An estrogen receptor alpha-dependent regulation of estrogen receptor-related receptor alpha in the proliferation of endometrial carcinoma cells

Role of Estrogen Receptor β, G-Protein Coupled Estrogen Receptor and Estrogen-Related Receptors in Endometrial and Ovarian Cancer

Ovarian and endometrial cancers are affected by estrogens and their receptors. It has been long known that in different types of cancers, estrogens activate tumor cell proliferation via estrogen receptor α (ERα). In contrast, the role of ERs discovered later, including ERβ and G-protein-coupled ER (GPER1), in cancer is less well understood, but the current state of knowledge indicates them to have a considerable impact on both cancer development and progression. Moreover, estrogen related receptors (ERRs) have been reported to affect pathobiology of many tumor types. This article provides a summary and update of the current findings on the role of ERβ, GPER1, and ERRs in ovarian and endometrial cancer. For this purpose, original research articles on the role of ERβ, GPER1, and ERRs in ovarian and endometrial cancers listed in the PubMed database have been reviewed.

Dual targeting of estrogen receptor α and estrogen-related receptor α: a novel endocrine therapy for endometrial cancer

Background

Endometrial cancer (EC) is a hormone dependent carcinoma that may involve complex molecular mechanisms. Endocrine therapy by blocking the estrogen and estrogen receptor α (ERα) has been effective in breast cancer, while it is still controversial in EC. Recently, estrogen-related receptor α (ERRα) was proven to be another endocrine therapy target.

Methods

The anti-tumor effect of selective estrogen receptor modulators (SERMs) and XCT790 (XCT) used alone or in combination were evaluated in both of ERα-positive (ERα+) and ERα-negative (ERα-) EC cells. ERα and ERRα mRNA were tested by qPCR, while the protein was detected by Western blot. The proliferation was tested by MTS and cell cycle, apoptosis rate were analyzed by flow cytometry.

Results

A relatively high dose (10 μM) of tamoxifen (TAM) suppressed the expression of ERα and ERRα in two types of EC cells. However, 10 μM raloxifene (RAL) exhibited no effect on ERα and ERRα, while 10 μM XCT down regulated ERRα specifically, but not ERα in all EC cells. When dual targeting on ERα and ERRα by combining TAM with XCT, the proliferation inhibitory effect and apoptosis reached the strongest in all EC cells (P<0.05). Moreover, the inhibitory effect of proliferation was attributed significantly to the G0/G1 arrest (P<0.05). Interestingly, the apoptosis induced by combining TAM with XCT were obviously higher in ERα+ EC cells than ERα- EC cells (P<0.05).

Conclusion

Taken together, the results indicate that dual targeting on ERα and ERRα represents a better anti-tumor effect, which provides a novel endocrine based therapy strategy for EC.

miR-142 Suppresses Endometrial Cancer Proliferation In Vitro and In Vivo by Targeting Cyclin D1

Endometrial cancer (EC), a prevalent gynecologic tumor, is a great threat to women. We aimed to explore miR-142's effects on EC and the relevant mechanisms. Cell proliferation was evaluated with MTT, cell counting, and colony formation assay. MRNA abundances of miR-142 and cyclin D1 (CCND1) were examined with quantitative real-time PCR. CCND1 protein level in cells was analyzed with Western blot. miR-142's downstream target was identified with targetscan and luciferase reporter assay. Nude mice were injected subcutaneously with Ishikawa (ISK) cells transfected with or without miR-142 mimics. Ki-67 and CCND1 expressions in tumors of xenograft mice were analyzed with immunohistochemical assay. miR-142 was expressed at a lower level in human EC tumor samples than matched normal tissues, and its mRNA level in EC patients without metastasis was higher than that in patients with metastatic EC. Additionally, low-level miR-142 was closely linked with the poor prognosis of EC patients. miR-142 restricted ISK and HEC-1A cell proliferation. Targetscan and luciferase reporter assay proved the target relationship between miR-142 and CCND1. Moreover, high-level CCND1 was positively correlated with the poor prognosis of EC patients. Besides, miR-142 mimics restricted tumor growth in ISK xenografted mice, as well as inhibited the expression of Ki67 and CCND1 in excised tumors. miR-142 restricted EC proliferation by targeting CCND1.

Potential role of the HOXD8 transcription factor in cisplatin resistance and tumour metastasis in advanced epithelial ovarian cancer

Few studies have examined the potential transcription factor (TF) simultaneously associated with cisplatin resistance and metastasis in ovarian cancer. To assess a related mechanism, a 345-channel protein/DNA array and transcriptional activity ELISA were performed to compare the TF activities in the cisplatin-sensitive SKOV3 and cisplatin-resistant SKOV3-DDP cells and in HO-8910 and the homologous highly metastatic HO-8910PM cells. In SKOV3-DDP vs. SKOV3 cells, 43 TFs were up-regulated, while 31 were down-regulated. In HO-8910PM vs. HO-8910 cells, 13 TFs were up-regulated, while 18 were down-regulated. In these two models, 4 TFs (HOXD8(1), HOXD8(2), RB, RFX1/2/3) were simultaneously up-regulated, and 9 TFs (SRE, FKHR, Angiotensinogen ANG-IRE, Pax2, CD28RC/NF-IL2B, HLF, CPE, CBFB and c-Ets-1) were down-regulated. HOXD8 mRNA and protein expression levels measured by reverse transcription polymerase chain reaction and ELISA, respectively, were significantly higher in SKOV3-DDP and HO-8910PM than in their corresponding cell lines (both p < 0.05). In 52 cases of different ovarian disease, the patients with recurrent and cisplatin-resistant ovarian cancer had higher expression levels of HOXD8 than patients with primary malignant tumours (p = 0.018, p = 0.001) or benign tumours (p = 0.001, p < 0.001). Taken together, these results suggest that HOXD8 is potentially associated with both cisplatin resistance and metastasis in advanced ovarian cancer.

A suppressive role of guanine nucleotide-binding protein subunit beta-4 inhibited by DNA methylation in the growth of anti-estrogen resistant breast cancer cells

BACKGROUND

Breast cancer is the most common malignancy in women worldwide. Although the endocrine therapy that targets estrogen receptor α (ERα) signaling has been well established as an effective adjuvant treatment for patients with ERα-positive breast cancers, long-term exposure may eventually lead to the development of acquired resistance to the anti-estrogen drugs, such as fulvestrant and tamoxifen. A better understanding of the mechanisms underlying antiestrogen resistance and identification of the key molecules involved may help in overcoming antiestrogen resistance in breast cancer.

METHODS

The whole-genome gene expression and DNA methylation profilings were performed using fulvestrant-resistant cell line 182R-6 and tamoxifen-resistant cell line TAMR-1 as a model system. In addition, qRT-PCR and Western blot analysis were performed to determine the levels of mRNA and protein molecules. MTT, apoptosis and cell cycle analyses were performed to examine the effect of either guanine nucleotide-binding protein beta-4 (GNB4) overexpression or knockdown on cell proliferation, apoptosis and cell cycle.

RESULTS

Among 9 candidate genes, GNB4 was identified and validated by qRT-PCR as a potential target silenced by DNA methylation via DNA methyltransferase 3B (DNMT3B). We generated stable 182R-6 and TAMR-1 cell lines that are constantly expressing GNB4 and determined the effect of the ectopic GNB4 on cell proliferation, cell cycle, and apoptosis of the antiestrogen-resistant cells in response to either fulvestrant or tamoxifen. Ectopic expression of GNB4 in two antiestrogen resistant cell lines significantly promoted cell growth and shortened cell cycle in the presence of either fulvestrant or tamoxifen. The ectopic GNB4 induced apoptosis in 182R-6 cells, whereas it inhibited apoptosis in TAMR-1 cells. Many regulators controlling cell cycle and apoptosis were aberrantly expressed in two resistant cell lines in response to the enforced GNB4 expression, which may contribute to GNB4-mediated biologic and/or pathologic processes. Furthermore, knockdown of GNB4 decreased growth of both antiestrogen resistant and sensitive breast cancer cells.

CONCLUSION

GNB4 is important for growth of breast cancer cells and a potential target for treatment.

Novel endocrine therapeutic strategy in endometrial carcinoma targeting estrogen-related receptor α by XCT790 and siRNA

Purpose

To explore the targeted therapy of estrogen-related receptor α (ERRα) in endometrial cancer (EC) cells and its potential mechanisms.

Methods

The mRNA and protein expression levels of ERRα and estrogen receptor α (ERα) were detected by qPCR and Western blotting in RL-952, AN3-CA, HEC-1A, and HEC-1B EC cell lines. After treatment with the ERRα-specific antagonist XCT790 or infection with lentivirus-mediated small interfering RNA (siRNA) targeting the ERRα (siRNA-ERRα), cell proliferation and apoptosis were evaluated by MTS assay and flow cytometry. After treatment with siRNA-ERRα, the expression profiles of transcription factors (TFs) were analyzed by protein/DNA arrays in EC cells.

Results

The relative mRNA levels of ERRa in RL-952 (1±0.0831) and AN3-CA (1.162±0.0325) were significantly higher than those in HEC-1A (0.3081±0.0339) and HEC-1B (0.1119±0.0091) (P<0.05), and similar results were observed for ERRα protein levels. A higher ratio of ERa/ERRa was observed in ERα-positive RL-952 (10-fold) and ANC-3A (8.5-fold) cells, whereas a lower ratio was observed in ERα-negative HEC-1A (3.75-fold) and HEC-1B cells (0-fold). Both – exogenous XCT790 and endogenous siRNA-ERRα – can decrease the expression of ERRα, thereby inhibiting proliferation but promoting apoptosis in both ERα-positive and -negative EC cells. The XCT790 presented higher proliferation-inhibition and apoptosis rates in the ERα-positive than ERα-negative cells, whereas the siRNA-ERRα exhibited higher proliferation-inhibition and apoptosis rates in the ERα-negative than in ERα-positive cells. In total, 3 upregulated and 17 downregulated TFs were screened out by knocked-down expression of ERRα in all EC cells. Among them, the upregulated TFs organic cation transporter 3/4(Oct3/4), hepatic nuclear factor 4 (HNF4), HNF4 and chicken ovalbumin upstream TF (COUP-TF) as well as downregulated transcription factor EB (TFEB) were found to be statistically significant (P<0.05).

Conclusion

Targeting ERRα provides a promising novel endocrine therapeutic strategy.

Research progress on the reproductive and non-reproductive endocrine tumors by estrogen-related receptors

Oncologists have traditionally considered that tumorigenesis are closely related to classical nuclear estrogen receptors (ERs), such as estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), through the ligands binding and target gene transcription induction. Estrogen-related receptors (ERRs) have similar structures with ERs, which are also gradually thought to be relevant to reproductive endocrine tumor diseases, even non-reproductive endocrine tumors. In this review, different subtypes of ERRs and their structures firstly will be introduced, then the expression patterns in gynecological oncology (i.e., breast cancer, endometrial cancer, and ovarian cancer), male genitourinary system malignancy especially prostatic cancer along with other non-reproductive endocrine tumors (i.e., lung cancer, colorectal cancer, and liver cancer) will be described, and simultaneously the role of tumorigenesis related to ERRs will be discussed. Therefore, the review is benefit to explore the way of tumor prevention and treatment.

Insight into the mechanisms of action of estrogen receptor β in the breast, prostate, colon, and CNS

Estrogen and its receptors (ERs) influence many biological processes in physiology and pathology in men and women. ERs are involved in the etiology and/or progression of cancers of the prostate, breast, uterus, ovary, colon, lung, stomach, and malignancies of the immune system. In estrogen-sensitive malignancies, ERβ usually is a tumor suppressor and ERα is an oncogene. ERβ regulates genes in several key pathways including tumor suppression (p53, PTEN); metabolism (PI3K); survival (Akt); proliferation pathways (p45(Skp2), cMyc, and cyclin E); cell-cycle arresting factors (p21(WAF1), cyclin-dependent kinase inhibitor 1 (CDKN1A)), p27(Kip1), and cyclin-dependent kinases (CDKs); protection from reactive oxygen species, glutathione peroxidase. Because they are activated by small molecules, ERs are excellent targets for pharmaceuticals. ERα antagonists have been used for many years in the treatment of breast cancer and more recently pharmaceutical companies have produced agonists which are very selective for ERα or ERβ. ERβ agonists are being considered for preventing progression of cancer, treatment of anxiety and depression, as anti-inflammatory agents and as agents, which prevent or reduce the severity of neurodegenerative diseases.

Estrogen-related receptor ERRα-mediated downregulation of human hydroxysteroid sulfotransferase (SULT2A1) in Hep G2 cells

Hydroxysteroid sulfotransferase SULT2A1 catalyzes the sulfation of hydroxysteroids and xenobiotics. It plays an important role in the detoxification of hydroxyl-containing xenobiotics and in the regulation of the biological activities of hydroxysteroids. ERRα is an orphan member of the nuclear receptor superfamily that is closely related to estrogen receptor alpha (ERα). Here we report that the mRNA expression of human SULT2A1 was suppressed by ERRα in Hep G2 cells. To investigate the mechanisms of this regulation, the effects of ERRα on human SULT2A1 promoter transcription in Hep G2 cells were investigated. Reporter luciferase assay results showed that ERRα significantly represses human SULT2A1 promoter transcription in Hep G2 cells. Deletion analysis indicated that human SULT2A1 promoter region between positions -188 and -130 is necessary for its repression by ERRα in Hep G2 cells. The 5' DNA -188 to -130 region of human SULT2A1 contains IR2 and DR4 hormone response elements and two putative ERRα response elements (ERREs) (ERRE188: GCAAGCTCA and ERRE155: ATAAGTTCA). Interestingly, ERRE188 overlaps with the IR2 element and ERRE155 overlaps with the DR4 element. Our further investigation demonstrated that ERRα represses human SULT2A1 promoter transcription by competing with other nuclear receptors for binding to IR2 or DR4 elements. The interaction of ERRE188 and ERRE155 elements with ERRα was confirmed by electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) analysis. Our results suggest that ERRα may play an important role in regulating the metabolism of drugs and xenobiotics and in regulating endogenous hydroxysteroid activities via the regulation of SULT2A1.

Clinical characteristics of struma ovarii

OBJECTIVE

To evaluate the clinical characteristics of struma ovarii.

METHODS

Twenty-five cases of struma ovarii were reviewed retrospectively from June 1994 to April 2007. The presenting clinical, radiologic, and pathologic features of the patients were reviewed.

RESULTS

The mean age of the patients in this study was 45.3 years. The majority was of premenopausal status. Sixteen patients had clinical symptoms such as low abdominal pain, palpable abdominal mass and vaginal bleeding. Although one patient had an abnormal thyroid function test, the laboratory findings normalized after operative treatment. CA-125 levels were elevated in 6 cases. Diagnosis by preoperative imaging studies were 8 dermoid cysts, while only 3 cases were diagnosed as struma ovarii. There were 4 cases of malignant struma ovarii, and no patients with recurrent disease.

CONCLUSION

Struma ovarii is a rare tumor. The presented clinical, laboratory and radiological findings of patients are very diverse. The diagnosis was confirmed by pathologic findings. The treatment of benign struma ovarii is surgical resection only. The cases of malignant struma ovarii may need adjuvant treatment, but recurrence is uncommon.

The NR3B subgroup: an ovERRview

Members of the NR3B group of the nuclear receptor superfamily, known as the estrogen-related receptors (ERRs), were the first orphan receptors to be identified two decades ago. Despite the fact that a natural ligand has yet to be associated with the ERRs, considerable knowledge about their mode of action and biological functions has emerged through extensive biochemical, genetic and functional genomics studies. This review describes our current understanding of how the ERRs work as transcription factors and as such, how they control diverse developmental and physiological programs.