Similar Datasets
Project description:Androgen receptor (AR) splice variants (ARVs) are implicated in developing castration-resistant (CR) prostate cancer (CRPC). Little is known about the ARV-mediated transcription program in CRPC. We identified ARV-preferred binding sites (ARV-PBS) and unique transcriptome in CRPC cells. ARVs preferentially bind to enhancers located in nucleosome-depleted regions with the full AR-response element (AREfull), while full-length AR (ARFL)-PBS are enhancers resided in closed chromatin regions with the composite FOXA1-nnnn-AREhalf motif. ARV-PBS exclusively overlapped with AR binding sites in CR patients. ARV-driven genes were up-regulated in abiraterone-resistant patient specimens and promote CRPC growth. We uncover distinct genomic and epigenomic characteristics of ARV-PBS and a unique ARV-dependent transcriptional program that not only drives CR progression but could also offer new targets for therapy. Increasing evidence suggests a pivotal role of ARVs in the acquisition of anti-AR therapy resistance in CRPC. It has been shown previously that ARVs possess unique structural and functional features such as completely lacking or only containing an impaired ligand-binding domain but constitutively active. Our findings advance the understanding of ARVs by demonstrating that ARV-PBS exhibit distinctive DNA-binding motif, GC content, and nucleosome and epigenetic characteristics. We further unravel that ARV-PBS exclusively overlap with AR bindings identified from castration-resistant patients and ARV activity is significantly increased in abiraterone-resistant patients. Given that there is no drug available to target ARVs at present, identification of ARV-mediated unique downstream pathways opens new avenues for the development of effective therapeutics for CRPC.
2018-03-07 | GSE80742 | GEO
Project description:Androgen receptor (AR) splice variants (ARVs) are implicated in developing castration-resistant (CR) prostate cancer (CRPC). Little is known about the ARV-mediated transcription program in CRPC. We identified ARV-preferred binding sites (ARV-PBS) and unique transcriptome in CRPC cells. ARVs preferentially bind to enhancers located in nucleosome-depleted regions with the full AR-response element (AREfull), while full-length AR (ARFL)-PBS are enhancers resided in closed chromatin regions with the composite FOXA1-nnnn-AREhalf motif. ARV-PBS exclusively overlapped with AR binding sites in CR patients. ARV-driven genes were up-regulated in abiraterone-resistant patient specimens and promote CRPC growth. We uncover distinct genomic and epigenomic characteristics of ARV-PBS and a unique ARV-dependent transcriptional program that not only drives CR progression but could also offer new targets for therapy. Increasing evidence suggests a pivotal role of ARVs in the acquisition of anti-AR therapy resistance in CRPC. It has been shown previously that ARVs possess unique structural and functional features such as completely lacking or only containing an impaired ligand-binding domain but constitutively active. Our findings advance the understanding of ARVs by demonstrating that ARV-PBS exhibit distinctive DNA-binding motif, GC content, and nucleosome and epigenetic characteristics. We further unravel that ARV-PBS exclusively overlap with AR bindings identified from castration-resistant patients and ARV activity is significantly increased in abiraterone-resistant patients. Given that there is no drug available to target ARVs at present, identification of ARV-mediated unique downstream pathways opens new avenues for the development of effective therapeutics for CRPC.
2018-03-07 | GSE80741 | GEO
Project description:Identification and characterization of androgen receptor splice variants preferred bindings that drive prostate cancer progression
| PRJNA319897 | ENA
Project description:Prostate cancer growth depends on androgen receptor signaling. Androgen ablation therapy induces expression of constitutively active androgen receptor splice variants that drive disease progression. Taxanes are a standard of care therapy in castration-resistant prostate cancer (CRPC); however, mechanisms underlying the clinical activity of taxanes are poorly understood. Recent work suggests that the microtubule network of prostate cells is critical for androgen receptor nuclear translocation and activity. In this study, we used a set of androgen receptor deletion mutants to identify the microtubule-binding domain of the androgen receptor, which encompasses the DNA binding domain plus hinge region. We report that two clinically relevant androgen receptor splice variants, ARv567 and ARv7, differentially associate with microtubules and dynein motor protein, thereby resulting in differential taxane sensitivity in vitro and in vivo. ARv7, which lacks the hinge region, did not co-sediment with microtubules or coprecipitate with dynein motor protein, unlike ARv567. Mechanistic investigations revealed that the nuclear accumulation and transcriptional activity of ARv7 was unaffected by taxane treatment. In contrast, the microtubule-interacting splice variant ARv567 was sensitive to taxane-induced microtubule stabilization. In ARv567-expressing LuCap86.2 tumor xenografts, docetaxel treatment was highly efficacious, whereas ARv7-expressing LuCap23.1 tumor xenografts displayed docetaxel resistance. Our results suggest that androgen receptor variants that accumulate in CRPC cells utilize distinct pathways of nuclear import that affect the antitumor efficacy of taxanes, suggesting a mechanistic rationale to customize treatments for patients with CRPC, which might improve outcomes.
| S-EPMC4012562 | biostudies-literature
Project description:Owing to the marked sexual dimorphism of hepatocellular carcinoma (HCC), sex hormone receptor signaling has been implicated in numerous aspects of liver cancer pathogenesis. We sought to reconcile the clear contribution of androgen receptor (AR) activity that has been established in preclinical models of HCC with the clinical failure of AR antagonists in patients with advanced HCC by evaluating potential resistance mechanisms to AR-targeted therapy. The AR locus was interrogated for resistance-causing genomic modifications using publicly available primary HCC datasets (1,019 samples). Analysis of HCC tumor and cell line RNA-seq data revealed enriched expression of constitutively active, treatment-refractory AR splice variants (AR-SV). HCC cell lines expressed C-terminal-truncated AR-SV; 28 primary HCC samples abundantly expressed AR-SV. Low molecular weight AR species were nuclear localized and constitutively active. Furthermore, AR/AR-SV signaling promoted AR-mediated HCC cell progression and conferred resistance to AR antagonists. Ligand-dependent and -independent AR signaling mediated HCC epithelial-to-mesenchymal transition by regulating the transcription factor SLUG. These data suggest that AR-SV expression in HCC drives HCC progression and resistance to traditional AR antagonists. Novel therapeutic approaches that successfully target AR-SVs may be therapeutically beneficial for HCC. SIGNIFICANCE: Treatment-refractory, constitutively active androgen receptor splice variants promote hepatocellular carcinoma progression by regulating the epithelial-to-mesenchymal transition pathway.
| S-EPMC7002251 | biostudies-literature
Project description:Mechanisms mediating androgen receptor (AR) reactivation in prostate cancer that progresses after castration (castration-resistant prostate cancer; CRPC) and subsequent treatment with abiraterone (CYP17A1 inhibitor that further suppresses androgen synthesis) remain unclear.Prostate cancer xenografts were examined to identify mechanism of progression after castration and abiraterone.AR reactivation in abiraterone-resistant VCaP xenografts was not associated with restoration of intratumoral androgens or alterations in AR coregulators. In contrast, mRNA encoding full-length AR (AR-FL) and a constitutively active splice variant (AR-V7) were increased compared with xenografts before castration, with an increase in AR-V7 relative to AR-FL. This shift toward AR-V7 was due to a feedback mechanism whereby the androgen-liganded AR stimulates expression of proteins that suppress generation of AR-V7 relative to AR-FL transcripts. However, despite the increases in AR-V7 mRNA, it remained a minor transcript (<1%) relative to AR-FL in resistant VCaP xenografts and CRPC clinical samples. AR-V7 protein expression was similarly low relative to AR-FL in castration-resistant VCaP xenografts and androgen-deprived VCaP cells, but the weak basal AR activity in these latter cells was further repressed by AR-V7 siRNA.AR-V7 at these low levels is not adequate to restore AR activity, but its rapid induction after androgen deprivation allows tumors to retain basal AR activity that may be needed for survival until more potent mechanisms emerge to activate AR. Agents targeting AR splice variants may be most effective when used very early in conjunction with therapies targeting the AR ligand-binding domain.
| S-EPMC4022291 | biostudies-literature
Project description:Therapeutic interventions for advanced prostate cancer (PCa) center on inhibiting androgen receptor (AR) and downstream signaling pathways. Resistance to androgen deprivation therapy and/or AR antagonists is inevitable and molecular mechanisms driving castration-resistant PCa (CR-PCa) primarily involve alterations in AR expression and activity. Detailed molecular biology work over the past decade, discussed at length in this review article, has revealed several AR transcripts that result from alternative splicing. These AR splice variants are increased in cell and mouse models of CR-PCa and in CR-PCa tumors. Several AR variants lack the ligand binding domain, but retain their ability to bind DNA and activate transcription-linking constitutive AR function and therapeutic failure. ARV7 is the only variant endogenously detected at the protein level and thus has undergone more thorough molecular characterization. Clinical trials in PCa are currently investigating ARV7 utility as a biomarker and new therapeutics that inhibit ARV7 . Overall, this review will illustrate the historical perspectives of AR splice variant discovery using fundamental molecular biology techniques and how it changed the clinical approach to both therapeutic decisions and strategy. The body of work investigating AR splice variants in PCa represents a true example of translational research from bench to bedside.
| S-EPMC5392349 | biostudies-literature
Project description:Androgen receptor (AR) splice variants lacking the ligand binding domain (ARVs), originally isolated from prostate cancer cell lines derived from a single patient, are detected in normal and malignant human prostate tissue, with the highest levels observed in late stage, castration-resistant prostate cancer. The most studied variant (called AR-V7 or AR3) activates AR reporter genes in the absence of ligand and therefore, could play a role in castration resistance. To explore the range of potential ARVs, we screened additional human and murine prostate cancer models using conventional and next generation sequencing technologies and detected several structurally diverse AR isoforms. Some, like AR-V7/AR3, display gain of function, whereas others have dominant interfering activity. We also find that ARV expression increases acutely in response to androgen withdrawal, is suppressed by testosterone, and in some models, is coupled to full-length AR (AR-FL) mRNA production. As expected, constitutively active, ligand-independent ARVs such as AR-V7/AR3 are sufficient to confer anchorage-independent (in vitro) and castration-resistant (in vivo) growth. Surprisingly, this growth is blocked by ligand binding domain-targeted antiandrogens, such as MDV3100, or by selective siRNA silencing of AR-FL, indicating that the growth-promoting effects of ARVs are mediated through AR-FL. These data indicate that the increase in ARV expression in castrate-resistant prostate cancer is an acute response to castration rather than clonal expansion of castration or antiandrogen-resistant cells expressing gain of function ARVs, and furthermore, they provide a strategy to overcome ARV function in the clinic.
| S-EPMC2947883 | biostudies-other
Project description:Resistance to the latest advanced prostate cancer therapies, including abiraterone and enzalutamide, is associated with increased expression of constitutively active androgen receptor splice variants (AR-Vs). The exact mechanism by which these therapies result in AR-Vs is unknown, but may include genomic rearrangement of the androgen receptor gene as well as alternative splicing of the AR pre-messenger RNA (mRNA). An additional complication that hinders further development of effective AR strategies is that the mechanisms by which the directed therapies are bypassed may vary. Finally, the question must be addressed as to whether the androgen receptor remains to be the driver of most castration resistant disease or whether truly AR-independent tumors arise after successful androgen ablation therapy. In this review, we will examine androgen receptor splice variants as an alternative mechanism by which prostate cancer becomes resistant to androgen receptor-directed therapy.
| S-EPMC4308035 | biostudies-literature
Project description:In 2015, as part of the Prostate Cancer Foundation-Movember Foundation Reproducibility Initiative, we published a Registered Report (Shan et al., 2015) that described how we intended to replicate selected experiments from the paper "Androgen Receptor Splice Variants Determine Taxane Sensitivity in Prostate Cancer" (Thadani-Mulero et al., 2014). Here we report the results of those experiments. Growth of tumor xenografts from two prostate cancer xenograft lines, LuCaP 86.2, which expresses wild-type androgen receptor (AR) and AR variant 567, and LuCaP 23.1, which expresses wild-type AR and AR variant 7, were not affected by docetaxel treatment. The LuCaP 23.1 tumor xenografts grew slower than in the original study. This result is different from the original study, which reported significant reduction of tumor growth in the LuCaP 86.2. Furthermore, we were unable to detect ARv7 in the LuCaP 23.1, although we used the antibody as stated in the original study and ensured that it was detecting ARv7 via a known positive control (22rv1, Hörnberg et al., 2011). Finally, we report a meta-analysis of the result.
| S-EPMC5907780 | biostudies-literature