Mechanisms of androgen receptor signalling via steroid receptor coactivator-1 in prostate

N-terminal domain of androgen receptor is a major therapeutic barrier and potential pharmacological target for treating castration resistant prostate cancer: a comprehensive review

The incidence rate of prostate cancer (PCa) has risen by 3% per year from 2014 through 2019 in the United States. An estimated 34,700 people will die from PCa in 2023, corresponding to 95 deaths per day. Castration resistant prostate cancer (CRPC) is the leading cause of deaths among men with PCa. Androgen receptor (AR) plays a critical role in the development of CRPC. N-terminal domain (NTD) is the essential functional domain for AR transcriptional activation, in which modular activation function-1 (AF-1) is important for gene regulation and protein interactions. Over last 2 decades drug discovery against NTD has attracted interest for CRPC treatment. However, NTD is an intrinsically disordered domain without stable three-dimensional structure, which has so far hampered the development of drugs targeting this highly dynamic structure. Employing high throughput cell-based assays, small-molecule NTD inhibitors exhibit a variety of unexpected properties, ranging from specific binding to NTD, blocking AR transactivation, and suppressing oncogenic proliferation, which prompts its evaluation in clinical trials. Furthermore, molecular dynamics simulations reveal that compounds can induce the formation of collapsed helical states. Nevertheless, our knowledge of NTD structure has been limited to the primary sequence of amino acid chain and a few secondary structure motif, acting as a barrier for computational and pharmaceutical analysis to decipher dynamic conformation and drug-target interaction. In this review, we provide an overview on the sequence-structure-function relationships of NTD, including the polymorphism of mono-amino acid repeats, functional elements for transcription regulation, and modeled tertiary structure of NTD. Moreover, we summarize the activities and therapeutic potential of current NTD-targeting inhibitors and outline different experimental methods contributing to screening novel compounds. Finally, we discuss current directions for structure-based drug design and potential breakthroughs for exploring pharmacological motifs and pockets in NTD, which could contribute to the discovery of new NTD inhibitors.

Discovery of a peptide proteolysis-targeting chimera (PROTAC) drug of p300 for prostate cancer therapy

BACKGROUND

The E1A-associated protein p300 (p300) has emerged as a promising target for cancer therapy due to its crucial role in promoting oncogenic signaling pathways in various cancers, including prostate cancer. This need is particularly significant in prostate cancer. While androgen deprivation therapy (ADT) has demonstrated promising efficacy in prostate cancer, its long-term use can eventually lead to the development of castration-resistant prostate cancer (CRPC) and neuroendocrine prostate cancer (NEPC). Notably, p300 has been identified as an important co-activator of the androgen receptor (AR), highlighting its significance in prostate cancer progression. Moreover, recent studies have revealed the involvement of p300 in AR-independent oncogenes associated with NEPC. Therefore, the blockade of p300 may emerge as an effective therapeutic strategy to address the challenges posed by both CRPC and NEPC.

METHODS

We employed AI-assisted design to develop a peptide-based PROTAC (proteolysis-targeting chimera) drug that targets p300, effectively degrading p300 in vitro and in vivo utilizing nano-selenium as a peptide drug delivery system.

FINDINGS

Our p300-targeting peptide PROTAC drug demonstrated effective p300 degradation and cancer cell-killing capabilities in both CRPC, AR-negative, and NEPC cells. This study demonstrated the efficacy of a p300-targeting drug in NEPC cells. In both AR-positive and AR-negative mouse models, the p300 PROTAC drug showed potent p300 degradation and tumor suppression.

INTERPRETATION

The design of peptide PROTAC drug targeting p300 is feasible and represents an efficient therapeutic strategy for CRPC, AR-negative prostate cancer, and NEPC.

FUNDING

The funding details can be found in the Acknowledgements section.

Androgen receptor cofactors: A potential role in understanding prostate cancer

Prostate cancer (PCa) is witnessing a concerning rise in incidence annually, with the androgen receptor (AR) emerging as a pivotal contributor to its growth and progression. Mounting evidence underscores the AR's ability to recruit cofactors, influencing downstream gene transcription and thereby fueling the proliferation and metastasis of PCa cells. Although, clinical strategies involving AR antagonists provide some relief, managing castration resistant prostate cancer (CRPC) remains a formidable challenge. Thus, the need of the hour lies in unearthing new drugs or therapeutic targets to effectively combat PCa. This review encapsulates the pivotal roles played by coactivators and corepressors of AR, notably androgen receptor-associated protein (ARA) and steroid receptor Coactivators (SRC) in PCa. Our data unveils how these cofactors intricately modulate histone modifications, cell cycling, SUMOylation, and apoptosis through their interactions with AR. Among the array of cofactors scrutinised, such as ARA70β, ARA24, ARA160, ARA55, ARA54, PIAS1, PIAS3, SRC1, SRC2, SRC3, PCAF, p300/CBP, MED1, and CARM1, several exhibit upregulation in PCa. Conversely, other cofactors like ARA70α, PIASy, and NCoR/SMRT demonstrate downregulation. This duality underscores the complexity of AR cofactor dynamics in PCa. Based on our findings, we propose that manipulating cofactor regulation to modulate AR function holds promise as a novel therapeutic avenue against advanced PCa. This paradigm shift offers renewed hope in the quest for effective treatments in the face of CRPC's formidable challenges.

Evaluation of AR, AR-V7, and p160 family as biomarkers for prostate cancer: insights into the clinical significance and disease progression

PURPOSE

To assess the role of the p160 family, AR, and AR-V7 in different initial presentations of prostate cancer and their association with clinical endpoints related to tumor progression.

METHODS

The study sample comprises 155 patients who underwent radical prostatectomy and 11 healthy peripheral zone biopsies as the control group. Gene expression was quantified by qPCR from the tissue specimens. The statistical analysis investigated correlations between gene expression levels, associations with disease presence, and clinicopathological features. Additionally, ROC curves were applied for distinct PCa presentations, and time-to-event analysis was used for clinical endpoints.

RESULTS

The AR-V7 diagnostic performance for any PCa yielded an AUC of 0.77 (p < 0.05). For locally advanced PCa, the AR-V7 AUC was 0.65 (p < 0.05). Moreover, the metastasis group had a higher expression of SRC-1 than the non-metastatic group (p < 0.05), showing a shorter time to metastasis in the over-expressed group (p = 0.005). Patients with disease recurrence had super-expression of AR levels (p < 0.0005), with a shorter time-to-recurrence in the super-expression group (p < 0.0001).

CONCLUSION

Upregulation of SRC-1 indicates a higher risk of progression to metastatic disease in a shorter period, which warrants further research to be applied as a clinical tool. Additionally, AR may be used as a predictor for PCa recurrence. Furthermore, AR-V7 may be helpful as a diagnostic tool for PCa and locally advanced cancer, comparable with other investigated tools.

Effect of Kangfuxiaomi suppository on pelvic inflammatory disease in rats

Pelvic inflammatory disease (PID) is commonly encountered in gynecological practice. Kangfuxiaomi suppository, made from the compound extract of Periplaneta Americana, is a Traditional Chinese Medicine remedy widely used for the treatment of gynecological disorders. This study aimed to preliminarily explore the therapeutic effect of Kangfuxiaomi suppository in a rat model of PID established by chemical injury and pathogen infection. The key parameters assessed were vulvar inflammation score, vaginal + uterine organ index, and serum levels of interleukin (IL)- 8; tumor necrosis factor (TNF)-α; C-reactive protein (CRP); superoxide dismutase (SOD); and malondialdehyde (MDA). In addition, levels of IL-6, cyclooxygenase (COX)- 2, and IL-2 in cervical tissues as well as that of IL-1β and prostaglandin E-2 (PGE2) in uterine tissues were measured. The expression levels of nuclear factor-kappa B (NF-κB) p65 and Toll-like receptor 4 (TLR4) in uterine tissues were detected by immunohistochemical method. After Kangfuxiaomi suppository treatment, the vulva inflammation score and histopathological score of PID rats showed a tendency to decrease. Serum IL-8, TNF-α, CRP, and MDA levels were reduced, while SOD levels were significantly increased. Levels of IL-6, IL-2, and COX-2 in cervical tissues were somewhat decreased, and PGE2 and IL-1β levels in uterine tissue were significantly decreased. Moreover, the levels of NF-κB p65 and TLR4 protein expression were also decreased. These findings demonstrated the therapeutic effect of Kangfuxiaomi suppository in PID rats. The underlying mechanism may involve enhanced antioxidant capacity and decreased secretion of proinflammatory factors via the NF-κB/TLR4 signaling pathway.

Incidence of Prostate Cancer in Transgender Women Undergoing Androgen Deprivation Therapy: A Review

Transwomen frequently undergo androgen deprivation therapy (ADT) incorporated with oestrogen, but they are still prone to the occurrence of prostatic cancer since the prostate remains intact. The probability of this clinical condition reduces as compared with the general male population. This study aimed to study the occurrence of prostatic malignancy under hormonal therapy such as ADT in transwomen. An extensive literature search was performed using online searches on transgender health, centring on the incidence, diagnosis, treatment and management of prostate cancer in transgender women. Original articles from 1975 to 2022 were searched using PubMed, Scopus, EMBASE, DOAJ and Cochrane databases. Physical, mental and communal deliberation of health development is the major constituent of trans-health. It exhibits a fivefold reduction in prostatic malignancies in transwomen undergoing hormonal therapy contrasted with the extensive male community of indistinguishable age.

Castration-Resistant Prostate Cancer: From Uncovered Resistance Mechanisms to Current Treatments

Prostate cancer (PC) is the second most common cancer in men worldwide. Despite recent advances in diagnosis and treatment, castration-resistant prostate cancer (CRPC) remains a significant medical challenge. Prostate cancer cells can develop mechanisms to resist androgen deprivation therapy, such as AR overexpression, AR mutations, alterations in AR coregulators, increased steroidogenic signaling pathways, outlaw pathways, and bypass pathways. Various treatment options for CRPC exist, including androgen deprivation therapy, chemotherapy, immunotherapy, localized or systemic therapeutic radiation, and PARP inhibitors. However, more research is needed to combat CRPC effectively. Further investigation into the underlying mechanisms of the disease and the development of new therapeutic strategies will be crucial in improving patient outcomes. The present work summarizes the current knowledge regarding the underlying mechanisms that promote CRPC, including both AR-dependent and independent pathways. Additionally, we provide an overview of the currently approved therapeutic options for CRPC, with special emphasis on chemotherapy, radiation therapy, immunotherapy, PARP inhibitors, and potential combination strategies.

Artepillin C overcomes apalutamide resistance through blocking androgen signaling in prostate cancer cells

Prostate cancer has a relatively good prognosis, but most cases develop resistance to hormone therapy, leading to castration-resistant prostate cancer (CRPC). Androgen receptor (AR) antagonists and a cytochrome P450 17A1 inhibitor have been used to treat CRPC, but cancer cells readily develop resistance to these drugs. In this study, to improve the therapy of CRPC, we searched for natural compounds which block androgen signaling. Among cinnamic acid derivatives contained in Brazilian green propolis, artepillin C (ArtC) suppressed expressions of androgen-induced prostate-specific antigen and transmembrane protease serine 2 in a dose-dependent manner. Reporter assays revealed that ArtC displayed AR antagonist activity, albeit weaker than an AR antagonist flutamide. In general, aberrant activation of the androgen signaling is involved in the resistance of prostate cancer cells to hormone therapy. Recently, apalutamide, a novel AR antagonist, has been in clinical use, but its drug-resistant cases have been already reported. To search for compounds which overcome the resistance to apalutamide, we established apalutamide-resistant prostate cancer 22Rv1 cells (22Rv1/APA). The 22Rv1/APA cells showed higher AR expression and androgen sensitivity than parental 22Rv1 cells. ArtC inhibited androgen-induced proliferation of 22Rv1/APA cells by suppressing the enhanced androgen signaling through blocking the nuclear translocation of AR. In addition, ArtC potently sensitized the resistant cells to apalutamide by inducing apoptotic cell death due to mitochondrial dysfunction. These results suggest that the intake of Brazilian green propolis containing ArtC improves prostate cancer therapy.

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.

Cistrome and transcriptome analysis identifies unique androgen receptor (AR) and AR-V7 splice variant chromatin binding and transcriptional activities

The constitutively active androgen receptor (AR) splice variant, AR-V7, plays an important role in resistance to androgen deprivation therapy in castration resistant prostate cancer (CRPC). Studies seeking to determine whether AR-V7 is a partial mimic of the AR, or also has unique activities, and whether the AR-V7 cistrome contains unique binding sites have yielded conflicting results. One limitation in many studies has been the low level of AR variant compared to AR. Here, LNCaP and VCaP cell lines in which AR-V7 expression can be induced to match the level of AR, were used to compare the activities of AR and AR-V7. The two AR isoforms shared many targets, but overall had distinct transcriptomes. Optimal induction of novel targets sometimes required more receptor isoform than classical targets such as PSA. The isoforms displayed remarkably different cistromes with numerous differential binding sites. Some of the unique AR-V7 sites were located proximal to the transcription start sites (TSS). A de novo binding motif similar to a half ARE was identified in many AR-V7 preferential sites and, in contrast to conventional half ARE sites that bind AR-V7, FOXA1 was not enriched at these sites. This supports the concept that the AR isoforms have unique actions with the potential to serve as biomarkers or novel therapeutic targets.

Unravelling the Role of Kinases That Underpin Androgen Signalling in Prostate Cancer

The androgen receptor (AR) signalling pathway is the key driver in most prostate cancers (PCa), and is underpinned by several kinases both upstream and downstream of the AR. Many popular therapies for PCa that target the AR directly, however, have been circumvented by AR mutation, such as androgen receptor variants. Some upstream kinases promote AR signalling, including those which phosphorylate the AR and others that are AR-regulated, and androgen regulated kinase that can also form feed-forward activation circuits to promotes AR function. All of these kinases represent potentially druggable targets for PCa. There has generally been a divide in reviews reporting on pathways upstream of the AR and those reporting on AR-regulated genes despite the overlap that constitutes the promotion of AR signalling and PCa progression. In this review, we aim to elucidate which kinases—both upstream and AR-regulated—may be therapeutic targets and require future investigation and ongoing trials in developing kinase inhibitors for PCa.

Endocrine Disruptors and Prostate Cancer

The role of endocrine disruptors (EDs) in the human prostate gland is an overlooked issue even though the prostate is essential for male fertility. From experimental models, it is known that EDs can influence several molecular mechanisms involved in prostate homeostasis and diseases, including prostate cancer (PCa), one of the most common cancers in the male, whose onset and progression is characterized by the deregulation of several cellular pathways including androgen receptor (AR) signaling. The prostate gland essentiality relies on its function to produce and secrete the prostatic fluid, a component of the seminal fluid, needed to keep alive and functional sperms upon ejaculation. In physiological condition, in the prostate epithelium the more-active androgen, the 5α-dihydrotestosterone (DHT), formed from testosterone (T) by the 5α-reductase enzyme (SRD5A), binds to AR and, upon homodimerization and nuclear translocation, recognizes the promoter of target genes modulating them. In pathological conditions, AR mutations and/or less specific AR binding by ligands modulate differently targeted genes leading to an altered regulation of cell proliferation and triggering PCa onset and development. EDs acting on the AR-dependent signaling within the prostate gland can contribute to the PCa onset and to exacerbating its development.

Umbelliferone Ameliorates Benign Prostatic Hyperplasia by Inhibiting Cell Proliferation and G1/S Phase Cell Cycle Progression through Regulation of STAT3/E2F1 Axis

Umbelliferone (UMB), also known as 7-hydroxycoumarin, is a derivative of coumarin, which is widely found in many plants such as carrots, coriander, and garden angelica. Although many studies have already revealed the various pharmacological properties of UMB, its effect on benign prostatic hyperplasia (BPH) remains unclear. Therefore, the present study aimed to elucidate the underlying mechanism of the anti-proliferative effect of UMB in a human benign prostatic hyperplasia cell line (BPH-1), as well as its ameliorative effect on BPH in testosterone propionate (TP)-induced rats. The results showed that UMB exerts an anti-proliferative effect in BPH-1 cells by modulating the signal transducer and activator of transcription 3 (STAT3)/E2F transcription factor 1 (E2F1) axis. UMB treatment not only inhibited androgen/androgen receptor (AR) signaling-related markers, but also downregulated the overexpression of G1/S phase cell cycle-related markers. In TP-induced rats, UMB administration demonstrated an anti-BPH effect by significantly reducing prostate size, weight, and epithelial thickness. In addition, UMB suppressed cell proliferation by reducing the expression of proliferating cell nuclear antigen (PCNA) and p-STAT3 (Tyr 705) in prostate tissue following TP injection. These findings suggest that UMB has pharmacological effects against BPH.

CBP/p300: Critical Co-Activators for Nuclear Steroid Hormone Receptors and Emerging Therapeutic Targets in Prostate and Breast Cancers

The CREB-binding protein (CBP) and p300 are two paralogous lysine acetyltransferases (KATs) that were discovered in the 1980s-1990s. Since their discovery, CBP/p300 have emerged as important regulatory proteins due to their ability to acetylate histone and non-histone proteins to modulate transcription. Work in the last 20 years has firmly established CBP/p300 as critical regulators for nuclear hormone signaling pathways, which drive tumor growth in several cancer types. Indeed, CBP/p300 are critical co-activators for the androgen receptor (AR) and estrogen receptor (ER) signaling in prostate and breast cancer, respectively. The AR and ER are stimulated by sex hormones and function as transcription factors to regulate genes involved in cell cycle progression, metabolism, and other cellular functions that contribute to oncogenesis. Recent structural studies of the AR/p300 and ER/p300 complexes have provided critical insights into the mechanism by which p300 interacts with and activates AR- and ER-mediated transcription. Breast and prostate cancer rank the first and forth respectively in cancer diagnoses worldwide and effective treatments are urgently needed. Recent efforts have identified specific and potent CBP/p300 inhibitors that target the acetyltransferase activity and the acetytllysine-binding bromodomain (BD) of CBP/p300. These compounds inhibit AR signaling and tumor growth in prostate cancer. CBP/p300 inhibitors may also be applicable for treating breast and other hormone-dependent cancers. Here we provide an in-depth account of the critical roles of CBP/p300 in regulating the AR and ER signaling pathways and discuss the potential of CBP/p300 inhibitors for treating prostate and breast cancer.

Eighty Years of Targeting Androgen Receptor Activity in Prostate Cancer: The Fight Goes on

Simple Summary

Prostate cancer is the second most common cancer in men world-wide, with nearly 1.3 million new cases each year, and over the next twenty years the incidence and death rate are predicted to nearly double. For decades, this lethal disease has been more or less successfully treated using hormonal therapy, which has the ultimate aim of inhibiting androgen signalling. However, prostate tumours can evade such hormonal therapies in a number of different ways and therapy resistant disease, so-called castration-resistant prostate cancer (CRPC) is the major clinical problem. Somewhat counterintuitively, the androgen receptor remains a key therapy target in CRPC. Here, we explain why this is the case and summarise both new hormone therapy strategies and the recent advances in knowledge of androgen receptor structure and function that underpin them.

Abstract

Prostate cancer (PCa) is the most common cancer in men in the West, other than skin cancer, accounting for over a quarter of cancer diagnoses in US men. In a seminal paper from 1941, Huggins and Hodges demonstrated that prostate tumours and metastatic disease were sensitive to the presence or absence of androgenic hormones. The first hormonal therapy for PCa was thus castration. In the subsequent eighty years, targeting the androgen signalling axis, where possible using drugs rather than surgery, has been a mainstay in the treatment of advanced and metastatic disease. Androgens signal via the androgen receptor, a ligand-activated transcription factor, which is the direct target of many such drugs. In this review we discuss the role of the androgen receptor in PCa and how the combination of structural information and functional screenings is continuing to be used for the discovery of new drug to switch off the receptor or modify its function in cancer cells.

An androgen-independent mechanism underlying the androgenic effects of 3-methylcholanthrene, a potent aryl hydrocarbon receptor agonist

Aryl hydrocarbon receptor (AhR) and androgen receptor (AR) are ligand-activated transcription factors with profound cross-talk between their signal transduction pathways. Previous studies have shown that AhR agonists activate the transcription of AR-regulated genes in an androgen-independent manner; however, the underlying mechanism remains unclear. To decipher this mechanism, we evaluated the effects of 3-methylcholanthrene (3MC), a potent AhR agonist, on the transcription of AR-regulated genes in three AR-expressing cell lines. 3MC induced the expression of not only three representative AR-regulated chromosomal genes but also the exogenous AR-responsive luciferase reporter gene. No significant difference in the 3MC-induced luciferase activity was detected in the presence of SKF-525A, a non-specific inhibitor of CYP enzymes. The androgenic effects of 3MC were diminished by AhR and AR knockdown. Following 3MC treatment, the amount of nuclear AhR and AR increased synchronously. Co-immunoprecipitation revealed that AhR and AR formed a complex in the nucleus of cells treated with 3MC. AR was recruited to the proximal promoter and distal enhancer regions of the PSA gene upon the addition of 3MC. We propose that AhR activated by 3MC forms a complex with unliganded AR which translocates from the cytoplasm to the nucleus. Nuclear AR now binds the transcriptional regulatory region of AR-regulated genes and activates the transcription.

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.

Enhancement of androgen transcriptional activation assay based on genome edited glucocorticoid knock out human prostate cancer cell line

Endocrine-disrupting chemicals (EDCs) interfere with the biological activity of hormones. Among EDC's, (anti-)androgenic compounds potentially cause several androgen-related diseases. To improve the accuracy of an in vitro transactivation assay (TA) for detection of (anti-)androgenic compounds, We established the glucocorticoid receptor (GR) knockout 22Rv1/MMTV cell line by using an RNA-guided engineered nuclease (RGEN)-derived CRISPR/Cas system. The 22Rv1/MMTV GRKO cell line was characterized and validated by androgen receptor (AR)-mediated TA assay compared with the AR-TA assay using 22Rv1/MMTV. In conclusion, the AR-TA assay with the 22Rv1/MMTV GRKO cell line was more accurate, excluding the misleading signals derived from glucocorticoids or equivalent chemicals, and might be an effective method for screening potential (anti-)androgenic compounds.

Radiolabelled Aptamers for Theranostic Treatment of Cancer

Cancer has a high incidence and mortality rate worldwide, which continues to grow as millions of people are diagnosed annually. Metastatic disease caused by cancer is largely responsible for the mortality rates, thus early detection of metastatic tumours can improve prognosis. However, a large number of patients will also present with micrometastasis tumours which are often missed, as conventional medical imaging modalities are unable to detect micrometastases due to the lack of specificity and sensitivity. Recent advances in radiochemistry and the development of nucleic acid based targeting molecules, have led to the development of novel agents for use in cancer diagnostics. Monoclonal antibodies may also be used, however, they have inherent issues, such as toxicity, cost, unspecified binding and their clinical use can be controversial. Aptamers are a class of single-stranded RNA or DNA ligands with high specificity, binding affinity and selectivity for a target, which makes them promising for molecular biomarker imaging. Aptamers are presented as being a superior choice over antibodies because of high binding affinity and pH stability, amongst other factors. A number of aptamers directed to cancer cell markers (breast, lung, colon, glioblastoma, melanoma) have been radiolabelled and characterised to date. Further work is ongoing to develop these for clinical applications.

Overexpression of α (1,6) fucosyltransferase in the development of castration-resistant prostate cancer cells

Glycosylation is recognized as one of the most common modifications on proteins. Recent studies have shown that aberrant expression of α (1,6) fucosyltransferase (FUT8), which catalyzes the transfer of fucose from GDP-fucose to core-GlcNAc of the N-linked glycoproteins, modulates cellular behavior that could lead to the development of aggressive prostate cancer. While the relationship between the abnormal expression of FUT8 and glycoprotein fucosylation in different prostate cancer cells has been demonstrated, there is no evidence that shows dysregulated fucosylation might be involved in prostate cancer progression from androgen-dependent to castration-resistant prostate cancer. In this study, using a proteomics approach, we analyzed androgen-dependent and androgen-resistant LAPC4 cells and identified FUT8 to be significantly overexpressed in the androgen-resistant LAPC4 cells. These findings were independently confirmed in LAPC4 cells that were treated with non-steroidal anti-androgen (bicalutamide) and in the in vivo castrated tumor xenograft models. Similarly, we also demonstrated that overexpression of FUT8 might be responsible for the decreased PSA expression in prostate cancer specimens. To our knowledge, this is the first study reporting the functional role of fucosylated enzyme in the development of castration-resistant prostate cancer.

Polyglutamine androgen receptor-mediated neuromuscular disease

An expanded polyglutamine (polyQ) tract at the amino-terminus of the androgen receptor (AR) confers toxic properties responsible for neuronal and non-neuronal degeneration in spinal and bulbar muscular atrophy (SBMA), one of nine polyQ expansion diseases. Both lower motor neurons and peripheral tissues, including skeletal muscle, are affected, supporting the notion that SBMA is not a pure motor neuron disease but a degenerative disorder of the neuromuscular system. Here, we review experimental evidence demonstrating both nerve and muscle degeneration in SBMA model systems and patients. We propose that polyQ AR toxicity targets these components in a time-dependent fashion, with muscle pathology predominating early and motor neuron loss becoming more significant at late stages. This model of pathogenesis has important therapeutic implications, suggesting that symptoms arising from degeneration of nerve or muscle predominate at different points and that directed interventions targeting these components will be variably effective depending upon disease progression.

Targeting Androgen Receptor Activation Function-1 with EPI to Overcome Resistance Mechanisms in Castration-Resistant Prostate Cancer

PURPOSE

Persistent androgen receptor (AR) transcriptional activity is clinically evident in castration-resistant prostate cancer (CRPC). Therefore, AR remains as a viable therapeutic target for CRPC. All current hormonal therapies target the C-terminus ligand-binding domain (LBD) of AR. By using EPI to target AR activation function-1 (AF-1), in the N-terminal domain that is essential for AR transactivation, we evaluate the ability of EPI to overcome several clinically relevant AR-related mechanisms of resistance.

EXPERIMENTAL DESIGN

To study the effect of EPI on AR transcriptional activity against overexpressed coactivators, such as SRC1-3 and p300, luciferase reporter assays were performed using LNCaP cells. AR-negative COS-1 cells were employed for reporter assays to examine whether the length of polyglutamine tract affects inhibition by EPI. The effect of EPI on constitutively active AR splice variants was studied in LNCaP95 cells, which express AR-V7 variant. To evaluate the effect of EPI on the proliferation of LNCaP95 cells, we performed in vitro BrdUrd incorporation assay and in vivo studies using xenografts in mice.

RESULTS

EPI effectively overcame several molecular alterations underlying aberrant AR activity, including overexpressed coactivators, AR gain-of-function mutations, and constitutively active AR-V7. EPI inhibited AR transcriptional activity regardless of the length of polyglutamine tract. Importantly, EPI significantly inhibited the in vitro and in vivo proliferation of LNCaP95 prostate cancer cells, which are androgen independent and enzalutamide resistant.

CONCLUSIONS

These findings support EPI as a promising therapeutic agent to treat CRPC, particularly against tumors driven by constitutively active AR splice variants that are resistant to LBD-targeting drugs. Clin Cancer Res; 22(17); 4466-77. ©2016 AACRSee related commentary by Sharp et al., p. 4280.

The AR/NCOA1 axis regulates prostate cancer migration by involvement of PRKD1

Due to the urgent need for new prostate cancer (PCa) therapies, the role of androgen receptor (AR)-interacting proteins should be investigated. In this study we aimed to address whether the AR coactivator nuclear receptor coactivator 1 (NCOA1) is involved in PCa progression. Therefore, we tested the effect of long-term NCOA1 knockdown on processes relevant to metastasis formation. [(3)H]-thymidine incorporation assays revealed a reduced proliferation rate in AR-positive MDA PCa 2b and LNCaP cells upon knockdown of NCOA1, whereas AR-negative PC3 cells were not affected. Furthermore, Boyden chamber assays showed a strong decrease in migration and invasion upon NCOA1 knockdown, independently of the cell line's AR status. In order to understand the mechanistic reasons for these changes, transcriptome analysis using cDNA microarrays was performed. Protein kinase D1 (PRKD1) was found to be prominently up-regulated by NCOA1 knockdown in MDA PCa 2b, but not in PC3 cells. Inhibition of PRKD1 reverted the reduced migratory potential caused by NCOA1 knockdown. Furthermore, PRKD1 was negatively regulated by AR. Immunohistochemical staining of PCa patient samples revealed a strong increase in NCOA1 expression in primary tumors compared with normal prostate tissue, while no final conclusion could be drawn for PRKD1 expression in tumor specimens. Thus, our findings directly associate the AR/NCOA1 complex with PRKD1 regulation and cellular migration and support the concept of therapeutic inhibition of NCOA1 in PCa.

Role of Nuclear Receptors in Central Nervous System Development and Associated Diseases

The nuclear hormone receptor (NHR) superfamily is composed of a wide range of receptors involved in a myriad of important biological processes, including development, growth, metabolism, and maintenance. Regulation of such wide variety of functions requires a complex system of gene regulation that includes interaction with transcription factors, chromatin-modifying complex, and the proper recognition of ligands. NHRs are able to coordinate the expression of genes in numerous pathways simultaneously. This review focuses on the role of nuclear receptors in the central nervous system and, in particular, their role in regulating the proper development and function of the brain and the eye. In addition, the review highlights the impact of mutations in NHRs on a spectrum of human diseases from autism to retinal degeneration.

Polymorphisms and genes associated with puberty in heifers

Puberty onset is a multifactorial process influenced by genetic determinants and environmental conditions, especially nutritional status. Genes, genetic variations, and regulatory networks compose the molecular basis of achieving puberty. In this article, we reviewed the discovery of multiple polymorphisms and genes associated with heifer puberty phenotypes and discuss the opportunities to use this evolving knowledge of genetic determinants for breeding early pubertal Bos indicus-influenced cattle. The discovery of polymorphisms and genes was mainly achieved through candidate gene studies, quantitative trait loci analyses, genome-wide association studies, and recently, global gene expression studies (transcriptome). These studies are recapitulated and summarized in the current review.

Moving Beyond the Androgen Receptor (AR): Targeting AR-Interacting Proteins to Treat Prostate Cancer

Medical or surgical castration serves as the backbone of systemic therapy for advanced and metastatic prostate cancer, taking advantage of the importance of androgen signaling in this disease. Unfortunately, resistance to castration emerges almost universally. Despite the development and approval of new and more potent androgen synthesis inhibitors and androgen receptor (AR) antagonists, prostate cancers continue to develop resistance to these therapeutics, while often maintaining their dependence on the AR signaling axis. This highlights the need for innovative therapeutic approaches that aim to continue disrupting AR downstream signaling but are orthogonal to directly targeting the AR itself. In this review, we discuss the preclinical research that has been done, as well as clinical trials for prostate cancer, on inhibiting several important families of AR-interacting proteins, including chaperones (such as heat shock protein 90 (HSP90) and FKBP52), pioneer factors (including forkhead box protein A1 (FOXA1) and GATA-2), and AR transcriptional coregulators such as the p160 steroid receptor coactivators (SRCs) SRC-1, SRC-2, SRC-3, as well as lysine deacetylases (KDACs) and lysine acetyltransferases (KATs). Researching the effect of-and developing new therapeutic agents that target-the AR signaling axis is critical to advancing our understanding of prostate cancer biology, to continue to improve treatments for prostate cancer and for overcoming castration resistance.

MiR137 is an androgen regulated repressor of an extended network of transcriptional coregulators

Androgens and the androgen receptor (AR) play crucial roles in male development and the pathogenesis and progression of prostate cancer (PCa). The AR functions as a ligand dependent transcription factor which recruits multiple enzymatically distinct epigenetic coregulators to facilitate transcriptional regulation in response to androgens. Over-expression of AR coregulators is implicated in cancer. We have shown that over-expression of KDM1A, an AR coregulator, contributes to PCa recurrence by promoting VEGFA expression. However the mechanism(s) whereby AR coregulators are increased in PCa remain poorly understood. In this study we show that the microRNA hsa-miR-137 (miR137) tumor suppressor regulates expression of an extended network of transcriptional coregulators including KDM1A/LSD1/AOF1, KDM2A/JHDM1A/FBXL11, KDM4A/JMJD2A, KDM5B JARID1B/PLU1, KDM7A/JHDM1D/PHF8, MED1/TRAP220/DRIP205 and NCoA2/SRC2/TIF2. We show that expression of miR137 is increased by androgen in LnCaP androgen PCa responsive cells and that the miR137 locus is epigenetically silenced in androgen LnCaP:C4-2 and PC3 independent PCa cells. In addition, we found that restoration of miR137 expression down-regulates expression of VEGFA, an AR target gene, which suggests a role of miR137 loss also in cancer angiogenesis. Finally we show functional inhibition of miR137 function enhanced androgen induction of PSA/KLK3 expression. Our data indicate that miR137 functions as an androgen regulated suppressor of androgen signaling by modulating expression of an extended network of transcriptional coregulators. Therefore, we propose that epigenetic silencing of miR137 is an important event in promoting androgen signaling during prostate carcinogenesis and progression.

Preserved fertility in a patient with gynecomastia associated with the p.Pro695Ser mutation in the androgen receptor

The androgen insensitivity syndrome (AIS) is described as a dysfunction of the androgen receptor (AR) in 46,XY individuals, which can be associated with mutations in the AR gene or can be due to unknown mechanisms. Different mutations in AIS generally cause variable phenotypes that range from a complete hormone resistance to a mild form usually associated with male infertility. The purpose of this study was to search for mutations in the AR gene in a fertile man with gynecomastia and to evaluate the influence of the mutation on the AR transactivation ability. Sequencing of the AR gene revealed the p.Pro695Ser mutation. It is located within the AR ligand-binding domain. Bioinformatics analysis indicated a deleterious role, which was verified after testing transactivation activity and N-/C-terminal (N/C) interaction by in vitro expression of a reporter gene and 2-hybrid assays. p.Pro695Ser showed low levels of both transactivation activity and N/C interaction at low dihydrotestosterone (DHT) conditions. As the ligand concentration increased, both transactivation activity and N/C interaction also increased and reached normal levels. Therefore, this study provides functional insights for the p.Pro695Ser mutation described here for the first time in a patient with mild AIS. The expression profile of p.Pro695Ser not only correlates to the patient's phenotype, but also suggests that a high-dose DHT therapy may overcome the functional deficit of the mutant AR.

Claudin 4 expression in triple-negative breast cancer: correlation with androgen receptors and Ki-67 expression

Breast cancer is the most common malignancy in women and the leading cause of cancer mortality worldwide. Triple-negative breast cancer (TNBC) is an important phenotype of breast cancer that accounts for a relatively small number of breast cancer cases but still represent a focus of increasing interest at the clinical, biological, and epidemiological level. Claudins are the major component of the tight junction, and only a few studies have addressed the role of claudins in breast cancer, especially TNBC. Androgen receptors (ARs), as members of the nuclear receptor superfamily, are known to be involved in a complex network of signaling pathways that collectively regulate cell proliferation. However, roles of AR in breast cancer development and progression have not been very clearly understood. The proliferation marker Ki-67 has been confirmed as an independent predictive and prognostic factor in early breast cancer. The aims of this study are to identify the clinicopathologic associations and prognostic value of claudin 4 expression in TNBC and to correlate claudin 4 expression with AR status and Ki-67 expression. Paraffin blocks obtained from 56 female patients with triple-negative primary invasive ductal breast carcinomas were analyzed for claudin 4, AR, and Ki-67 immunohistochemical expression. High levels of claudin 4 expression were detected in 66.1% of TNBC cases. There was a significant positive correlation with age, tumor size, grade, nodal status, metastasis, and Ki-67 expression (all P < .05) and negative correlation with AR status (P < .001). Androgen receptor showed positivity in 29 cases (51.78%). There was a statistical negative correlation with the all the studied clinicopathologic parameters, claudin 4 and Ki-67 expression. High claudin 4 expression, negative AR expression, and high Ki-67 index would provide a strong prognostic power to differentiate the patients with worse outcome among TNBC patients. Moreover, target treatment for TNBC cells expressing claudin 4 or AR enriched would be valuable for future therapies.

MicroRNA expressions associated with progression of prostate cancer cells to antiandrogen therapy resistance

Background

Development of resistance to androgen deprivation therapy (ADT) is a major obstacle for the management of advanced prostate cancer. Therapies with androgen receptor (AR) antagonists and androgen withdrawal initially regress tumors but development of compensatory mechanisms including AR bypass signaling leads to re-growth of tumors. MicroRNAs (miRNAs) are small regulatory RNAs that are involved in maintenance of cell homeostasis but are often altered in tumor cells.

Results

In this study, we determined the association of genome wide miRNA expression (1113 unique miRNAs) with development of resistance to ADT. We used androgen sensitive prostate cancer cells that progressed to ADT and AR antagonist Casodex (CDX) resistance upon androgen withdrawal and treatment with CDX. Validation of expression of a subset of 100 miRNAs led to identification of 43 miRNAs that are significantly altered during progression of cells to treatment resistance. We also show a correlation of altered expression of 10 proteins targeted by some of these miRNAs in these cells.

Conclusions

We conclude that dynamic alterations in miRNA expression occur early on during androgen deprivation therapy, and androgen receptor blockade. The cumulative effect of these altered miRNA expression profiles is the temporal modulation of multiple signaling pathways promoting survival and acquisition of resistance. These early events are driving the transition to castration resistance and cannot be studied in already developed CRPC cell lines or tissues. Furthermore our results can be used a prognostic marker of cancers with a potential to be resistant to ADT.

The transcription intermediary factor 1β coactivates the androgen receptor

The androgen receptor (AR) is a ligand-inducible transcription factor. Its transcription activation domain consists of the two transcription activation units called Tau-1 and Tau- 5. Tau-5 interacts with p160 coactivators like the transcription intermediary factor 2 (TIF2), which in their turn recruit histone modifiers and chromatin-remodelling complexes. The mechanism of action of Tau-1, however, remains elusive. Here, we demonstrate that transcription intermediary factor 1β (TIF1β) can induce the activity of the AR up to five fold when tested in vitro. Although there is no evidence for direct interactions between TIF1β and AR, mutation studies show that the activity of TIF1β depends on the integrity of Tau-1 in AR on the one hand, and the so-called tripartite motif domain in TIF1β on the other. Surprisingly, the coactivation by TIF1β via Tau-1 seems additive rather than cooperative with the AR coactivation by TIF2. Some mutations naturally occurring in androgen-insensitivity syndrome patients that reside in Tau-1 seem to impair the TIF1β coactivation of the AR, indicating that TIF1β could also be relevant for the in vivo androgen response in humans. Moreover, since TIF1β is well expressed in prostate cancer cells, its functional interaction with androgen signalling could in the long run be a therapeutic target for this disease.

Visualising androgen receptor activity in male and female mice

Androgens, required for normal development and fertility of males and females, have vital roles in the reproductive tract, brain, cardiovascular system, smooth muscle and bone. Androgens function via the androgen receptor (AR), a ligand-dependent transcription factor. To assay and localise AR activity in vivo we generated the transgenic “ARE-Luc” mouse, expressing a luciferase reporter gene under the control of activated endogenous AR. In vivo imaging of androgen-mediated luciferase activity revealed several strongly expressing tissues in the male mouse as expected and also in certain female tissues. In males the testes, prostate, seminal vesicles and bone marrow all showed high AR activity. In females, strong activity was seen in the ovaries, uterus, omentum tissue and mammary glands. In both sexes AR expression and activity was also found in salivary glands, the eye (and associated glands), adipose tissue, spleen and, notably, regions of the brain. Luciferase protein expression was found in the same cell layers as androgen receptor expression. Additionally, mouse AR expression and activity correlated well with AR expression in human tissues. The anti-androgen bicalutamide reduced luciferase signal in all tissues. Our model demonstrates that androgens can act in these tissues directly via AR, rather than exclusively via androgen aromatisation to estrogens and activation of the estrogen receptor. Additionally, it visually demonstrates the fundamental importance of AR signalling outside the normal role in the reproductive organs. This model represents an important tool for physiological and developmental analysis of androgen signalling, and for characterization of known and novel androgenic or antiandrogenic compounds.

Targeting of Androgen Receptor Expression by Andro-miRs as Novel Adjunctive Therapeutics in Prostate Cancer

Prostate cancer begins as an androgen-responsive disease. However, subsequent accumulation of multiple sequential genetic and epigenetic alterations transforms the disease into an aggressive, castration-resistant prostate cancer (CRPC). The monoallelic Androgen Receptor (AR) is associated with the onset, growth and development of Prostate cancer. The AR is a ligand-dependent transcription factor, and the targeting of androgen- and AR-signaling axis remains the primary therapeutic option for Prostate cancer (PCa) treatment. A durable and functional disruption of AR signaling pathways combining both traditional and novel therapeutics is likely to provide better treatment options for CRPC. Recent work has indicated that expression of AR is modulated at the posttranscriptional level by regulatory miRNAs. Due to a relatively long 3’ untranslated region (UTR) of AR mRNA, the posttranscription expression is likely to be regulated by hundreds of miRNAs in normal as well as in disease state. The main objective of the article is to offer a thought-provoking concept of “andro-miRs” and their potential application in AR gene expression targeting. This new paradigm for targeting constitutively active AR and its tumor specific splicing isoforms using andro-miRs may pave the way for a novel adjunctive therapy and improved treatment of CRPC.

Androgen receptor phosphorylation at serine 515 by Cdk1 predicts biochemical relapse in prostate cancer patients

Background:

Prostate cancer cell growth is dependent upon androgen receptor (AR) activation, which is regulated by specific kinases. The aim of the current study is to establish if AR phosphorylation by Cdk1 or ERK1/2 is of prognostic significance.

Methods:

Scansite 2.0 was utilised to predict which AR sites are phosphorylated by Cdk1 and ERK1/2. Immunohistochemistry for these sites was then performed on 90 hormone-naive prostate cancer specimens. The interaction between Cdk1/ERK1/2 and AR phosphorylation was investigated in vitro using LNCaP cells.

Results:

Phosphorylation of AR at serine 515 (pAR^S515) and PSA at diagnosis were independently associated with decreased time to biochemical relapse. Cdk1 and pCdk1¹⁶¹, but not ERK1/2, correlated with pAR^S515. High expression of pAR^S515 in patients with a PSA at diagnosis of ⩽20 ng ml⁻¹ was associated with shorter time to biochemical relapse (P=0.019). This translated into a reduction in disease-specific survival (10-year survival, 38.1% vs 100%, P<0.001). In vitro studies demonstrated that treatment with Roscovitine (a Cdk inhibitor) caused a reduction in pCdk1¹⁶¹ expression, pAR^S515expression and cellular proliferation.

Conclusion:

In prostate cancer patients with PSA at diagnosis of ⩽20 ng ml⁻¹, phosphorylation of AR at serine 515 by Cdk1 may be an independent prognostic marker.

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

Androgen receptor (AR) is involved in the development and progression of prostate cancers. However, the mechanisms by which this occurs remain incompletely understood. In previous reports, chicken ovalbumin upstream promoter-transcription factor II (COUP-TF II) has been suggested to play a role in the development of cancers. In the present study, we explored a putative role of COUP-TF II in prostate cancers by investigating its effect on cell proliferation and a cross-talk between COUP-TF II and AR. Overexpression of COUP-TF II results in the inhibition of androgen-dependent proliferation of prostate cancer cells. Further studies show that COUP-TF II functions as a corepressor of AR. It represses AR transactivation on target promoters containing the androgen response element (ARE) in a dose-dependent manner. In addition, COUP-TF II interacts physically with AR in vitro and in vivo. It binds to both the DNA binding domain (DBD) and the ligand-binding domain (LBD) of AR and disrupts the N/C terminal interaction of AR. Furthermore, COUP-TF II competes with coactivators such as ARA70, SRC-1, and GRIP1 to modulate AR transactivation as well as inhibiting the recruitment of AR to its ARE-containing target promoter. Taken together, our findings suggest that COUP-TF II is a novel corepressor of AR, and provide an insight into the role of COUP-TF II in prostate cancers.

Androgen receptor coregulators: recruitment via the coactivator binding groove

Androgens are key regulators of male sexual differentiation and essential for development and maintenance of male reproductive tissues. The androgens testosterone and dihydrotestosterone mediate their effect by binding to, and activation of the androgen receptor (AR). Upon activation, the AR is able to recognize specific DNA sequences in gene promoters and enhancers from where it recruits coregulators to orchestrate chromatin remodeling and transcription regulation. The number of proteins that bind to the AR has surpassed 200 and many of them enhance (coactivator) or repress (corepressor) its transactivating capacity. For most of these coregulators, their AR binding interface and their exact mode of action still needs to be elucidated, but for some of the more classical coactivators and corepressors, we gained insight in their working mechanisms. Of particular interest are specific sequences (LxxLL and FxxLF-like motifs) in a subset of coactivators that interact with the AR via a coactivator binding groove in the ligand-binding domain. As compared to other steroid receptors, the conformation of the AR coactivator binding pocket is unique and preferentially binds FxxLF-like motifs. This predisposition is expected to contribute to the regulation of specific sets of target genes via recruitment of selected coregulators. This review provides an overview of these (inter)actions with a focus on the unique characteristics of the AR coactivator binding groove.

Allosteric modulators of steroid hormone receptors: structural dynamics and gene regulation

Steroid hormones are synthesized from cholesterol primarily in the adrenal gland and the gonads and play vital roles in normal physiology, the control of development, differentiation, metabolic homeostasis, and reproduction. The actions of these small lipophilic molecules are mediated by intracellular receptor proteins. It is just over 25 yr since the first cDNA for steroid receptors were cloned, a development that led to the birth of a superfamily of ligand-activated transcription factors: the nuclear receptors. The receptor proteins share structurally and functionally related ligand binding and DNA-binding domains but possess distinct N-terminal domains and hinge regions that are intrinsically disordered. Since the original cloning experiments, considerable progress has been made in our understanding of the structure, mechanisms of action, and biology of this important class of ligand-activated transcription factors. In recent years, there has been interest in the structural plasticity and function of the N-terminal domain of steroid hormone receptors and in the allosteric regulation of protein folding and function in response to hormone, DNA response element architecture, and coregulatory protein binding partners. The N-terminal domain can exist as an ensemble of conformers, having more or less structure, which prime this region of the receptor to rapidly respond to changes in the intracellular environment through hormone binding and posttranslation modifications. In this review, we address the question of receptor structure and function dynamics with particular emphasis on the structurally flexible N-terminal domain, intra- and interdomain communications, and the allosteric regulation of receptor action.

The impact of point mutations in the human androgen receptor: classification of mutations on the basis of transcriptional activity

Androgen receptor mediated signaling drives prostate cancer cell growth and survival. Mutations within the receptor occur infrequently in prostate cancer prior to hormonal therapy but become prevalent in incurable androgen independent and metastatic tumors. Despite the determining role played by the androgen receptor in all stages of prostate cancer progression, there is a conspicuous dearth of comparable data on the consequences of mutations. In order to remedy this omission, we have combined an expansive study of forty five mutations which are predominantly associated with high Gleason scores and metastatic tumors, and span the entire length of the receptor, with a literature review of the mutations under investigation. We report the discovery of a novel prevalent class of androgen receptor mutation that possesses loss of function at low levels of androgen yet transforms to a gain of function at physiological levels. Importantly, mutations introducing constitutive gain of function are uncommon, with the majority of mutations leading to either loss of function or no significant change from wild-type activity. Therefore, the widely accepted supposition that androgen receptor mutations in prostate cancer result in gain of function is appealing, but mistaken. In addition, the transcriptional outcome of some mutations is dependent upon the androgen receptor responsive element. We discuss the consequences of these findings and the role of androgen receptor mutations for prostate cancer progression and current treatment options.

Folding of the glucocorticoid receptor N-terminal transactivation function: dynamics and regulation

The glucocorticoid receptor (GR) mediates biological effects of glucocorticoids at the level of gene regulation, and plays important roles in many aspects of physiology. In recent years, it has become quite evident that GR behaves very dynamically, controlled by its reversible interactions with a variety of coregulatory proteins at various DNA and non-DNA sites. The N-terminal activation function domain (AF1) of the GR exists in an intrinsically disordered (ID) state, which promotes molecular recognition by providing surfaces capable of binding specific target molecules. Several studies suggest that when in action, the GR AF1 gains structure. Thus, it is hypothesized that the GR AF1 domain may be structured in vivo, at least when directly involved in transcriptional activation. Our recent work supports this conclusion. We propose that by allowing AF1 to rapidly and reversibly adopt various configurations through structural arrangements, AF1 can create protein surfaces that are readily available for selective binding to coregulatory proteins, resulting in GR-mediated transcriptional regulation of target genes.

The Drosophila juvenile hormone receptor candidates methoprene-tolerant (MET) and germ cell-expressed (GCE) utilize a conserved LIXXL motif to bind the FTZ-F1 nuclear receptor

Juvenile hormone (JH) has been implicated in many developmental processes in holometabolous insects, but its mechanism of signaling remains controversial. We previously found that in Drosophila Schneider 2 cells, the nuclear receptor FTZ-F1 is required for activation of the E75A gene by JH. Here, we utilized insect two-hybrid assays to show that FTZ-F1 interacts with two JH receptor candidates, the bHLH-PAS paralogs MET and GCE, in a JH-dependent manner. These interactions are severely reduced when helix 12 of the FTZ-F1 activation function 2 (AF2) is removed, implicating AF2 as an interacting site. Through homology modeling, we found that MET and GCE possess a C-terminal α-helix featuring a conserved motif LIXXL that represents a novel nuclear receptor (NR) box. Docking simulations supported by two-hybrid experiments revealed that FTZ-F1·MET and FTZ-F1·GCE heterodimer formation involves a typical NR box-AF2 interaction but does not require the canonical charge clamp residues of FTZ-F1 and relies primarily on hydrophobic contacts, including a unique interaction with helix 4. Moreover, we identified paralog-specific features, including a secondary interaction site found only in MET. Our findings suggest that a novel NR box enables MET and GCE to interact JH-dependently with the AF2 of FTZ-F1.

Molecular alterations during progression of prostate cancer to androgen independence

BACKGROUND

Prostate cancer is the most commonly diagnosed cancer among men in North America and is a leading cause of death. Standard treatments include androgen deprivation therapy, which leads to improved clinical outcomes. However, over time, most tumors become androgen independent and no longer respond to hormonal therapies. Several mechanisms have been implicated in the progression of prostate cancer to androgen independence.

CONTENT

Most tumors that have become androgen independent still rely on androgen receptor (AR) signaling. Mechanisms that enhance AR signaling in androgen-depleted conditions include: AR gene amplification, AR mutations, changes in the balance of AR cofactors, increases in steroidogenic precursors, and activation via "outlaw" pathways. Along with AR signaling, various other AR-independent "bypass" pathways have been shown to operate aberrantly during androgen independence. Changes in the epigenetic signatures and microRNA concentrations have also been implicated in the development of androgen-independent prostate cancer.

SUMMARY

Understanding of the molecular mechanisms that lead to the development of androgen-independent prostate cancer will allow for improved therapeutic strategies that target key pathways and molecules that are essential for these cells to survive.

The role of androgen receptor mutations in prostate cancer progression

Prostate tumour growth is almost always dependent upon the androgen receptor pathway and hence therapies aimed at blocking this signalling axis are useful tools in the management of this disease. Unfortunately such therapies invariably fail; and the tumour progresses to an “androgen-independent” stage. In such cases androgen receptor expression is almost always maintained and much evidence exists to suggest that it may still be driving growth. One mechanism by which the receptor is thought to remain active is mutation. This review summarises the present data on androgen receptor mutations in prostate cancer, and how such substitutions offer a growth advantage by affecting cofactor interactions or by reducing ligand specificity. Such alterations appear to have a subsequent effect upon gene expression suggesting that tumours may “behave” differently dependent upon the ligand promoting growth and if a mutation is present.

A single nucleotide polymorphism-derived regulatory gene network underlying puberty in 2 tropical breeds of beef cattle

Harsh tropical environments impose serious challenges on poorly adapted species. In beef cattle, tropical adaptation in the form of temperature and disease resistance, coupled with acclimatization to seasonal and limited forage, comes at a cost to production efficiency. Prominent among these costs is delayed onset of puberty, a challenging phenotype to manipulate through traditional breeding mechanisms. Recently, system biology approaches, including gene networks, have been applied to the genetic dissection of complex phenotypes. We aimed at developing and studying gene networks underlying cattle puberty. Our starting material comprises the association results of ~50,000 SNP on 22 traits, including age at puberty, and 2 cattle breed populations: Brahman (n = 843) and Tropical Composite (n = 866). We defined age at puberty as the age at first corpus luteum (AGECL). By capturing the genes harboring mutations minimally associated (P < 0.05) to AGECL or to a set of traits related with AGECL, we derived a gene network for each breed separately and a third network for the combined data set. At the intersection of the 3 networks, we identified candidate genes and pathways that were common to both breeds. Resulting from these analyses, we identified an enrichment of genes involved in axon guidance, cell adhesion, ErbB signaling, and glutamate activity, pathways that are known to affect pulsatile release of GnRH, which is necessary for the onset of puberty. Furthermore, we employed network connectivity and centrality parameters along with a regulatory impact factor metric to identify the key transcription factors (TF) responsible for the molecular regulation of puberty. As a novel finding, we report 5 TF (HIVEP3, TOX, EYA1, NCOA2, and ZFHX4) located in the network intersecting both breeds and interacting with other TF, forming a regulatory network that harmonizes with the recent literature of puberty. Finally, we support our network predictions with evidence derived from gene expression in hypothalamic tissue of adult cows.

Steroid hormone receptors in cancer development: a target for cancer therapeutics

The steroid hormone receptors (SHRs) are ligand-dependent intracellular transcription factors that are known to influence the development and growth of many human cancers. SHRs pass signals from a steroid/hormone to the target genes by interacting with specific response element DNA sequences and various coregulatory proteins that consists of activators and/or corepressors. Disruptions in physiological functions of SHRs leads to several types of malignancies such as breast cancer, leukemia and lymphoma, prostate cancer, ovarian cancer, and lung cancer among others. Steroids/hormones/SHRs and their coregulators have opened up a unique window for novel steroid-based targeted therapies for cancer. Thus, dysregulation of SHR signaling in cancers compared with normal tissues can be exploited to target drugs that prevent and treat human cancers. In recent years, hormonal therapy has made a major contribution to the treatment of several cancers including reduced recurrence rates and longer survival rates. Development of various steroid receptor modulators and their potential therapeutic efficacies has provided us a great opportunity to effectively manage diseases like cancer in future. In this review article, we have summarized up-to-date knowledge of the role of SHRs in the development and progression of cancers, and potential endocrine-based therapeutic approaches to tackle these diseases.