean total tumor weight by 71% (epithelial tumor weight, +150%). Large variations in tumor size affected the P values for these changes, which were not statistically significant. Nonetheless, the OC reductions are consistent with the epidemiologic data indicating a protective effect of OC. Matrix metalloproteinase-2 activity was decreased in association with OC, indicating that OC may affect ovarian carcinogenesis by decreasing proteolytic activity, an important early event in the pathogenesis of OvCa. In contrast, OC increased invasion in a K-ras/Pten OvCa cell line established from the mouse tumors, suggesting that OC hormones, particularly estrogen, may have a detrimental effect after the disease process is under way. Our study results support further investigation of OC effects and mechanisms for OvCa prevention.

Estrous cycle modulates ovarian carcinoma growth

PURPOSE

The effects of reproductive hormones on ovarian cancer growth are not well understood. Here, we examined the effects of estrous cycle variation and specific reproductive hormones on ovarian cancer growth.

EXPERIMENTAL DESIGN

We investigated the role of reproductive hormones in ovarian cancer growth using both in vivo and in vitro models of tumor growth.

RESULTS

In vivo experiments using the HeyA8 and SKOV3ip1 ovarian cancer models showed that tumor cell inoculation during proestrus significantly increased tumor burden (251-273%) compared with injection during the estrus phase. Treatment of ovariectomized mice with 17beta-estradiol resulted in a 404% to 483% increase in tumor growth compared with controls. Progestins had no significant effect, but did block estrogen-stimulated tumor growth. Tumors collected from mice sacrificed during proestrus showed increased levels of vascular endothelial growth factor (VEGF) and microvessel density compared with mice injected during estrus. HeyA8, SKOV3ip1, and mouse endothelial (MOEC) cells expressed estrogen receptor alpha and beta and progesterone receptor at the protein and mRNA levels, whereas 2774 ovarian cancer cells were estrogen receptor-negative. In vitro assays showed that 17beta-estradiol significantly increased ovarian cancer cell adhesion to collagen in estrogen receptor-positive, but not in estrogen receptor-negative cells. Additionally, 17beta-estradiol increased the migratory potential of MOEC cells, which was abrogated by the mitogen-activated protein kinase (MAPK) inhibitor, PD 09859. Treatment with 17beta-estradiol activated MAPK in MOEC cells, but not in HeyA8 or SKOV3ip1 cells.

CONCLUSION

Our data suggest that estrogen may promote in vivo ovarian cancer growth, both directly and indirectly, by making the tumor microenvironment more conducive for cancer growth.

Progesterone facilitates cisplatin toxicity in epithelial ovarian cancer cells and xenografts

OBJECTIVES

The underlying premise of these investigations was that the lipophilic hormone progesterone, which partitions into and (at relatively high concentrations) impedes the fluid mechanics of the plasmalemma, would perturb integral associations between membrane lipids and exporter pumps that otherwise confer drug resistance. That progesterone can affect susceptibility of ovarian adenocarcinoma cells and xenografts to cisplatin was tested.

METHODS

The cisplatin-resistant human cell lines SKOV-3 and OVCAR-3 were treated for 24 hours with cisplatin (0.1 microg/ml)+/-progesterone (0.01, 0.1 microg/ml). Cytotoxicity and platinum were measured by MTT assay and inductively coupled plasma mass spectrometry, respectively. Athymic mice were inoculated intraperitoneal (ip) with SKOV-3 cells. Cisplatin (2 mg/kg/week)+/-progesterone (25 mg sustained-release pellet) regimens were initiated ip at one week (when micrometastases were present) and continued to six weeks post-xenograft. Tumor burdens, histopathology, and platinum concentrations were assessed upon necropsy at 24 hours after the final injection of cisplatin.

RESULTS

There were no significant in vitro/vivo anticancer effects of cisplatin alone. High-dose progesterone enhanced platinum accretion and induced drug toxicity in both cell lines. Tumorigenesis was suppressed by cisplatin+progesterone. The treatment synergy was related to elevated tumor platinum and morphological evidence of apoptosis.

CONCLUSION

It appears that the addition of progesterone to ovarian cancer therapeutic modalities represents a step in improving responses.

Regulation of ovarian cancer cell viability and sensitivity to cisplatin by progesterone receptor membrane component-1

CONTEXT

Progesterone (P4) influences ovarian cancer cells by an unknown mechanism.

OBJECTIVE

The objective was to determine whether P4 acts through progesterone receptor membrane component-1 (PGRMC1) in ovarian cancers.

DESIGN, SETTING AND PATIENTS

Archival tissue and cDNA provided by OriGene were used for expression studies. In vitro experiments were conducted with Ovcar-3 cells.

MAIN OUTCOME MEASURES

PCR, Western blot, and immunohistochemistry were used to measure expression of PGRMC1 and nuclear progesterone receptor (PGR). PGRMC1's role in regulating the viability of ovarian cancers was assessed by overexpressing PGRMC1, depleting PGRMC1 using small interfering RNA, and attenuating PGRMC1's action with a blocking antibody. Apoptosis was determined by 4',6'-diamino-2-phenylindole staining.

RESULTS

PGRMC1 mRNA increased and PGR mRNA decreased in advanced stages of ovarian cancer. Unlike PGR, PGRMC1 was expressed in virtually every cancer cell within the tumor. A similar relationship between PGRMC1 and PGR was observed in Ovcar-3 cells. In these cells P4 suppressed apoptosis induced by either serum withdrawal or cisplatin (CDDP). Moreover, in the presence of P4, the following occurs: 1) overexpression of PGRMC1 reduces the effectiveness of CDDP, 2) depletion of PGRMC1 with small interfering RNA enhances the effects of CDDP, and 3) PGRMC1 antibody treatment increases the apoptotic response to CDDP.

CONCLUSIONS

These findings indicate that PGRMC1 plays an important role in promoting ovarian cancer cell viability and that attenuating PGRMC1's action makes the ovarian cancer cells more sensitive to CDDP. These data suggest that targeted depletion of PGRMC1 could be useful as an adjunct to CDDP therapy.

Coordinate up-regulation of TMEM97 and cholesterol biosynthesis genes in normal ovarian surface epithelial cells treated with progesterone: implications for pathogenesis of ovarian cancer

Background

Ovarian cancer (OvCa) most often derives from ovarian surface epithelial (OSE) cells. Several lines of evidence strongly suggest that increased exposure to progesterone (P4) protects women against developing OvCa. However, the underlying mechanisms of this protection are incompletely understood.

Methods

To determine downstream gene targets of P4, we established short term in vitro cultures of non-neoplastic OSE cells from six subjects, exposed the cells to P4 (10^-6 M) for five days and performed transcriptional profiling with oligonucleotide microarrays containing over 22,000 transcripts.

Results

We identified concordant but modest gene expression changes in cholesterol/lipid homeostasis genes in three of six samples (responders), whereas the other three samples (non-responders) showed no expressional response to P4. The most up-regulated gene was TMEM97 which encodes a transmembrane protein of unknown function (MAC30). Analyses of outlier transcripts, whose expression levels changed most significantly upon P4 exposure, uncovered coordinate up-regulation of 14 cholesterol biosynthesis enzymes, insulin-induced gene 1, low density lipoprotein receptor, ABCG1, endothelial lipase, stearoyl- CoA and fatty acid desaturases, long-chain fatty-acyl elongase, and down-regulation of steroidogenic acute regulatory protein and ABCC6. Highly correlated tissue-specific expression patterns of TMEM97 and the cholesterol biosynthesis genes were confirmed by analysis of the GNF Atlas 2 universal gene expression database. Real-time quantitative RT-PCR analyses revealed 2.4-fold suppression of the TMEM97 gene expression in short-term cultures of OvCa relative to the normal OSE cells.

Conclusion

These findings suggest that a co-regulated transcript network of cholesterol/lipid homeostasis genes and TMEM97 are downstream targets of P4 in normal OSE cells and that TMEM97 plays a role in cholesterol and lipid metabolism. The P4-induced alterations in cholesterol and lipid metabolism in OSE cells might play a role in conferring protection against OvCa.

Endocrine signaling in ovarian surface epithelium and cancer

Ovarian cancer is the sixth most common cancer and the fifth leading cause of cancer-related death among women in developed countries. Greater than 85% of human ovarian cancer arises within the ovarian surface epithelium (OSE), with the remainder derived from granulosa cells or, rarely, stroma or germ cells. The pathophysiology of ovarian cancer is the least understood among all major human malignancies because of a poor understanding of the aetiological factors and mechanisms of ovarian cancer progression. There is increasing evidence suggesting that several key reproductive hormones, such as GnRH, gonadotrophins and sex steroids, regulate the growth of normal OSE and ovarian cancer cells. The objective of this review was to highlight the effects of these endocrine factors on ovarian cancer cell growth and to summarize the signalling mechanisms involved in normal human OSE and its neoplastic counterparts.