Androgen Receptor Target Research Articles

MED12 Mutations Promote Castration Resistant Prostate Cancer Through Hyper‐activated SHH Signaling

Prostate cancer is the most common malignancy and the second leading cause of cancer associated deaths among US men. As an androgen-driven disease, prostate cancer is critically dependent upon androgen receptor (AR) signaling. Accordingly, most prostate cancer patients respond very well to androgen deprivation therapy. The current problem lies with the fact that nearly all patients progress to a lethal form of the disease after androgen deprivation therapy known as castration resistant prostate cancer (CRPC). Once patients reach the stage of CRPC, treatment options are frustratingly limited and average survival times range from two to three years only. Thus, there is a compelling need to develop effective treatments for patients suffering from CRPC. Sonic hedgehog (SHH) signaling is a stromal-epithelial interacting pathway that is critical for prostate development and cell growth. SHH signaling is induced by androgen deprivation thereby leading to re-activation of AR target genes to promote prostate cancer cell growth in the absence of androgens. Furthermore, AR interacts with GLI proteins, downstream effectors in the SHH pathway. Therefore, GLI3-dependent SHH signaling in androgen deprived cells could promote re-activation of AR target genes and consequently lead to CRPC. It is currently unknown how GLI3-dependent SHH signaling is induced in CRPC. Several studies have found that MED12, a subunit of Mediator, is commonly mutated in prostate cancer and, interestingly, MED12 has been shown to play a critical role in restricting GLI3-dependent SHH signaling. We therefore hypothesize that MED12 mutations promote GLI3-dependent SHH signaling in prostate cancer to drive progression towards CRPC. We generated stable MED12 knockdown cells, which likely recapitulates a MED12 mutant setting, followed by proliferation and qPCR assays in androgen replete and androgen deprived conditions to test our hypothesis. Our results show that MED12 knockdown promotes prostate cancer growth specifically in an androgen deprived setting and that this hyper-active growth is dependent upon GLI3. Furthermore, we also show that GLI3 target genes are sharply upregulated when MED12 expression is low and androgens are absent. The collective results of our study therefore indicate that prostate cancer patients with MED12 mutations could relapse to CRPC after androgen deprivation therapy by hyperactivating the GLI3 dependent SHH signaling pathway. Importantly, our results thus suggest that therapeutic agents that target the SHH signaling pathway could prove to be beneficial for MED12 mutant prostate cancer patients.

Targeting ADT-Induced Activation of the E3 Ubiquitin Ligase Siah2 to Delay the Occurrence of Castration-Resistant Prostate Cancer.

Siah2 is an E3 ubiquitin ligase that targets androgen receptor (AR) and plays an important role in the development of castration-resistant prostate cancer (CRPC). However, the regulation of Siah2 in prostate cancer (PCa) is largely unknown. In this study, we used AR-dependent and -independent cells lines to investigate the cellular roles of AR and androgen deprivation therapy (ADT) on Siah2 protein levels and E3 ligase activity using Western blotting and co-immunoprecipitation. We also validated our findings using patient samples taken before and after ADT. Finally, we used xenograft tumor models to test the effects of ADT combined with vitamin K3 (Vit K3) on tumor growth in vivo. Our results showed that AR stabilizes Siah2 protein by attenuating its self-ubiquitination and auto-degradation, likely by blocking its E3 ubiquitin ligase activity. Conversely, ADT decreased Siah2 protein expression but enhanced its E3 ligase activity in PCa cells. Notably, the findings that ADT decreasing Siah2 protein expression were verified in a series of paired PCa samples from the same patient. Additionally, we found that ADT-induced Siah2 activation could be abolished by Vit K3. Strikingly, ADT combined with Vit K3 treatment delayed the occurrence of CRPC and dramatically inhibited the growth of tumor xenografts compared with ADT treatment alone. AR is an inhibitor of Siah2 in PCa, and ADT leads to the continuous activation of Siah2, which may contribute to CRPC. Finally, ADT+Vit K3 may be a potential approach to delay the occurrence of CRPC.

MAP3K7 Loss Drives Enhanced Androgen Signaling and Independently Confers Risk of Recurrence in Prostate Cancer with Joint Loss of CHD1.

Prostate cancer genomic subtypes that stratify aggressive disease and inform treatment decisions at the primary stage are currently limited. Previously, we functionally validated an aggressive subtype present in 15% of prostate cancer characterized by dual deletion of MAP3K7 and CHD1. Recent studies in the field have focused on deletion of CHD1 and its role in androgen receptor (AR) chromatin distribution and resistance to AR-targeted therapy; however, CHD1 is rarely lost without codeletion of MAP3K7. Here, we show that in the clinically relevant context of co-loss of MAP3K7 and CHD1 there are significant, collective changes to aspects of AR signaling. Although CHD1 loss mainly impacts the expansion of the AR cistrome, loss of MAP3K7 drives increased AR target gene expression. Prostate cancer cell line models engineered to cosuppress MAP3K7 and CHD1 also demonstrated increased AR-v7 expression and resistance to the AR-targeting drug enzalutamide. Furthermore, we determined that low protein expression of both genes is significantly associated with biochemical recurrence (BCR) in a clinical cohort of radical prostatectomy specimens. Low MAP3K7 expression, however, was the strongest independent predictor for risk of BCR over all other tested clinicopathologic factors including CHD1 expression. Collectively, these findings illustrate the importance of MAP3K7 loss in a molecular subtype of prostate cancer that poses challenges to conventional therapeutic approaches. IMPLICATIONS: These findings strongly implicate MAP3K7 loss as a biomarker for aggressive prostate cancer with significant risk for recurrence that poses challenges for conventional androgen receptor-targeted therapies.

Androgen Receptor-Related Non-coding RNAs in Prostate Cancer.

Prostate cancer (PCa) is the second leading cause of cancer-related death among men in the United States. Androgen receptor (AR) signaling is the dominant oncogenic pathway in PCa and the main strategy of PCa treatment is to control the AR activity. A large number of patients acquire resistance to Androgen deprivation therapy (ADT) due to AR aberrant activation, resulting in castration-resistant prostate cancer (CRPC). Understanding the molecular mechanisms underlying AR signaling in the PCa is critical to identify new therapeutic targets for PCa patients. The recent advances in high-throughput RNA sequencing (RNA-seq) techniques identified an increasing number of non-coding RNAs (ncRNAs) that play critical roles through various mechanisms in different diseases. Some ncRNAs have shown great potentials as biomarkers and therapeutic targets. Many ncRNAs have been investigated to regulate PCa through direct association with AR. In this review, we aim to comprehensively summarize recent findings of the functional roles and molecular mechanisms of AR-related ncRNAs as AR regulators or targets in the progression of PCa.

The MYH9 Cytoskeletal Protein Is a Novel Corepressor of Androgen Receptors.

In the progression of castration-resistant prostate cancer (CRPC), the androgen receptor (AR) that serves as a transcription factor becomes the most remarkable molecule. The transcriptional activity of AR is regulated by various coregulators. As a result, altered expression levels, an aberrant location or activities of coregulators promote the development of prostate cancer. We describe herein results showing that compared with androgen-dependent prostate cancer (ADPC) cells, AR nuclear translocation capability is enhanced in androgen-independent prostate cancer (AIPC) cells. To gain insight into whether AR coregulators are responsible for AR translocation capability, we performed coimmunoprecipitation (CO-IP) coupled with LC-MS/MS to screen 27 previously reported AR cofactors and 46 candidate AR cofactors. Furthermore, one candidate, myosin heavy chain 9 (MYH9), was identified and verified as a novel AR cofactor. Interestingly, the distribution of MYH9 was in both the cytoplasmic and nuclear compartments yet was enriched in the nucleus when AR was knocked down by AR shRNA, suggesting that the nuclear translocation of MYH9 was negatively regulated by AR. In addition, we found that blebbistatin, an inhibitor of MYH9, not only promoted AR nuclear translocation but also enhanced the expression of the AR target gene PSA, which indicates that MYH9 represses nuclear AR signaling. Taken together, our findings reveal that MYH9 appears to be a novel corepressor of AR plays a pivotal role in the progression of CRPC.

Cross-Resistance to Abiraterone and Enzalutamide in Castration Resistance Prostate Cancer Cellular Models Is Mediated by AR Transcriptional Reactivation.

Simple SummaryProstate cancer is the second most common cancer in males. In prostate cancer cells, androgens bind and activate the intracellular mediator called Androgen Receptor that control cell proliferation and survival. Hormone deprivation therapy is administrated to reduce androgen levels and consequently tumour growth. Unfortunately, most patients develop resistance to hormone treatment over the years and novel hormonal agents, such as Abiraterone or Enzalutamide, are administered. However, many patients do not initially respond or become resistant to these drugs quickly. Firstly, we demonstrated that in hormonal sensitive human prostate cancer cells the combination therapy of Abiraterone plus Enzalutamide reduced cell growth and survival. Moreover, starting from these prostate cancer cell lines, we generated cellular models of resistance to hormonal deprivation alone or in combination with the novel hormonal agents. In all the cases, resistant cell lines restore Androgen Receptor expression, Androgen Receptor functionality, cell proliferation and migration in the absence of androgens. Importantly, these novel cellular models acquire cross-resistance to each other. These results are consistent with clinical trials in castration resistant prostate cancer patients and suggest the biological rationale to test the combination therapy of Abiraterone plus Enzalutamide as first-line treatment in hormone-sensitive prostate cancer patients before becoming hormonal resistant.Androgen deprivation therapy (ADT) and novel hormonal agents (NHAs) (Abiraterone and Enzalutamide) are the goal standard for metastatic prostate cancer (PCa) treatment. Although ADT is initially effective, a subsequent castration resistance status (CRPC) is commonly developed. The expression of androgen receptor (AR) alternative splicing isoforms (AR-V7 and AR-V9) has been associated to CRPC. However, resistance mechanisms to novel NHAs are not yet well understood. Androgen-dependent PCa cell lines were used to generate resistant models to ADT only or in combination with Abiraterone and/or Enzalutamide (concomitant models). Functional and genetic analyses were performed for each resistance model by real-time cell monitoring assays, flow cytometry and RT-qPCR. In androgen-dependent PCa cells, the administration of Abiraterone and/or Enzalutamide as first-line treatment involved a critical inhibition of AR activity associated with a significant cell growth inhibition. Genetic analyses on ADT-resistant PCa cell lines showed that the CRPC phenotype was accompanied by overexpression of AR full-length and AR target genes, but not necessarily AR-V7 and/or AR-V9 isoforms. These ADT resistant cell lines showed higher proliferation rates, migration and invasion abilities. Importantly, ADT resistance induced cross-resistance to Abiraterone and/or Enzalutamide. Similarly, concomitant models possessed an elevated expression of AR full-length and proliferation rates and acquired cross-resistance to its alternative NHA as second-line treatment.

The effects of new life-prolonging drugs for metastatic castration-resistant prostate cancer (mCRPC) patients in a real-world population.

In 2004 docetaxel was the first life-prolonging drug (LPD) registered for metastatic castration-resistant prostate cancer (mCRPC) patients. Between 2011 and 2014 new LPDs for mCRPC (cabazitaxel, abiraterone, enzalutamide, and radium-223) were introduced in the Netherlands. The objective of this study is to assess the impact of the introduction of new LPDs on treatment patterns and overall survival (OS) over time. CRPC patients diagnosed in the years 2010-2016 in the observational, retrospective CAPRI registry (20 hospitals) were included and followed up to 2018. Two subgroups were analyzed: treatment-naïve patients (subgroup 1, n = 3600) and post-docetaxel patients (subgroup 2, n = 1355). In both subgroups, the use of any LPD increased: from 57% (2010-2011) to 69% (2014-2015) in subgroup 1 and from 65% (2011-2012) to 79% (2015-2016) in subgroup 2. Chemotherapy as first mCRPC-treatment (i.e., docetaxel) and first post-docetaxel treatment (i.e., cabazitaxel or docetaxel rechallenge) decreased (46-29% and 20-9% in subgroup 1 and 2, respectively), while the use of androgen-receptor targeting treatments (ART) increased from 11% to 39% and 46% to 64% in subgroup 1 and 2, respectively. In subgroup 1, median OS (mOS) from diagnosis CRPC increased from 28.5 months to 31.0 months (p = 0.196). In subgroup 2, mOS from progression on docetaxel increased from 7.9 months to 12.5 months (p < 0.001). After multiple imputations of missing values, in multivariable cox-regression analysis with known prognostic parameters, the treatment period was independent significant for OS in subgroup 1 (2014-2015 vs. 2010-2011 with HR 0.749, p < 0.001) and subgroup 2 (2015-2016 vs. 2011-2012 with HR 0.811, p = 0.037). Since 2010, a larger proportion of mCRPC patients was treated with LPDs, which was related to an increased mOS.

Hormone-Dependent Prostate Cancers are Dependent on Rac Signaling for Growth and Survival.

Prostate cancer remains a common cause of cancer mortality in men. Initially, cancers are dependent of androgens for growth and survival. First line therapies reduce levels of circulating androgens or target the androgen receptor (AR) directly. Although most patients show durable responses, many patients eventually progress to castration-resistant prostate cancer (CRPC) creating a need for alternative treatment options. The Rac1 signaling pathway has previously been implicated as a driver of cancer initiation and disease progression. We investigated the role of HACE1, the E3 ubiquitin ligase for Rac1, in prostate cancer and found that HACE1 is commonly lost resulting in hyperactive Rac signaling leading to enhanced cellular proliferation, motility and viability. Importantly, we show that a Rac inhibitor can attenuate the growth and survival of prostate cancer cells. Rac signaling was also found to be critical in prostate cancers that express the AR. Rac inhibition in androgen dependent cells resulted in reduction of AR target gene expression suggesting that targeting Rac1 may be an alternative method for blocking the AR signaling axis. Finally, when used in combination with AR antagonists, Rac inhibition enhanced the suppression of AR target gene expression. Therefore, targeting Rac in prostate cancer has the potential to enhance the efficacy of approved AR therapies.

Overall survival of patients with metastatic castrate-resistant prostate cancer (mCRPC) who have PTEN tumor suppressor gene loss of function.

58 Background: It is estimated that more than 40% of patients with mCRPC have functional loss of phosphatase and tensin homolog (PTEN) tumor suppressor gene, which is associated with unfavorable prognosis and reduced response to androgen receptor-targeting therapy. We describe patient characteristics and survival outcomes by PTEN LOF status among patients with mCRPC in real-world clinical practice. Methods: We conducted a retrospective cohort study using data from the nationwide Flatiron Health-Foundation Medicine mCRPC Clinico-Genomic database (FH-FMI CGDB), a de-identified database linking data derived from electronic health records with genomic data derived from FMI comprehensive genomic profiling (CGP) tests. The study included patients ≥18 years old, with a primary diagnosis of mCRPC between 1/1/2013 and 6/30/2019 who underwent FMI CGP testing and who had a valid PTEN LOF status. Patients were included if their PTEN report date and mCRPC diagnosis date occurred before death or censoring. PTEN LOF status was identified via FMI’s CGP testing. Kaplan-Meier (KM) methods assessed overall survival (OS) by PTEN LOF status from the date of mCRPC diagnosis (later of metastasis and castration resistance) until death or end of study follow-up. A stratified Cox regression model was used to estimate the hazard of death. The Cox model was adjusted for age, race and sequence of metastasis/CRPC diagnoses, and was stratified by the year of mCRPC diagnosis. Adjustments to account for left-truncation and survivorship bias were made in the KM analysis and the Cox regression model. Results: Among the 458 patients who met the eligibility criteria, 174 (38%) had PTEN LOF. The majority of the study sample (76%) was diagnosed with castration-resistance after metastasis. The PTEN LOF group had a higher percentage of white patients (80% vs. 68%; p= 0.01) compared to the PTEN non-LOF group. The mean age of the study sample was 68 years, and there was no difference in mean age at diagnosis by PTEN LOF status ( p= 0.17). Based on the KM estimates adjusted for left-truncation, the median OS was 14.3 months (95% confidence interval [CI]: 11.1-19.7) in the PTEN LOF group compared to 18.3 months (95%CI: 15.5-21.5) in the PTEN non-LOF group (log-rank p= 0.049). In the multivariable Cox model, the PTEN LOF group had numerically 30% higher risk of death compared to the PTEN non-LOF group (hazard ratio = 1.30; 95% CI: 0.99-1.71; p= 0.057). Conclusions: Among real-world patients with mCRPC in the CGDB, PTEN LOF could be associated with poorer survival outcomes, potentially highlighting the unmet need among these patients. Additional studies with larger cohorts are needed to better evaluate the survival outcomes of patients with PTEN LOF. Therapeutic agents acting on the PTEN/PI3K/AKT/mTOR pathway are being tested in clinical trials, and could potentially improve outcomes in this subgroup of patients with mCRPC.

Risk of cardiovascular events in men on abiraterone or enzalutamide combined with GnRH agonists: nation-wide, population-based cohort study in Sweden

Background Men with prostate cancer (PCa) on gonadotropin-releasing hormone agonists (GnRH) have an increased risk of cardiovascular disease (CVD) compared to men with PCa not on GnRH as well as compared with PCa-free men. Whether the addition of androgen receptor targeted (ART) drugs to GnRH further increases CVD risk, remains to be fully elucidated. Material and methods We investigated risk of CVD for men with castration resistant PCa (CRPC) on GnRH plus ART; abiraterone or enzalutamide vs 5,127 and 12,079 respective matched comparator men on GnRH in Prostate Cancer data Base Sweden (PCBaSeTraject) 4.1 between 1 June 2015 and 31 December 2018. PCBaSeTraject links National Prostate Cancer Register of Sweden to other healthcare registries and demographic databases. We conducted multivariable Cox proportional hazard models adjusting for PCa risk category, Charlson comorbidity index (CCI), insulin or statin use, civil status, level of education, history of CVD events and number of CVD drugs, with any incident or fatal CVD as the outcome. Results and conclusion 1,310 men were treated with abiraterone and 3,579 with enzalutamide. In multivariable analysis, CVD risk was increased in men on abiraterone (hazard ratio (HR): 1.19; 95% confidence interval (CI): 1.03–1.38) and in men on enzalutamide (HR: 1.10; 95% CI: 1.01–1.20). Men with a recent CVD (<12 months) including both men on ART as well as comparators had a much higher probability of a new CVD vs men with no prior CVD. CVD risk was mildly increased in men with PCa on GnRH plus abiraterone or enzalutamide vs comparator men on GnRH. Residual confounding and detection bias may at least partly explain this association.

V-ATPase Inhibition Decreases Mutant Androgen Receptor Activity in Castrate-resistant Prostate Cancer.

Prostate cancer is critically dependent on androgen receptor (AR) signaling. Despite initial responsiveness to androgen deprivation, most patients with advanced prostate cancer subsequently progress to a clinically aggressive castrate-resistant prostate cancer (CRPC) phenotype, typically associated with expression of splice-variant or mutant AR forms. Although current evidence suggests that the vacuolar-ATPase (V-ATPase), a multiprotein complex that catalyzes proton transport across intracellular and plasma membranes, influences wild-type AR function, the effect of V-ATPase inhibition on variant AR function is unknown.Inhibition of V-ATPase reduced AR function in wild-type and mutant AR luciferase reporter models. In hormone-sensitive prostate cancer cell lines (LNCaP, DuCaP) and mutant AR CRPC cell lines (22Rv1, LNCaP-F877L/T878A), V-ATPase inhibition using bafilomycin-A1 and concanamycin-A reduced AR expression, and expression of AR target genes, at mRNA and protein levels. Furthermore, combining chemical V-ATPase inhibition with the AR antagonist enzalutamide resulted in a greater reduction in AR downstream target expression than enzalutamide alone in LNCaP cells. To investigate the role of individual subunit isoforms, siRNA and CRISPR-Cas9 were used to target the V1C1 subunit in 22Rv1 cells. Whereas transfection with ATP6V1C1-targeted siRNA significantly reduced AR protein levels and function, CRISPR-Cas9-mediated V1C1 knockout showed no substantial change in AR expression, but a compensatory increase in protein levels of the alternate V1C2 isoform.Overall, these results indicate that V-ATPase dysregulation is directly linked to both hormone-responsive prostate cancer and CRPC via impact on AR function. In particular, V-ATPase inhibition can reduce AR signaling regardless of mutant AR expression.

MiR-224-5p-enriched exosomes promote tumorigenesis by directly targeting androgen receptor in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common form of cancer, resulting in cancer-related deaths worldwide. Exosomes, a subclass of extracellular vesicles, are produced and secreted from various types of cells, including cancer cells. Cancer-derived exosomes can deliver nucleic acids, proteins, and lipids to provide a favorable microenvironment that supports tumor growth through enhancing cell proliferation and metastasis. Our results showed that miR-224-5p was upregulated in NSCLC patient tissues and cell lines, with a tumor-promoting phenotype. Meanwhile, exosome-derived miR-224-5p induced cell proliferation and metastasis in NSCLC and human lung cells. Moreover, we characterized the androgen receptor (AR) as a direct target of miR-224-5p. Tumor xenograft assay experiments revealed that overexpression of miR-224-5p drove NSCLC tumor growth via the suppression of AR and the mediation of epithelial-mesenchymal transition (EMT). Collectively, our results suggest that miR-224-5p-enriched exosomes promote tumorigenesis by directly targeting AR in NSCLC, which may provide novel potential therapeutic and preventive targets for NSCLC.

Computational Assessment of Combination Therapy of Androgen Receptor-Targeting Compounds.

The ligand-binding domain of the androgen receptor (AR) is a target for drugs against prostate cancer and offers three distinct binding sites for small molecules. Drugs acting on the orthosteric hormone binding site suffer from resistance mechanisms that can, in the worst case, reverse their therapeutic effect. While many allosteric ligands targeting either the activation function-2 (AF-2) or the binding function-3 (BF-3) have been reported, their potential for simultaneous administration with currently prescribed antiandrogens was disregarded. Here, we report results of 60 μs molecular dynamics simulations to investigate combinations of orthosteric and allosteric AR antagonists. Our results suggest BF-3 inhibitors to be more suitable in combination with classical antiandrogens as opposed to AF-2 inhibitors based on binding free energies and binding modes. As a mechanistic explanation for these observations, we deduced a structural adaptation of helix-12 involved in the formation of the AF-2 site by classical AR antagonists. Additionally, the changes were accompanied by an expansion of the orthosteric binding site. Considering our predictions, the selective combination of AR-targeting compounds may improve the treatment of prostate cancer.

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

Simple SummaryProstate 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.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.

MED19 alters AR occupancy and gene expression in prostate cancer cells, driving MAOA expression and growth under low androgen.

Androgen deprivation therapy (ADT) is a mainstay of prostate cancer treatment, given the dependence of prostate cells on androgen and the androgen receptor (AR). However, tumors become ADT-resistant, and there is a need to understand the mechanism. One possible mechanism is the upregulation of AR co-regulators, although only a handful have been definitively linked to disease. We previously identified the Mediator subunit MED19 as an AR co-regulator, and reported that MED19 depletion inhibits AR transcriptional activity and growth of androgen-insensitive LNCaP-abl cells. Therefore, we proposed that MED19 upregulation would promote AR activity and drive androgen-independent growth. Here, we show that stable overexpression of MED19 in androgen-dependent LNCaP cells promotes growth under conditions of androgen deprivation. To delineate the mechanism, we determined the MED19 and AR transcriptomes and cistromes in control and MED19-overexpressing LNCaP cells. We also examined genome-wide H3K27 acetylation. MED19 overexpression selectively alters AR occupancy, H3K27 acetylation, and gene expression. Under conditions of androgen deprivation, genes regulated by MED19 correspond to genes regulated by ELK1, a transcription factor that binds the AR N-terminus to induce select AR target gene expression and proliferation, and genomic sites occupied by MED19 and AR are enriched for motifs associated with ELK1. Strikingly, MED19 upregulates expression of monoamine oxidase A (MAOA), a factor that promotes prostate cancer growth. MAOA depletion reduces androgen-independent growth. MED19 and AR occupy the MAOA promoter, with MED19 overexpression enhancing AR occupancy and H3K27 acetylation. Furthermore, MED19 overexpression increases ELK1 occupancy at the MAOA promoter, and ELK1 depletion reduces MAOA expression and androgen-independent growth. This suggests that MED19 cooperates with ELK1 to regulate AR occupancy and H3K27 acetylation at MAOA, upregulating its expression and driving androgen independence in prostate cancer cells. This study provides important insight into the mechanisms of prostate cancer cell growth under low androgen, and underscores the importance of the MED19-MAOA axis in this process.

LMO2 upregulation due to AR deactivation in cancer-associated fibroblasts induces non-cell-autonomous growth of prostate cancer after androgen deprivation.

The androgen receptor (AR) is expressed in prostate fibroblasts in addition to normal prostate epithelial cells and prostate cancer (PCa) cells. Moreover, AR activation in fibroblasts dramatically influences prostate cancer (PCa) cell behavior. Androgen deprivation leads to deregulation of AR downstream target genes in both fibroblasts and PCa cells. Here, we identified LIM domain only 2 (LMO2) as an AR target gene in prostate fibroblasts using ChIP-seq and revealed that LMO2 can be repressed directly by AR through binding to androgen response elements (AREs), which results in LMO2 overexpression after AR deactivation due to normal prostate fibroblasts to cancer-associated fibroblasts (CAFs) transformation or androgen deprivation therapy. Next, we investigated the mechanisms of LMO2 overexpression in fibroblasts and the role of this event in non-cell-autonomous promotion of PCa cells growth in the androgen-independent manner through paracrine release of IL-11 and FGF-9. Collectively, our data suggest that AR deactivation deregulates LMO2 expression in prostate fibroblasts, which induces castration resistance in PCa cells non-cell-autonomously through IL-11 and FGF-9.

The androgen receptor is a tumor suppressor in estrogen receptor-positive breast cancer.

The role of the androgen receptor (AR) in estrogen receptor (ER)-α-positive breast cancer is controversial, constraining implementation of AR-directed therapies. Using a diverse, clinically relevant panel of cell-line and patient-derived models, we demonstrate that AR activation, not suppression, exerts potent antitumor activity in multiple disease contexts, including resistance to standard-of-care ER and CDK4/6 inhibitors. Notably, AR agonists combined with standard-of-care agents enhanced therapeutic responses. Mechanistically, agonist activation of AR altered the genomic distribution of ER and essential co-activators (p300, SRC-3), resulting in repression of ER-regulated cell cycle genes and upregulation of AR target genes, including known tumor suppressors. A gene signature of AR activity positively predicted disease survival in multiple clinical ER-positive breast cancer cohorts. These findings provide unambiguous evidence that AR has a tumor suppressor role in ER-positive breast cancer and support AR agonism as the optimal AR-directed treatment strategy, revealing a rational therapeutic opportunity.

PSA-Targeted Alpha-, Beta-, and Positron-Emitting Immunotheranostics in Murine Prostate Cancer Models and Nonhuman Primates.

Most patients with prostate cancer treated with androgen receptor (AR) signaling inhibitors develop therapeutic resistance due to restoration of AR functionality. Thus, there is a critical need for novel treatment approaches. Here we investigate the theranostic potential of hu5A10, a humanized mAb specifically targeting free PSA (KLK3). LNCaP-AR (LNCaP with overexpression of wildtype AR) xenografts (NSG mice) and KLK3_Hi-Myc transgenic mice were imaged with 89Zr- or treated with 90Y- or 225Ac-labeled hu5A10; biodistribution and subcellular localization were analyzed by gamma counting, PET, autoradiography, and microscopy. Therapeutic efficacy of [225Ac]hu5A10 and [90Y]hu5A10 in LNCaP-AR tumors was assessed by tumor volume measurements, time to nadir (TTN), time to progression (TTP), and survival. Pharmacokinetics of [89Zr]hu5A10 in nonhuman primates (NHP) were determined using PET. Biodistribution of radiolabeled hu5A10 constructs was comparable in different mouse models. Specific tumor uptake increased over time and correlated with PSA expression. Treatment with [90Y]/[225Ac]hu5A10 effectively reduced tumor burden and prolonged survival (P ≤ 0.0054). Effects of [90Y]hu5A10 were more immediate than [225Ac]hu5A10 (TTN, P < 0.0001) but less sustained (TTP, P < 0.0001). Complete responses were observed in 7 of 18 [225Ac]hu5A10 and 1 of 9 mice [90Y]hu5A10. Pharmacokinetics of [89Zr]hu5A10 were consistent between NHPs and comparable with those in mice. [89Zr]hu5A10-PET visualized the NHP-prostate over the 2-week observation period. We present a complete preclinical evaluation of radiolabeled hu5A10 in mouse prostate cancer models and NHPs, and establish hu5A10 as a new theranostic agent that allows highly specific and effective downstream targeting of AR in PSA-expressing tissue. Our data support the clinical translation of radiolabeled hu5A10 for treating prostate cancer.

WLS-Wnt signaling promotes neuroendocrine prostate cancer.

SummaryNeuroendocrine prostate cancer (NEPC) is a lethal prostate cancer subtype arising as a consequence of more potent androgen receptor (AR) targeting in castration-resistant prostate cancer (CRPC). Its molecular pathogenesis remains elusive. Here, we report that the Wnt secretion mediator Wntless (WLS) is a major driver of NEPC and aggressive tumor growth in vitro and in vivo. Mechanistic studies showed that WLS is a transcriptional target suppressed by AR that activates the ROR2/PKCδ/ERK signaling pathway to support the neuroendocrine (NE) traits and proliferative capacity of NEPC cells. Analysis of clinical samples and datasets revealed that WLS was highly expressed in CRPC and NEPC tumors. Finally, treatment with the Wnt secretion inhibitor LGK974 restricted NE prostate tumor xenograft growth in mice. These findings collectively characterize the contribution of WLS to NEPC pathogenesis and suggest that WLS is a potential therapeutic target in NEPC.

PRPF6 promotes androgen receptor/androgen receptor-variant 7 actions in castration-resistant prostate cancer cells.

Androgen receptor (AR) and its variants play vital roles in development and progression of prostate cancer. To clarify the mechanisms involved in the enhancement of their actions would be crucial for understanding the process in prostate cancer and castration-resistant prostate cancer transformation. Here, we provided the evidence to show that pre-mRNA processing factor 6 (PRPF6) acts as a key regulator for action of both AR full length (AR-FL) and AR variant 7 (AR-V7), thereby participating in the enhancement of AR-FL and AR-V7-induced transactivation in prostate cancer. In addition, PRPF6 is recruited to cis-regulatory elements in AR target genes and associates with JMJD1A to enhance AR-induced transactivation. PRPF6 also promotes expression of AR-FL and AR-V7. Moreover, PRPF6 depletion reduces tumor growth in prostate cancer-derived cell lines and results in significant suppression of xenograft tumors even under castration condition in mouse model. Furthermore, PRPF6 is obviously highly expressed in human prostate cancer samples. Collectively, our results suggest PRPF6 is involved in enhancement of oncogenic AR signaling, which support a previously unknown role of PRPF6 during progression of prostate cancer and castration-resistant prostate cancers.