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Second-Generation HSP90 Inhibitor Onalespib Blocks mRNA Splicing of Androgen Receptor Variant 7 in Prostate Cancer Cells.

ABSTRACT: Resistance to available hormone therapies in prostate cancer has been associated with alternative splicing of androgen receptor (AR) and specifically, the expression of truncated and constitutively active AR variant 7 (AR-V7). The transcriptional activity of steroid receptors, including AR, is dependent on interactions with the HSP90 chaperone machinery, but it is unclear whether HSP90 modulates the activity or expression of AR variants. Here, we investigated the effects of HSP90 inhibition on AR-V7 in prostate cancer cell lines endogenously expressing this variant. We demonstrate that AR-V7 and full-length AR (AR-FL) were depleted upon inhibition of HSP90. However, the mechanisms underlying AR-V7 depletion differed from those for AR-FL. Whereas HSP90 inhibition destabilized AR-FL and induced its proteasomal degradation, AR-V7 protein exhibited higher stability than AR-FL and did not require HSP90 chaperone activity. Instead, HSP90 inhibition resulted in the reduction of AR-V7 mRNA levels but did not affect total AR transcript levels, indicating that HSP90 inhibition disrupted AR-V7 splicing. Bioinformatic analyses of transcriptome-wide RNA sequencing data confirmed that the second-generation HSP90 inhibitor onalespib altered the splicing of at least 557 genes in prostate cancer cells, including AR. These findings indicate that the effects of HSP90 inhibition on mRNA splicing may prove beneficial in prostate cancers expressing AR-V7, supporting further clinical investigation of HSP90 inhibitors in malignancies no longer responsive to androgen deprivation. Cancer Res; 76(9); 2731-42. ©2016 AACR.

SUBMITTER: Ferraldeschi R

PROVIDER: S-EPMC4874658 | biostudies-other | 2016 May

REPOSITORIES: biostudies-other

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Second-Generation HSP90 Inhibitor Onalespib Blocks mRNA Splicing of Androgen Receptor Variant 7 in Prostate Cancer Cells.

Ferraldeschi Roberta R Welti Jonathan J Powers Marissa V MV Yuan Wei W Smyth Tomoko T Seed George G Riisnaes Ruth R Hedayat Somaieh S Wang Hannah H Crespo Mateus M Nava Rodrigues Daniel D Figueiredo Ines I Miranda Susana S Carreira Suzanne S Lyons John F JF Sharp Swee S Plymate Stephen R SR Attard Gerhardt G Wallis Nicola N Workman Paul P de Bono Johann S JS

Cancer research 20160501 9

Resistance to available hormone therapies in prostate cancer has been associated with alternative splicing of androgen receptor (AR) and specifically, the expression of truncated and constitutively active AR variant 7 (AR-V7). The transcriptional activity of steroid receptors, including AR, is dependent on interactions with the HSP90 chaperone machinery, but it is unclear whether HSP90 modulates the activity or expression of AR variants. Here, we investigated the effects of HSP90 inhibition on A ...[more]

PMID: 27197266

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Project description:BackgroundNonmetastatic castration-resistant prostate cancer (nmCRPC) is defined as a rising prostate-specific antigen concentration, despite castrate levels of testosterone with ongoing androgen-deprivation therapy or orchiectomy, and no detectable metastases by conventional imaging. Patients with nmCRPC progress to metastatic disease and are at risk of developing cancer-related symptoms and morbidity, eventually dying of their disease. While patients with nmCRPC are generally asymptomatic from their disease, they are often older and have chronic comorbidities that require long-term concomitant medication. Therefore, careful consideration of the benefit-risk profile of potential treatments is required.MethodsIn this review, we will discuss the rationale for early treatment of patients with nmCRPC to delay metastatic progression and prolong survival, as well as the factors influencing this treatment decision. We will focus on oral pharmacotherapy with the second-generation androgen receptor inhibitors, apalutamide, enzalutamide, and darolutamide, and the importance of balancing the clinical benefit they offer with potential adverse events and the consequential impact on quality of life, physical capacity, and cognitive function.Results and conclusionsWhile the definition of nmCRPC is well established, the advent of next-generation imaging techniques capable of detecting hitherto undetectable oligometastatic disease in patients with nmCRPC has fostered debate on the criteria that inform the management of these patients. However, despite these developments, published consensus statements have maintained that the absence of metastases on conventional imaging suffices to guide such therapeutic decisions. In addition, the prolonged metastasis-free survival and recently reported positive overall survival outcomes of the three second-generation androgen receptor inhibitors have provided further evidence for the early use of these agents in patients with nmCRPC in order to delay metastases and prolong survival. Here, we discuss the benefit-risk profiles of apalutamide, enzalutamide, and darolutamide based on the data available from their pivotal clinical trials in patients with nmCRPC.

Dataset Information

Second-Generation HSP90 Inhibitor Onalespib Blocks mRNA Splicing of Androgen Receptor Variant 7 in Prostate Cancer Cells.

Publications

Second-Generation HSP90 Inhibitor Onalespib Blocks mRNA Splicing of Androgen Receptor Variant 7 in Prostate Cancer Cells.

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