The chicken ovalbumin upstream promoter-transcription factor II negatively regulates the transactivation of androgen receptor in prostate cancer cells

International Union of Basic and Clinical Pharmacology CXIII: Nuclear Receptor Superfamily-Update 2023

The NR superfamily comprises 48 transcription factors in humans that control a plethora of gene network programs involved in a wide range of physiologic processes. This review will summarize and discuss recent progress in NR biology and drug development derived from integrating various approaches, including biophysical techniques, structural studies, and translational investigation. We also highlight how defective NR signaling results in various diseases and disorders and how NRs can be targeted for therapeutic intervention via modulation via binding to synthetic lipophilic ligands. Furthermore, we also review recent studies that improved our understanding of NR structure and signaling. SIGNIFICANCE STATEMENT: Nuclear receptors (NRs) are ligand-regulated transcription factors that are critical regulators of myriad physiological processes. NRs serve as receptors for an array of drugs, and in this review, we provide an update on recent research into the roles of these drug targets.

N/C Interactions Are Dispensable for Normal In Vivo Functioning of the Androgen Receptor in Male Mice

The androgen receptor (AR) plays a central role in the development and maintenance of the male phenotype. The binding of androgens to the receptor induces interactions between the carboxyterminal ligand-binding domain and the highly conserved 23FQNLF27 motif in the aminoterminal domain. The role of these so-called N/C interactions in AR functioning is debated. In vitro assays show that mutating the AR in the 23FQNLF27 motif (called ARNoC) attenuates the AR transactivation of reporter genes, has no effect on ligand binding, but does affect protein-protein interactions with several AR coregulators. To test the in vivo relevance of the N/C interaction, we analyzed the consequences of the genomic introduction of the ARNoC mutation in mice. Surprisingly, the ARNoC/Y mice show a normal male development, with unaffected male anogenital distance and normal accessory sex glands, male circulating androgen levels, body composition, and fertility. The responsiveness of androgen target genes in kidney, prostate, and testes was also unaffected. We thus conclude that the N/C interactions in the AR are not essential for the development of a male phenotype under normal physiological conditions.

Small-molecule inhibitor targeting orphan nuclear receptor COUP-TFII for prostate cancer treatment

The orphan nuclear receptor COUP-TFII is expressed at a low level in adult tissues, but its expression is increased and shown to promote progression of multiple diseases, including prostate cancer, heart failure, and muscular dystrophy. Suppression of COUP-TFII slows disease progression, making it an intriguing therapeutic target. Here, we identified a potent and specific COUP-TFII inhibitor through high-throughput screening. The inhibitor specifically suppressed COUP-TFII activity to regulate its target genes. Mechanistically, the inhibitor directly bound to the COUP-TFII ligand-binding domain and disrupted COUP-TFII interaction with transcription regulators, including FOXA1, thus repressing COUP-TFII activity on target gene regulation. Through blocking COUP-TFII's oncogenic activity in prostate cancer, the inhibitor efficiently exerted a potent antitumor effect in xenograft mouse models and patient-derived xenograft models. Our study identified a potent and specific COUP-TFII inhibitor that may be useful for the treatment of prostate cancer and possibly other diseases.

Recent progress on the role and molecular mechanism of chicken ovalbumin upstream promoter-transcription factor II in cancer

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) is an orphan receptor that regulates the expression of genes involved in development and homeostasis. COUP-TFII is also dysregulated in cancer, where it plays important roles in oncogenesis and malignant progression. Recent studies have also investigated altered microRNA-mediated regulation of COUP-TFII in cancer. Although many investigators have studied the expression and clinical significance of COUP-TFII in several cancer types, there remain many controversies regarding its role in these diseases. In this review, we will describe the functions and underlying molecular mechanisms of COUP-TFII in several cancers, especially colorectal, gastric, breast, and prostate cancer; additionally, we will briefly summarize what is known about microRNA-mediated regulation of COUP-TFII.

The nuclear receptor seven up functions in adipocytes and oenocytes to control distinct steps of Drosophila oogenesis

Reproduction is intimately linked to the physiology of an organism. Nuclear receptors are widely expressed transcription factors that mediate the effects of many circulating molecules on physiology and reproduction. While multiple studies have focused on the roles of nuclear receptors intrinsically in the ovary, it remains largely unknown how the actions of nuclear receptors in peripheral tissues influence oogenesis. We identified the nuclear receptor encoded by svp as a novel regulator of oogenesis in adult Drosophila. Global somatic knockdown of svp reduces egg production by increasing GSC loss, death of early germline cysts, and degeneration of vitellogenic follicles. Tissue-specific knockdown experiments revealed that svp remotely controls these different steps of oogenesis through separate mechanisms involving distinct tissues. Specifically, adipocyte-specific svp knockdown impairs GSC maintenance and early germline cyst survival, whereas oenocyte-specific svp knockdown increases the death of vitellogenic follicles without any effects on GSCs or early cysts. These results illustrate that nuclear receptors can control reproduction through a variety of mechanisms involving peripheral tissues.

The Role of Nuclear Receptors in Prostate Cancer

The nuclear receptor (NR) superfamily consists of 48 members that are divided into seven subfamilies. NRs are transcription factors that play an important role in a number of biological processes. The NR superfamily includes androgen receptor, which is a key player in prostate cancer pathogenesis, suggesting the functional roles of other NRs in prostate cancer. The findings on the roles of NRs in prostate cancer thus far have shown that several NRs such as vitamin D receptor, estrogen receptor β, and mineralocorticoid receptor play antioncogenic roles, while other NRs such as peroxisome proliferator-activated receptor γ and estrogen receptor α as well as androgen receptor play oncogenic roles. However, the roles of other NRs in prostate cancer remain controversial or uninvestigated. Further research on the role of NRs in prostate cancer is required and may lead to the development of novel preventions and therapeutics for prostate cancer.

The expression of p-mTOR and COUP-TFII correlates with increased lymphangiogenesis and lymph node metastasis in prostate adenocarcinoma

BACKGROUND

Mammalian target of rapamycin (mTOR) is a central regulator of major cellular processes such as growth and proliferation. Deregulated mTOR signaling is implicated in a wide spectrum of human malignancies including prostate cancer. The aim of this study is to address the role of phosphorylated mTOR (p-mTOR) in prostate adenocarcinoma-induced lymphangiogenesis and lymph node metastasis as well as to investigate its relationship with chicken ovalbumin upstream promoter transcriptional factor 2 (COUP-TFII) and the vascular endothelial growth factors A/C (VEGF A/C).

METHODS

We analyzed 92 paraffin embedded specimens from patients with prostate cancer who underwent radical prostatectomy with pelvic lymph node (LN) dissection. Twenty-four of these men were pathologically assessed to have regional LN metastasis (pN1 group) and 68 with negative lymph nodes (pN0 group). Lymph vessel density was measured using anti-D2-40 and anti-LYVE-1 antibodies. The expression of p-mTOR, COUP-TFII, and VEGF A/C was also evaluated by immunohistochemistry.

RESULTS

Specimens from pN1 group exhibited higher cytoplasmic p-mTOR expression compared to pN0 specimens. Mean vessel densities assessed by COUP-TFII and D2-40 were increased in pN1 tumors and positively associated with higher p-mTOR expression. Interestingly, increased expression of p-mTOR was positively associated with COUP-TFII expression in cancer cells and elevated immunoreactivity for both VEGF A and C, which in turn exhibited higher expression in pN1 group.

CONCLUSIONS

Our findings suggest that increased p-mTOR and COUP-TFII expression are implicated in human prostate adenocarcinoma-induced lymphangiogenesis and LN metastasis.

Nuclear receptor profiling in prostatospheroids and castration-resistant prostate cancer

Nuclear receptors (NRs), which belong to a superfamily of transcription factors and consist of a total of 48 members in humans, govern the expression of genes involved in a board range of developmental, reproductive, metabolic and immunological programs. Given the significant importance of androgen receptor and a few known NRs in the progression of prostate cancer, we surveyed the expression profiles of the entire NR superfamily in three-dimensional cultured prostatospheroids derived from different prostate cancer cell lines and a tumor xenograft model of castration-resistant prostate cancer VCaP-CRPC by quantitative real-time RT-PCR. Our results revealed that prostatospheroids and castration-relapse VCaP-CRPC xenografts, both contained enriched populations of prostate cancer stem/progenitor-like cells (PCSCs), displayed distinct expression patterns of NRs. Intriguingly, most of these differentially expressed NRs were orphan NRs and showed upregulation. Pairwise analysis identified five orphan NRs (including RORβ, TLX, COUP-TFII, NURR1 and LRH-1) that showed common upregulation in both mRNA and protein levels in the prostatospheroids and castration-relapse VCaP-CRPC xenografts, and overexpression of these orphan NRs could increase cancer stem cell marker expressions and enhance spheroid formation capacity in prostate cancer cells, suggesting that these orphan NRs might perform positive roles in the growth regulation of PCSCs and castration-resistant prostate cancer. Together, our NR expression dataset not only revealed the distinct physiologic status and regulatory roles governed by the networks of specific NRs but also some of these identified orphan NRs could be the potential therapeutic targets for PCSCs or castration-resistant prostate cancer.

MicroRNA-382 inhibits prostate cancer cell proliferation and metastasis through targeting COUP-TFII

MicroRNAs (miRNAs) have emerged as important regulators in cancer that are implicated in regulation of various cellular processes. miR-382 has been proposed as a tumor suppressor by several recent studies. However, the function of miR-382 in prostate cancer remains unknown. In this study, we aimed to investigate the potential function of miR-382 in prostate cancer. We found that miR-382 was significantly decreased in prostate cancer specimens and cancer cell lines. The overexpression of miR-382 in prostate cancer cells markedly inhibited cell proliferation, migration, and invasion. In contrast, miR-382 suppression exhibited an opposite effect. Target analysis predicted that chicken ovalbumin upstream promoter transcription factor II (COUP‑TFII) was a direct target of miR-382. This prediction was experimentally confirmed by dual-luciferase reporter assay, real-time quantitative polymerase chain reaction, and western blot analysis. Our results further demonstrated that miR-382 inhibited the downstream genes of COUP‑TFII, including Snail and matrix metalloproteinase 2 (MMP2). Moreover, the restoration of COUP‑TFII expression significantly blocked the inhibitory effect of miR-382 on cell proliferation, migration, and invasion, and Snail expression. Taken together, this study suggests that miR-382 inhibits prostate cancer cell proliferation and metastasis through inhibiting COUP‑TFII, representing an important new mechanism for understanding prostate cancer pathogenesis and providing a novel therapeutic candidate target for prostate cancer therapy.

The emerging roles of orphan nuclear receptors in prostate cancer

Orphan nuclear receptors are members of the nuclear receptor (NR) superfamily and are so named because their endogenous physiological ligands are either unknown or may not exist. Because of their important regulatory roles in many key physiological processes, dysregulation of signalings controlled by these receptors is associated with many diseases including cancer. Over years, studies of orphan NRs have become an area of great interest because their specific physiological and pathological roles have not been well-defined, and some of them are promising drug targets for diseases. The recently identified synthetic small molecule ligands, acting as agonists or antagonists, to these orphan NRs not only help to understand better their functional roles but also highlight that the signalings mediated by these ligand-independent NRs in diseases could be therapeutically intervened. This review is a summary of the recent advances in elucidating the emerging functional roles of orphan NRs in cancers, especially prostate cancer. In particular, some orphan NRs, RORγ, TR2, TR4, COUP-IFII, ERRα, DAX1 and SHP, exhibit crosstalk or interference with androgen receptor (AR) signaling in either normal or malignant prostatic cells, highlighting their involvement in prostate cancer progression as androgen and AR signaling pathway play critical roles in this process. We also propose that a better understanding of the mechanism of actions of these orphan NRs in prostate gland or prostate cancer could help to evaluate their potential value as therapeutic targets for prostate cancer.

Structures and regulation of non-X orphan nuclear receptors: A retinoid hypothesis

Nuclear receptors are defined as a family of ligand regulated transcription factors [1-6]. While this definition reflects that ligand binding is a key property of nuclear receptors, it is still a heated subject of debate if all the nuclear receptors (48 human members) can bind ligands (ligands referred here to both physiological and synthetic ligands). Recent studies in nuclear receptor structure biology and pharmacology have undoubtedly increased our knowledge of nuclear receptor functions and their regulation. As a result, they point to new avenues for the discovery and development of nuclear receptor regulators, including nuclear receptor ligands. Here we review the recent literature on orphan nuclear receptor structural analysis and ligand identification, particularly on the orphan nuclear receptors that do not heterodimerize with retinoid X receptors, which we term as non-X orphan receptors. We also propose a speculative "retinoid hypothesis" for a subset of non-X orphan nuclear receptors, which we hope to help shed light on orphan nuclear receptor biology and drug discovery. This article is part of a Special Issue entitled 'Orphan Nuclear Receptors'.

Network analysis of an in vitro model of androgen-resistance in prostate cancer

BACKGROUND

The development of androgen resistance is a major limitation to androgen deprivation treatment in prostate cancer. We have developed an in vitro model of androgen-resistance to characterise molecular changes occurring as androgen resistance evolves over time. Our aim is to understand biological network profiles of transcriptomic changes occurring during the transition to androgen-resistance and to validate these changes between our in vitro model and clinical datasets (paired samples before and after androgen-deprivation therapy of patients with advanced prostate cancer).

METHODS

We established an androgen-independent subline from LNCaP cells by prolonged exposure to androgen-deprivation. We examined phenotypic profiles and performed RNA-sequencing. The reads generated were compared to human clinical samples and were analysed using differential expression, pathway analysis and protein-protein interaction networks.

RESULTS

After 24 weeks of androgen-deprivation, LNCaP cells had increased proliferative and invasive behaviour compared to parental LNCaP, and its growth was no longer responsive to androgen. We identified key genes and pathways that overlap between our cell line and clinical RNA sequencing datasets and analysed the overlapping protein-protein interaction network that shared the same pattern of behaviour in both datasets. Mechanisms bypassing androgen receptor signalling pathways are significantly enriched. Several steroid hormone receptors are differentially expressed in both datasets. In particular, the progesterone receptor is significantly differentially expressed and is part of the interaction network disrupted in both datasets. Other signalling pathways commonly altered in prostate cancer, MAPK and PI3K-Akt pathways, are significantly enriched in both datasets.

CONCLUSIONS

The overlap between the human and cell-line differential expression profiles and protein networks was statistically significant showing that the cell-line model reproduces molecular patterns observed in clinical castrate resistant prostate cancer samples, making this cell line a useful tool in understanding castrate resistant prostate cancer. Pathway analysis revealed similar patterns of enriched pathways from differentially expressed genes of both human clinical and cell line datasets. Our analysis revealed several potential mechanisms and network interactions, including cooperative behaviours of other nuclear receptors, in particular the subfamily of steroid hormone receptors such as PGR and alteration to gene expression in both the MAPK and PI3K-Akt signalling pathways.

Orphan nuclear receptors as drug targets for the treatment of prostate and breast cancers

Nuclear receptors (NRs), a family of 48 transcriptional factors, have been studied intensively for their roles in cancer development and progression. The presence of distinctive ligand binding sites capable of interacting with small molecules has made NRs attractive targets for developing cancer therapeutics. In particular, a number of drugs have been developed over the years to target human androgen- and estrogen receptors for the treatment of prostate cancer and breast cancer. In contrast, orphan nuclear receptors (ONRs), which in many cases lack known biological functions or ligands, are still largely under investigated. This review is a summary on ONRs that have been implicated in prostate and breast cancers, specifically retinoic acid-receptor-related orphan receptors (RORs), liver X receptors (LXRs), chicken ovalbumin upstream promoter transcription factors (COUP-TFs), estrogen related receptors (ERRs), nerve growth factor 1B-like receptors, and ‘‘dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1’’ (DAX1). Discovery and development of small molecules that can bind at various functional sites on these ONRs will help determine their biological functions. In addition, these molecules have the potential to act as prototypes for future drug development. Ultimately, the therapeutic value of targeting the ONRs may go well beyond prostate and breast cancers.

The critical roles of COUP-TFII in tumor progression and metastasis

Chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) belongs to the steroid/thyroid hormone receptor superfamily. Extensive evidence has indicated that COUP-TFII plays a critical and indispensable role in cell-fate specification, organogenesis, angiogenesis, and metabolism as well as in a variety of diseases. Recent studies obtained from genetically engineered mouse models (GEM) and patient specimen analysis indicate that COUP-TFII is also important for tumor progression and metastasis. In this article, we will comprehensively review the oncogenic roles of COUP-TFII within the tumor microenvironment and tumor cells and delineate the mechanism by which COUP-TFII contributes to tumorigenesis. The applicability of current data to our understanding of the role of COUP-TFII in cancer and the potential therapeutic implications will also be discussed.

COUP-TFII regulates metastasis of colorectal adenocarcinoma cells by modulating Snail1

BACKGROUND

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII, also known as NR2F2) promotes metastasis by functioning in the tumour microenvironment; however, the role of COUP-TFII in colorectal cancer remains unknown.

METHODS

Human colon adenocarcinoma tissues were collected to test COUP-TFII expression. Wound-healing and cell invasion assay were used to evaluate migration and invasion of cells. Chicken ovalbumin upstream promoter-transcription factor II and related protein expression was assessed by immunostaining, immunoblotting and real-time PCR assay. Tamoxifen-inducible COUP-TFII knockout mice were employed to test COUP-TFII functions on colon cancer metastasis in vivo.

RESULTS

Elevated expression of COUP-TFII in colorectal adenocarcinoma tissue correlated with overexpression of the Snail1 transcription factor. High COUP-TFII expression correlated with metastasis and shorter patient survival. Chicken ovalbumin upstream promoter-transcription factor II regulated the migration and invasion of cancer cells. With Snail1, COUP-TFII inhibited expression of adherence molecules such as ZO-1, E-cadherin and β-catenin in colorectal cancer cells. Overexpression of COUP-TFII was required for cancer cells to metastasise in vivo. Chicken ovalbumin upstream promoter-transcription factor II regulated the transcription and expression of Snail1 by directly targeting the Snail1 promoter and regulated associated genes.

CONCLUSIONS

Chicken ovalbumin upstream promoter-transcription factor II was crucial for colorectal cancer metastasis and regulated cell migration and metastasis in conjunction with Snail1. Chicken ovalbumin upstream promoter-transcription factor II was found to be a biomarker associated with patient survival and colorectal cancer metastasis.

COUP-TFII inhibits NFkappaB activation in endocrine-resistant breast cancer cells

Reduced COUP-TFII expression contributes to endocrine resistance in breast cancer cells. Endocrine-resistant breast cancer cells have higher NFkappa B (NFκB) activity and target gene expression. The goal of this study was to determine if COUP-TFII modulates NFκB activity. Endocrine-resistant LCC9 cells with low endogenous COUP-TFII displayed ∼5-fold higher basal NFκB activity than parental endocrine-sensitive MCF-7 breast cancer cells. Transient transfection of LCC9 cells with COUP-TFII inhibited NFκB activation and reduced NFκB target gene expression. COUP-TFII and NFκB were inversely correlated in breast cancer patient samples. Endogenous COUP-TFII coimmunoprecipitated with NFκB subunits RelB and NFκB1 in MCF-7 cells. COUP-TFII inhibited NFκB-DNA binding in vitro and impaired coactivator induced NFκB transactivation. LCC9 cells were growth-inhibited by an NFκB inhibitor and 4-hydroxytamoxifen compared to MCF-7 cells. Together these data indicate a novel role for COUP-TFII in suppression of NFκB activity and explain, in part, why decreased COUP-TFII expression results in an endocrine-resistant phenotype.

Minireview: role of orphan nuclear receptors in cancer and potential as drug targets

The nuclear orphan receptors for which endogenous ligands have not been identified include nuclear receptor (NR)0B1 (adrenal hypoplasia congenita critical region on chromosome X gene), NR0B2 (small heterodimer partner), NR1D1/2 (Rev-Erbα/β), NR2C1 (testicular receptor 2), NR2C2 (testicular receptor 4), NR2E1 (tailless), NR2E3 (photoreceptor-specific NR [PNR]), NR2F1 chicken ovalbumin upstream promoter transcription factor 1 (COUP-TFI), NR2F2 (COUP-TFII), NR2F6 (v-erbA-related protein), NR4A1 (Nur77), NR4A2 (Nurr1), NR4A3 (Nor1), and NR6A1 (GCNF). These receptors play essential roles in development, cellular homeostasis, and disease including cancer where over- or underexpression of some receptors has prognostic significance for patient survival. Results of receptor knockdown or overexpression in vivo and in cancer cell lines demonstrate that orphan receptors exhibit tumor-specific pro-oncogenic or tumor suppressor-like activity. For example, COUP-TFII expression is both a positive (ovarian) and negative (prostate and breast) prognostic factor for cancer patients; in contrast, the prognostic activity of adrenal hypoplasia congenita critical region on chromosome X gene for the same tumors is the inverse of COUP-TFII. Functional studies show that Nur77 is tumor suppressor like in acute leukemia, whereas silencing Nur77 in pancreatic, colon, lung, lymphoma, melanoma, cervical, ovarian, gastric, and some breast cancer cell lines induces one or more of several responses including growth inhibition and decreased survival, migration, and invasion. Although endogenous ligands for the orphan receptors have not been identified, there is increasing evidence that different structural classes of compounds activate, inactivate, and directly bind several orphan receptors. Thus, the screening and development of selective orphan receptor modulators will have important clinical applications as novel mechanism-based agents for treating cancer patients overexpressing one or more orphan receptors and also for combined drug therapies.

The orphan nuclear receptors in cancer and diabetes

The orphan nuclear receptors (ONRs) are a vital class of transcriptional regulators belonging to the larger nuclear receptors (NRs) superfamily in higher eukaryotes. As a result of non-identification of endogenous physiological ligands for this class of NRs, they are designated as "orphans". The ONRs on receiving appropriate signals translate into specific gene regulation. Elaborate studies on the ONRs in the past two decades have revealed crucial biological functions controlled by them relating to general metabolism, immunity, organogenesis, angiogenesis, growth and development, and numerous other tissue physiologies. Over the years, many of the ONRs have been studied for their participatory role in human health and disease. Results obtained are encouraging and interesting and shows a number of ONRs does modulate several patho-physiological conditions such as cancer and diabetes. This review discusses the current status about the interplay between select ONRs in cancer and diabetes.