Androgen Receptor Coactivator Research Articles

Abstract B012: Histone demethylase JMJD1A promotes the generation of androgen receptor variant 7 (AR-V7) in prostate cancer cells

Abstract Generation of androgen receptor (AR) splicing variant, AR-V7, has been shown to contribute to the resistance of prostate cancer to androgen deprivation therapy and development of castration-resistant prostate cancer (CRPC). We and others have reported that histone demethylase JMJD1A promotes the transcriptional activity of AR by functioning as an AR coactivator. Here, we identified a new role for JMJD1A in the generation of AR-V7 in prostate cancer cells through interaction with HNRFPF. Knockdown of JMJD1A or HNRNPF reduced the mRNA and protein level of AR-V7 but had little effect on the full-length AR (AR-FL). Mechanistically, we found that JMJD1A and HNRNPF cooperatively bound to a polyG motif adjacent to the 5′ splicing site of Exon3b of AR gene, where they promoted the assembly of splicesome. Re-expression of AR-V7 in the JMJD1A-knockdown cells partly rescued the growth defect of prostate cancer cells in vitro and in the mouse xenograft model. The staining of AR-V7 paralleled that of JMJD1A or HNRNFP in a human prostate cancer tissue microarray. Together, our data reveal that JMJD1A enhances the castration-resistant growth of prostate cancer cells through coactivation of AR-FL and generation of AR-V7. Citation Format: Lingling Fan, Fengbo Zhang, Ladan Fazli, Martin Gleave, Xuesen Dong, Jianfei Qi. Histone demethylase JMJD1A promotes the generation of androgen receptor variant 7 (AR-V7) in prostate cancer cells [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B012.

KDM8/JMJD5 as a dual coactivator of AR and PKM2 integrates AR/EZH2 network and tumor metabolism in CRPC

During the evolution into castration or therapy resistance, prostate cancer cells reprogram the androgen responses to cope with the diminishing level of androgens, and undergo metabolic adaption to the nutritionally deprived and hypoxia conditions. AR (androgen receptor) and PKM2 (pyruvate kinase M2) have key roles in these processes. We report in this study, KDM8/JMJD5, a histone lysine demethylase/dioxygnase, exhibits a novel property as a dual coactivator of AR and PKM2 and as such, it is a potent inducer of castration and therapy resistance. Previously, we showed that KDM8 is involved in the regulation of cell cycle and tumor metabolism in breast cancer cells. Its role in prostate cancer has not been explored. Here, we show that KDM8’s oncogenic properties in prostate cancer come from its direct interaction (1) with AR to affect androgen response and (2) with PKM2 to regulate tumor metabolism. The interaction with AR leads to the elevated expression of androgen response genes in androgen-deprived conditions. They include ANCCA/ATAD2 and EZH2, which are directly targeted by KDM8 and involved in sustaining the survival of the cells under hormone-deprived conditions. Notably, in enzalutamide-resistant cells, the expressions of both KDM8 and EZH2 are further elevated, so are neuroendocrine markers. Consequently, EZH2 inhibitors or KDM8 knockdown both resensitize the cells toward enzalutamide. In the cytosol, KDM8 associates with PKM2, the gatekeeper of pyruvate flux and translocates PKM2 into the nucleus, where the KDM8/PKM2 complex serves as a coactivator of HIF-1α to upregulate glycolytic genes. Using shRNA knockdown, we validate KDM8’s functions as a regulator for both androgen-responsive and metabolic genes. KDM8 thus presents itself as an ideal therapeutic target for metabolic adaptation and castration-resistance of prostate cancer cells.

High-Content Screening Campaign to Identify Compounds That Inhibit or Disrupt Androgen Receptor-Transcriptional Intermediary Factor 2 Protein-Protein Interactions for the Treatment of Prostate Cancer.

Twenty percent of prostate cancer (PCa) patients develop a noncurable drug-resistant form of the disease termed castration-resistant prostate cancer (CRPC). Overexpression of Androgen Receptor (AR) coactivators such as transcriptional intermediary factor 2 (TIF2) is associated with poor CRPC patient outcomes. We describe the implementation of the AR-TIF2 protein-protein interaction biosensor (PPIB) assay in a high-content screening (HCS) campaign of 143,535 compounds. The assay performed robustly and reproducibly and enabled us to identify compounds that inhibited dihydrotestosterone (DHT)-induced AR-TIF2 protein-protein interaction (PPI) formation or disrupted preexisting AR-TIF2 PPIs. We used multiparameter HCS data z-scores to identify and deprioritize cytotoxic or autofluorescent outliers and confirmed the resulting qualified actives in triplicate. None of the confirmed AR-TIF2 PPIB inhibitors/disruptors exhibited activity in a p53-hDM2 PPIB counter screen, indicating that they were unlikely to be either nonselective PPI inhibitors or to interfere with the biosensor assay format. However, eight confirmed AR-TIF2 PPIB actives also inhibited the glucocorticoid receptor (GR) nuclear translocation counter screen by >50%. These compounds were deprioritized because they either lacked AR specificity/selectivity, or they inhibited a shared component of the AR and GR signaling pathways. Twenty-nine confirmed AR-TIF2 PPIB actives also inhibited the AR nuclear localization counter screen, suggesting that they might indirectly inhibit the AR-TIF2 PPIB assay rather than directly blocking/disrupting PPIs. A total of 62.2% of the confirmed actives inhibited the DHT-induced AR-TIF2 PPI formation in a concentration-dependent manner with IC50s < 40 μM, and 59.4% also disrupted preexisting AR-TIF2 PPI complexes. Overall, the hit rate for the AR-TIF2 PPIB HCS campaign was 0.12%, and most hits inhibited AR-TIF2 PPI formation and disrupted preexisting AR-TIF2 complexes with similar AR-red fluorescent protein distribution phenotypes. Further secondary and tertiary hit characterization assays are underway to select AR-TIF2 PPI inhibitor/disruptor hits suitable for medicinal chemistry lead optimization and development into novel PCa/CRPC therapeutics.

LSD1 inhibition attenuates androgen receptor V7 splice variant activation in castration resistant prostate cancer models

BackgroundCastrate resistant prostate cancer (CRPC) is often driven by constitutively active forms of the androgen receptor such as the V7 splice variant (AR-V7) and commonly becomes resistant to established hormonal therapy strategies such as enzalutamide as a result. The lysine demethylase LSD1 is a co-activator of the wild type androgen receptor and a potential therapeutic target in hormone sensitive prostate cancer. We evaluated whether LSD1 could also be therapeutically targeted in CRPC models driven by AR-V7.MethodsWe utilised cell line models of castrate resistant prostate cancer through over expression of AR-V7 to test the impact of chemical LSD1 inhibition on AR activation. We validated findings through depletion of LSD1 expression and in prostate cancer cell lines that express AR-V7.ResultsChemical inhibition of LSD1 resulted in reduced activation of the androgen receptor through both the wild type and its AR-V7 splice variant forms. This was confirmed and validated in luciferase reporter assays, in LNCaP and 22Rv1 prostate cancer cell lines and in LSD1 depletion experiments.ConclusionLSD1 contributes to activation of both the wild type and V7 splice variant forms of the androgen receptor and can be therapeutically targeted in models of CRPC. Further development of this approach is warranted.

Recent advances on the progressive mechanism and therapy in castration-resistant prostate cancer.

BackgroundAlthough there have been great advances in mechanisms and therapeutic methods of prostate cancer, the mortality rate of prostate cancer remains high. The castration-resistant prostate cancer (CRPC), which develops from hormone-sensitive prostate cancer, foreshadows a more dismal outcome. Concomitant with the researches in the mechanism of CRPC and therapy for CRPC, more and more landmark progress has been made in recent years.MethodsA number of clinical and experimental studies were reviewed to indicate the novel advancement in the progressive mechanism and therapy of CRPC.ResultsThe androgen receptor (AR) is still a vital driver in the progression of CRPC, while other multiple mechanisms also contribute to this progression, such as tumor immunity, cancer stem cells, epithelial–mesenchymal transition and DNA repair disorder. In terms of the therapeutic methods of CRPC, chemotherapy with drugs, such as docetaxel, has been the first-line therapy for CRPC for many years. Besides, newer agents, which target some of the above mechanisms, show additional overall survival benefits for CRPC patients. These therapies include drugs targeting the androgen axis pathway (androgen synthesis, androgen receptor splice variants, coactivators of AR and so on), PI3K-AKT pathway, WNT pathway, DNA repair, rearrangement of ETS gene, novel chemotherapy and immunotherapy, bone metastasis therapy and so on. Understanding these novel findings on the mechanisms of CRPC and the latest potential CRPC therapies will direct us for further exploration of CRPC.ConclusionThrough comprehensive consideration, the predominant mechanism of CRPC might be the AR signal axis concomitant with tumor microenvironment, stress, immunity, tumor microenvironment and so on. For CRPC therapy, targeting the AR axis pathway and chemotherapy are the first-line treatments at present. However, with the advancements in CRPC therapy made by the researchers, other novel potential methods will occupy more and more important position in the treatment of CRPC, especially the therapies targeting the tumor microenviroment, tumor immunity and DNA repair and so on.

Androgen receptor‑mediated upregulation of quaking affects androgen receptor‑related prostate cancer development and anti‑androgen receptor therapy.

The androgen receptor (AR) has a crucial role in prostate cancer. RNA-binding protein-mediated post-transcriptional regulation is important in the initiation and development of cancer. The present study attempted to elucidate the mutual association of AR and RNA-binding protein quaking (QKI) in the development of prostate cancer. Dual-luciferase reporter demonstrated that AR can positively regulate the expression of QKI in prostate cancer cell lines due to its effective transcription regulating function. In addition, QKI may increase expression of AR by heat shock protein 90, which is a coactivator of AR, and silencing QKI can increase the sensitive of Casodex, which is an antagonist of AR in castration-resistant prostate cancer. This may be a new strategy for advanced prostate cancer.

Corni Fructus attenuates testosterone-induced benign prostatic hyperplasia by suppressing 5α-reductase and androgen receptor expression in rats.

BACKGROUND/OBJECTIVESBenign prostatic hypertrophy (BPH) is a major cause of abnormal overgrowth of the prostate mainly in the elderly. Corni Fructus has been reported to be effective in the prevention and treatment of various diseases because of its strong antioxidant effect, but its efficacy against BPH is not yet known. This study was designed to evaluate the therapeutic efficacy of Corni Fructus water extract (CF) in testosterone-induced BPH rats.MATERIALS/METHODSTo induce BPH, rats were intraperitoneal injected with testosterone propionate (TP). Rats in the treatment group were orally administered with CF with TP injection, and finasteride, which is a selective inhibitor of 5α-reductase type 2, was used as a positive control.RESULTSOur results showed that the increased prostate weight and histopathological changes in BPH model rats were suppressed by CF treatment. CF, similar to the finasteride-treated group, decreased the levels of testosterone and dihydrotestosterone by TP treatment in the serum, and it also reduced 5α-reductase expression and concentration in prostate tissue and serum, respectively. In addition, CF significantly blocked the expression of the androgen receptor (AR), AR co-activators, and proliferating cell nuclear antigen in BPH rats, and this blocking was associated with a decrease in prostate-specific antigen levels in serum and prostate tissue.CONCLUSIONSThese results suggest that CF may weaken the BPH status through the inactivation of at least 5α-reductase and AR activity and may be useful for the clinical treatment of BPH.

Oncogenic non-coding RNA NEAT1 promotes the prostate cancer cell growth through the SRC3/IGF1R/AKT pathway.

Steroid receptor co-activator3 (SRC3) has been known to severe as an androgen receptor (AR) coactivator and is involved in the prostate cancer progression. Non-coding RNA (ncRNA) plays an important role in the cancer progression. However, the mechanism underlying the relationship between ncRNA and AR coactivators is still unclear. Here, we found a ncRNA, Nuclear Enriched Abundant Transcript 1 (NEAT1), was able to interact with SRC3 in the prostate cancer cell lines. NEAT1 can upregulate the AKT phosphorylation via a SRC3/IGF1R pathway. In function, NEAT1 promoted the prostate cancer cell growth through IGF1R/AKT signaling pathway. The NEAT1, SRC3, and IGF1R were highly expressed in the patients' samples of prostate cancer. Therefore, we found a novel SRC3 binding ncRNA that can promote the prostate cancer cell growth through SRC3/IGF1R/AKT pathway.

The interaction between androgen receptor and semenogelin I: a synthetic LxxLL peptide antagonist inhibits the growth of prostate cancer cells

Background:We previously demonstrated that a seminal plasma protein, semenogelin I (SgI), functioned as an androgen receptor (AR) coactivator. Meanwhile, several short sequence motifs in AR coregulators, such as LxxLL (L=leucine), have been shown to mediate specific interactions with AR.Methods:We investigated the role of the LxxLL motif within SgI in the interactions with AR and cell growth in prostate cancer lines in vitro.Results:A full-length SgI with mutations in the motif (i.e., LxxAA; A=alanine) failed to significantly increase cell proliferation/migration as well as androgen-mediated AR transcription. Co-immunoprecipitation showed no physical interactions between AR and the mutant SgI. In addition, transfection of an 18-amino acid peptide of SgI containing LxxLL, but not LxxAA, resulted in considerable reduction in cell growth and prostate-specific antigen expression in LNCaP and C4-2 lines.Conclusions:The LxxLL motif of SgI could be a novel therapeutic target for both androgen-sensitive and castration-resistant prostate cancers.

High Content Positional Biosensor Assay to Screen for Compounds that Prevent or Disrupt Androgen Receptor and Transcription Intermediary Factor 2 Protein-Protein Interactions.

Transcriptional Intermediary Factor 2 (TIF2) is a key Androgen receptor (AR) coactivator that has been implicated in the development and progression of castration resistant prostate cancer (CRPC). This chapter describes the implementation of an AR-TIF2 protein-protein interaction (PPI) biosensor assay to screen for small molecules that can induce AR-TIF2 PPIs, inhibit the DHT-induced formation of AR-TIF2 PPIs, or disrupt pre-existing AR-TIF2 PPIs. The biosensor assay employs high content imaging and analysis to quantify AR-TIF2 PPIs and integrates physiologically relevant cell-based assays with the specificity of binding assays by incorporating structural information from AR and TIF2 functional domains along with intracellular targeting sequences using fluorescent protein reporters. Expression of the AR-Red Fluorescent Protein (RFP) "prey" and TIF2-Green Fluorescent Protein (GFP) "bait" components of the biosensor is directed by recombinant adenovirus (rAV) expression constructs that facilitated a simple co-infection protocol to produce homogeneous expression of both biosensors that is scalable for screening. In untreated cells, AR-RFP expression is localized predominantly to the cytoplasm and TIF2-GFP expression is localized only in the nucleoli of the nucleus. Exposure to DHT induces the co-localization of AR-RFP within the TIF2-GFP positive nucleoli of the nucleus. The AR-TIF2 biosensor assay therefore recapitulates the ligand-induced translocation of latent AR from the cytoplasm to the nucleus, and the PPIs between AR and TIF2 result in the colocalization of AR-RFP within TIF2-GFP expressing nucleoli. The AR-TIF2 PPI biosensor approach offers significant promise for identifying molecules with potential to modulate AR transcriptional activity in a cell-specific manner that may overcome the development of resistance and progression to CRPC.

DHX15 promotes prostate cancer progression by stimulating Siah2-mediated ubiquitination of androgen receptor.

Androgen receptor (AR) activation is critical for prostate cancer development and progression, including castration-resistance. The nuclear export signal of AR (NESAR) plays an important role in AR intracellular trafficking and proteasome-dependent degradation. Here, we identified the RNA helicase DHX15 as a novel AR co-activator using a yeast mutagenesis screen and revealed that DHX15 regulates AR activity by modulating E3 ligase Siah2-mediated AR ubiquitination independent of its ATPase activity. DHX15 and Siah2 form a complex with AR, through NESAR. DHX15 stabilized Siah2 and enhanced its E3 ubiquitin ligase activity, resulting in AR activation. Importantly, DHX15 was upregulated in prostate cancer specimens and its expression was correlated with Gleason scores and PSA recurrence. Furthermore, DHX15 immunostaining correlated with Siah2. Finally, DHX15 knockdown inhibited the growth of C4-2 prostate tumor xenografts in mice. Collectively, our data argue that DHX15 enhances AR transcriptional activity and contributes to prostate cancer progression through Siah2.

Abstract LB-088: Role of histone demethylase JMJD1A in the generation of AR-V7

Abstract Formation of androgen receptor (AR) splicing variant, AR-V7, has been shown to contribute to the resistance of prostate cancer to androgen deprivation therapy and development of castration-resistant prostate cancer (CRPC). We and others have reported that histone demethylase JMJD1A promotes the transcriptional activity of AR by functioning as an AR co-activator. Here, we identified a new role for JMJD1A in the expression of AR-V7 in prostate cancer cells. Knockdown of JMJD1A reduced the mRNA and protein level of AR-V7 but had little effect on the full-length AR (AR-FL). Re-expression of AR-V7 in the JMJD1A-knockdown cells partly restored the expression of select AR target genes and growth of prostate cancer cells under the androgen deprivation condition in vitro and in the mouse xenograft model. Our preliminary data show that JMJD1A promotes the alternative splicing of AR-V7 and we are currently investigating the splicing factor(s) regulated by JMJD1A for the AR-V7 formation. Together, our data reveal that JMJD1A enhances the castration-resistant growth of prostate cancer cells by promoting the alternative splicing of AR-V7. Note: This abstract was not presented at the meeting. Citation Format: Lingling Fan, Fengbo Zhang, Martin Gleave, Xuesen Dong, Jianfei Qi. Role of histone demethylase JMJD1A in the generation of AR-V7 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-088. doi:10.1158/1538-7445.AM2017-LB-088

Abstract 1444: Validation of prostate cancer risk variants by CRISPR/Cas9 mediated genome editing at the MSMB locus

Abstract Genome wide association studies (GWAS) have identified nuermous single nucleotide polymorphisms (SNPs) associated with prostate cancer risk. While numerous in silico analyses suggest that the majority of these SNPs may function through regulation of gene expression, wet lab experiments to distinguish the causative variants from their linkage disequilibrium (LD) partners is still needed. Here, we demonstrate how genome editing can investigate the role of individual polymorphisms on gene expression. Here, we focus on the prostate cancer-associated SNP rs10993994, which is in the promoter of the MSMB gene that encodes for the prostate-secreted protein beta-MSP. This SNP is notable because it associates with seminal and serum levels of beta-MSP, PSA, and hK2; mRNA levels of MSMB and the nearby androgen receptor co-activator NCOA4 in the prostate; and mRNA levels of MSMB in the stomach. Intriguingly, rs10993994 is not a gastric cancer risk SNP suggesting that there may be other variants with prostate-specific function responsible for the observed prostate cancer association. Using data from the FANTOM5 project, we show that rs7098889, in LD with rs10993994, is located in one of the most prostate-specific enhancers. We had previously shown that this SNP is associated with beta-MSP independent of rs10993994. To distinguish the effects of these two SNPs on gene expression, we generated a series of double gRNA mediated CRISPR/Cas9 deletions of the relevant regulatory elements. Removing the element containing rs7098889 flanking region results in ~10 to 20 fold increase of MSMB expression in the prostate cancer LNCaP cell line but not in the gastric cancer AGS cell line. There is no change in NCOA4 in either cell line. Removing rs10993994 flanking region results in over 10 fold increase of MSMB expression and ~50% decrease of NCOA4 in LNCaP. As both LNCaP and AGS are heterozygous for both SNPs, we then generated single clones in which only one allele was removed. For rs7098889, an over 300 fold increase of MSMB expression was observed in two out of the three clones with the T but not the C allele. Transcripts from high expressers all came from one allele. Similarly, single clone analysis showed 40 to 60 fold up-regulation of MSMB expression in two out of three clones with the C but not the T allele of rs10993994. This is consistent with the observation for rs7098889 since rs7098889T and rs10993994C are on the same haplotype. Our work demonstrates dramatic and locus specific effect of individual polymorphisms on gene expression, which strongly support the notion that an important function of disease risk variants is through regulation of gene expression. Citation Format: Xing Wang, James Hayes, Xing Xu, Dipti Mehtad, Xiaoni Gao, Hans Lilja, Robert Klein. Validation of prostate cancer risk variants by CRISPR/Cas9 mediated genome editing at the MSMB locus [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1444. doi:10.1158/1538-7445.AM2017-1444

Abstract 3326: Identification of a novel androgen receptor co-regulator in prostate cancer

Abstract Prostate cancer (PC) is one of the most frequently diagnosed tumors in the United States, affecting one in six men during their lifetime and second only to lung cancer as a cause of cancer death in men. One of the major drivers of prostate cancer is the androgen receptor (AR). It has been shown that deregulation of AR co-regulators play a crucial role in PC through modulating the transcriptional activity of the receptor. While the importance of the AR complex is well established, there is still an incomplete understanding of what all the associated co-regulators are and how they modulate AR signaling. Here, we have identified that the inhibitor of growth family member 4 (ING4), a protein that has been implicated in the pathogenesis of several solid tumors such as gastric and breast cancer, is a novel AR co-regulator. Overexpression of ING4 increased AR activity in an androgen-dependent manner as assessed using luciferase reporter gene assays. Supporting a role as a potential AR co-activator, RNA Next-Generation Sequencing of prostate cancer cells with ING4 knocked down revealed a repression of endogenous AR/R1881-activated genes and expression of AR/R1881 suppressed genes. Further, mining of existing clinical datasets revealed that the ING4 gene expression is de-regulated in PCs compared relative to normal tissue and tracks with poor patient prognosis. Collectively, the current findings strongly support the involvement of ING4 in AR signaling and PC progression and development. Citation Format: Aymen A. Shatnawi, Sridhar Acharya Malkaram, Efrosini Tsouko, Daniel E. Frigo. Identification of a novel androgen receptor co-regulator in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3326. doi:10.1158/1538-7445.AM2017-3326

Functional interaction between co-expressed MAGE-A proteins.

MAGE-A (Melanoma Antigen Genes-A) are tumor-associated proteins with expression in a broad spectrum of human tumors and normal germ cells. MAGE-A gene expression and function are being increasingly investigated to better understand the mechanisms by which MAGE proteins collaborate in tumorigenesis and whether their detection could be useful for disease prognosis purposes. Alterations in epigenetic mechanisms involved in MAGE gene silencing cause their frequent co-expression in tumor cells. Here, we have analyzed the effect of MAGE-A gene co-expression and our results suggest that MageA6 can potentiate the androgen receptor (AR) co-activation function of MageA11. Database search confirmed that MageA11 and MageA6 are co-expressed in human prostate cancer samples. We demonstrate that MageA6 and MageA11 form a protein complex resulting in the stabilization of MageA11 and consequently the enhancement of AR activity. The mechanism involves association of the Mage A6-MHD domain to MageA11, prevention of MageA11 ubiquitinylation on lysines 240 and 245 and decreased proteasome-dependent degradation. We experimentally demonstrate here for the first time that two MAGE-A proteins can act together in a non-redundant way to potentiate a specific oncogenic function. Overall, our results highlight the complexity of the MAGE gene networking in regulating cancer cell behavior.

ING3 promotes prostate cancer growth by activating the androgen receptor

BackgroundThe androgen receptor (AR) is a major driver of prostate cancer, and increased AR levels and co-activators of the receptor promote the development of prostate cancer. INhibitor of Growth (ING) proteins target lysine acetyltransferase or lysine deacetylase complexes to the histone H3K4Me3 mark of active transcription, to affect chromatin structure and gene expression. ING3 is a stoichiometric member of the TIP60 lysine acetyltransferase complex implicated in prostate cancer development.MethodsBiopsies of 265 patients with prostate cancer were stained for ING3, pan-cytokeratin, and DNA. LNCaP and C4-2 androgen-responsive cells were used for in vitro assays including immunoprecipitation, western blotting, Luciferase reporter assay and quantitative polymerase chain reaction. Cell viability and migration assays were performed in prostate cancer cell lines using scrambled siRNA or siRNA targeting ING3.ResultsWe find that ING3 levels and AR activity positively correlate in prostate cancer. ING3 potentiates androgen effects, increasing expression of androgen-regulated genes and androgen response element-driven reporters to promote growth and anchorage-independent growth. Conversely, ING3 knockdown inhibits prostate cancer cell growth and invasion. ING3 activates the AR by serving as a scaffold to increase interaction between TIP60 and the AR in the cytoplasm, enhancing receptor acetylation and translocation to the nucleus. Activation is independent of ING3's ability to target the TIP60 complex to H3K4Me3, identifying a previously unknown chromatin-independent cytoplasmic activity for ING3. In agreement with in vitro observations, analysis of The Cancer Genome Atlas (TCGA) data (n = 498) and a prostate cancer tissue microarray (n = 256) show that ING3 levels are higher in aggressive prostate cancers, with high levels of ING3 predicting shorter patient survival in a low AR subgroup. Including ING3 levels with currently used indicators such as the Gleason score provides more accurate prognosis in primary prostate cancer.ConclusionsIn contrast to the majority of previous reports suggesting tumor suppressive functions in other cancers, our observations identify a clear oncogenic role for ING3, which acts as a co-activator of AR in prostate cancer. Data from TCGA and our previous and current tissue microarrays suggest that ING3 levels correlate with AR levels and that in patients with low levels of the receptor, ING3 level could serve as a useful prognostic biomarker.

Androgen receptor-positive, triple-negative breast cancer.

Androgen receptor-positive, triple-negative breast cancer.

Identification of neuron selective androgen receptor inhibitors.

AIMTo identify neuron-selective androgen receptor (AR) signaling inhibitors, which could be useful in the treatment of spinal and bulbar muscular atrophy (SBMA), or Kennedy’s disease, a neuromuscular disorder in which deterioration of motor neurons leads to progressive muscle weakness.METHODSCell lines representing prostate, kidney, neuron, adipose, and muscle tissue were developed that stably expressed the CFP-AR-YFP FRET reporter. We used these cells to screen a library of small molecules for cell type-selective AR inhibitors. Secondary screening in luciferase assays was used to identify the best cell-type specific AR inhibitors. The mechanism of action of a neuron-selective AR inhibitor was examined in vitro using luciferase reporter assays, immunofluorescence microscopy, and immunoprecipitations. Rats were treated with the most potent compound and tissue-selective AR inhibition was examined using RT-qPCR of AR-regulated genes and immunohistochemistry.RESULTSWe identified the thiazole class of antibiotics as compounds able to inhibit AR signaling in a neuronal cell line but not a muscle cell line. One of these antibiotics, thiostrepton is able to inhibit the activity of both wild type and polyglutamine expanded AR in neuronal GT1-7 cells with nanomolar potency. The thiazole antibiotics are known to inhibit FOXM1 activity and accordingly, a novel FOXM1 inhibitor FDI-6 also inhibited AR activity in a neuron-selective fashion. The selective inhibition of AR is likely indirect as the varied structures of these compounds would not suggest that they are competitive antagonists. Indeed, we found that FOXM1 expression correlates with cell-type selectivity, FOXM1 co-localizes with AR in the nucleus, and that shRNA-mediated knock down of FOXM1 reduces AR activity and thiostrepton sensitivity in a neuronal cell line. Thiostrepton treatment reduces FOXM1 levels and the nuclear localization of beta-catenin, a known co-activator of both FOXM1 and AR, and reduces the association between beta-catenin and AR. Treatment of rats with thiostrepton demonstrated AR signaling inhibition in neurons, but not muscles.CONCLUSIONOur results suggest that thiazole antibiotics, or other inhibitors of the AR-FOXM1 axis, can inhibit AR signaling selectively in motor neurons and may be useful in the treatment or prevention of SBMA symptoms.

Androgen receptor regulation by histone methyltransferase Suppressor of variegation 3-9 homolog 2 and Melanoma antigen-A11

Androgen receptor (AR) transcriptional activity depends on interactions between the AR NH2-terminal region and transcriptional coregulators. A yeast two-hybrid screen of a human testis library using predicted α-helical NH2-terminal fragment AR-(370-420) as bait identified suppressor of variegation 3-9 homolog 2 (SUV39H2) histone methyltransferase as an AR interacting protein. SUV39H2 interaction with AR and the AR coregulator, melanoma antigen-A11 (MAGE-A11), was verified in two-hybrid, in vitro glutathione S-transferase affinity matrix and coimmunoprecipitation assays. Fluorescent immunocytochemistry colocalized SUV39H2 and AR in the cytoplasm without androgen, in the nucleus with androgen, and with MAGE-A11 in the nucleus independent of androgen. Chromatin immunoprecipitation using antibodies raised against SUV39H2 demonstrated androgen-dependent recruitment of AR and SUV39H2 to the androgen-responsive upstream enhancer of the prostate-specific antigen gene. SUV39H2 functioned cooperatively with MAGE-A11 to increase androgen-dependent AR transcriptional activity. SUV39H2 histone methyltransferase is an AR coactivator that increases androgen-dependent transcriptional activity through interactions with AR and MAGE-A11.

The HIF/PHF8/AR axis promotes prostate cancer progression.

Recent studies provide strong evidence that the androgen receptor (AR) signaling pathway remains active in castration-resistant prostate cancer (CRPC). However, the underlying mechanisms are not well understood. In this study, we demonstrate that plant homeo domain finger protein 8 (PHF8 )interacts with and functions as an essential histone demethylase activity-dependent AR coactivator. Furthermore, we demonstrate that the expression of PHF8 is induced by hypoxia in various prostate cancer cell lines. Knockdown of either hypoxia-inducible factor HIF2α or HIF1α almost completely abolished hypoxia-induced PHF8 expression. Importantly, we observed that PHF8 is highly expressed in clinical androgen deprived prostate cancer samples and expression of PHF8 correlates with increased levels of HIF1α and HIF2α. Moreover, elevated PHF8 is associated with higher grade prostate cancers and unfavorable outcomes. Our findings support a working model in which hypoxia in castrated prostate cancer activates HIF transcription factors which then induces PHF8 expression. The elevated PHF8 in turn promotes the AR signaling pathway and prostate cancer progression. Therefore, the HIF/PHF8/AR axis could serve as a potential biomarker for CRPC and is also a promising therapeutic target in combating CRPC.