Genetic testing practices among specialist physicians who treat prostate cancer A Canadian, cross-sectional survey.

INTRODUCTION: In patients with prostate cancer (PCa), the identification of an alteration in genes associated with homologous recombination repair (HRR) has implications for prognostication, optimization of therapy, and familial risk mitigation. The aim of this study was to assess the genomic testing landscape of PCa in Canada and to recommend an approach to offering germline and tumor testing for HRR-associated genes. METHODS: The Canadian Genitourinary Research Consortium (GURC) administered a cross-sectional survey to a largely academic, multidisciplinary group of investigators across 22 GURC sites between January and June 2022. RESULTS: Thirty-eight investigators from all 22 sites responded to the survey. Germline genetic testing was initiated by 34%, while 45% required a referral to a genetic specialist. Most investigators (82%) reported that both germline and tumor testing were needed, with 92% currently offering germline and 72% offering tissue testing to patients with advanced PCa. The most cited reasons for not offering testing were an access gap (50%), uncertainties around who to test and which genes to test, (33%) and interpreting results (17%). A majority reported that patients with advanced PCa (74-80%) should be tested, with few investigators testing patients with localized disease except when there is a family history of PCa (45-55%). CONCLUSIONS: Canadian physicians with academic subspecialist backgrounds in genitourinary malignancies recognize the benefits of both germline and somatic testing in PCa; however, there are challenges in accessing testing across practices and specialties. An algorithm to reduce uncertainty for providers when ordering genetic testing for patients with PCa is proposed.

Patterns of care for non-metastatic castration-resistant prostate cancer: A population-based study.

Objectives: To describe patterns of practice of PSA testing and imaging for Ontario men receiving continuous ADT for the treatment of non-metastatic castration-resistant prostate cancer (nmCRPC). Patients and Methods: This was a retrospective, longitudinal, population-based study of administrative health data from 2008 to 2019. Men 65 years and older receiving continuous androgen deprivation therapy (ADT) with documented CRPC were included. An administrative proxy definition was applied to capture patients with nmCRPC and excluded those with metastatic disease. Patients were indexed upon progression to CRPC and were followed until death or end of study period to assess frequency of monitoring with PSA tests and conventional imaging. A 2-year look-back window was used to assess patterns of care leading up to CRPC as well as baseline covariates. Results: At a median follow-up of 40.1 months, 944 patients with nmCRPC were identified. Their median time from initiation of continuous ADT to CRPC was 26.0 months. 60.7% of patients had their PSA measured twice or fewer in the year prior to index, and 70.7% patients did not receive any imaging in the year following progression to CRPC. Throughout the study period, 921/944 (97.6%) patients with CRPC progressed to high-risk (HR-CRPC) with PSA doubling time ≤ 10 months, of which more than half received fewer than three PSA tests in the year prior to developing HR-CRPC, and 30.9% received no imaging in the subsequent year. Conclusion: PSA testing and imaging studies are underutilized in a real-world setting for the management of nmCRPC, including those at high risk of developing metastatic disease. Infrequent monitoring impedes proper risk stratification, disease staging and detection of treatment failure and/or metastases, thereby delaying the necessary treatment intensification with life-prolonging therapies. Adherence to guideline recommendations and the importance of timely staging should be reinforced to optimize patient outcomes.

Results from a Canadian consensus forum of key controversial areas in the management of advanced prostate cancer: Recommendations for Canadian healthcare providers.

INTRODUCTION: Rapid progress in diagnostics and therapeutics for the management of prostate cancer (PCa) has created areas where high-level evidence to guide practice is lacking. The Genitourinary Research Consortium (GURC) conducted its second Canadian consensus forum to address areas of controversy in the management of PCa and provide recommendations to guide treatment. METHODS: A panel of PCa specialists discussed topics related to the management of PCa. The core scientific committee finalized the design, questions, and analysis of the consensus results. Attendees then voted to indicate their management choice regarding each statement/topic. Questions for voting were adapted from the 2019 Advanced Prostate Cancer Consensus Conference. The thresholds for agreement were set at ≥75% for "consensus agreement," >50% for "near-consensus," and ≤50% for "no consensus." RESULTS: The panel was comprised of 29 PCa experts, including urologists (n=12), medical oncologists (n=12), and radiation oncologists (n=5). Voting took place for 65 predetermined questions and three ad hoc questions. Consensus was reached for 34 questions, spanning a variety of areas, including biochemical recurrence, treatment of metastatic castration-sensitive PCa, management of non-metastatic and metastatic castration-resistant PCa, bone health, and molecular profiling. CONCLUSIONS: The consensus forum identified areas of consensus or near-consensus in more than half of the questions discussed. Areas of consensus typically aligned with available evidence, and areas of variability may indicate a lack of high-quality evidence and point to future opportunities for further research and education.

Real-world evidence in patient-reported outcomes (PROs) of metastatic castrate-resistant prostate cancer (mCRPC) patients treated with abiraterone acetate + prednisone (AA+P) across Canada: Final results of COSMiC.

INTRODUCTION: Abiraterone acetate plus prednisone (AA+P) has shown to significantly improve survival. COSMiC, a Canadian Observational Study in Metastatic Cancer of the Prostate, set out to prospectively amass real-world data on metastatic castration-resistant prostate cancer (mCRPC) patients managed with AA+P in Canada. Herein, we report their patient-reported outcomes (PROs). METHODS: After a median followup of 67.1 weeks, 254 patients were enrolled across 39 sites. Functional Assessment of Cancer Therapy-Prostate (FACT-P), Montreal Cognitive Assessment (MoCA), Brief Pain Inventory-Short Form (BPI-SF), Brief Fatigue Inventory (BFI), and Current Health Satisfaction in Prostate Cancer (CHS-PCa) were evaluated at baseline, as well as at weeks 12, 24, 48, and 72 after AA+P initiation. Descriptive analysis was used with continuous variables. Changes from baseline were summarized using mean (standard deviation [SD]). RESULTS: At a median age of 76.6 (8.94), baseline FACT-P total score was 111.3 (19.56) with no significant change in their functional status observed from baseline over time. The median baseline MoCA score was 25.2 (4.52), yet subsequent assessments showed an absence of cognitive decline while under treatment. Similarly, no meaningful changes were detected in BPI, BFI, and CHS-PCa during the 72-week study period, thus suggesting that patients' PROs were well-maintained throughout AA+P treatment. Prostate-specific antigen (PSA) response with >50% decline was 66.4%. Safety profile was consistent with the known side effect of AA+P. CONCLUSIONS: COSMiC represents the largest Canadian mCRPC cohort treated with AA+P with real-world, prospective evaluation of PROs. This data demonstrated the maintenance in quality of life and cognitive status over the course of the study and underscores the importance of PRO use in this complex patient population.

Management algorithms for prostate-specific antigen progression in prostate cancer: Biochemical recurrence after definitive therapy and progression to non-metastatic castrate-resistant prostate cancer.

INTRODUCTION: Current prostate cancer (PCa) guidelines primarily focus on localized or metastatic PCa. A multidisciplinary genitourinary oncology panel determined that additional guidance focusing on monitoring and management of biochemical recurrence (BCR) following radical therapy and non-metastatic castration-resistant prostate cancer (nmCRPC) was warranted. METHODS: The most up-to-date national and international guidelines, consensus statements, and emerging phase 3 trials were identified and used to inform development of algorithms by a multidisciplinary genitourinary oncology panel outlining optimal monitoring and treatment for patients with non-metastatic PCa. RESULTS: A total of eight major national and international guidelines/consensus statements published since 2015 and three phase 3 trials were identified. Working group discussions among the multidisciplinary genitourinary oncology panel led to the development of two algorithms: the first addressing management of patients with BCR following radical therapy (post-BCR), and the second addressing management of nmCRPC. The post-BCR algorithm suggests consideration of early salvage treatment in select patients and provides guidance regarding observation vs. intermittent or continuous androgen-deprivation therapy (ADT). The nmCRPC algorithm suggests continued ADT and monitoring for all patients, with consideration of treatment with apalutamide or enzalutamide for patients with high-risk disease (prostate-specific antigen [PSA] doubling time of ≤ 10 months). CONCLUSIONS: Two treatment algorithms have been developed to guide the management of non-metastatic PCa and should be considered in the context of local guidelines and practice patterns.

Hsp27 regulates epithelial mesenchymal transition, metastasis, and circulating tumor cells in prostate cancer.

Defining the mechanisms underlying metastatic progression of prostate cancer may lead to insights into how to decrease morbidity and mortality in this disease. An important determinant of metastasis is epithelial-to-mesenchymal transition (EMT), and the mechanisms that control the process of EMT in cancer cells are still emerging. Here, we report that the molecular chaperone Hsp27 (HSPB1) drives EMT in prostate cancer, whereas its attenuation reverses EMT and decreases cell migration, invasion, and matrix metalloproteinase activity. Mechanistically, silencing Hsp27 decreased IL-6-dependent STAT3 phosphorylation, nuclear translocation, and STAT3 binding to the Twist promoter, suggesting that Hsp27 is required for IL-6-mediated EMT via modulation of STAT3/Twist signaling. We observed a correlation between Hsp27 and Twist in patients with prostate cancer, with Hsp27 and Twist expression each elevated in high-grade prostate cancer tumors. Hsp27 inhibition by OGX-427, an antisense therapy currently in phase II trials, reduced tumor metastasis in a murine model of prostate cancer. More importantly, OGX-427 treatment decreased the number of circulating tumor cells in patients with metastatic castration-resistant prostate cancer in a phase I clinical trial. Overall, this study defines Hsp27 as a critical regulator of IL-6-dependent and IL-6-independent EMT, validating this chaperone as a therapeutic target to treat metastatic prostate cancer.

Clusterin mediates TGF-ß-induced epithelial-mesenchymal transition and metastasis via Twist1 in prostate cancer cells.

TGF-ß promotes epithelial-mesenchymal transition (EMT) and induces clusterin (CLU) expression, linking these genes to cancer metastasis. CLU is a pleiotropic molecular chaperone that confers survival and proliferative advantage to cancer cells. However, the molecular mechanisms by which TGF-ß regulates CLU expression and CLU affects metastasis remain unknown. In this study, we report that the transcription factor Twist1 mediates TGF-ß-induced CLU expression. By binding to E-boxes in the distal promoter region of CLU gene, Twist1 regulated basal and TGF-ß-induced CLU transcription. In addition, CLU reduction reduced TGF-ß induction of the mesenchymal markers, N-cadherin and fibronectin, thereby inhibiting the migratory and invasive properties induced by TGF-ß. Targeted inhibition of CLU also suppressed metastasis in an in vivo model. Taken together, our findings indicate that CLU is an important mediator of TGF-ß-induced EMT, and suggest that CLU suppression may represent a promising therapeutic option for suppressing prostate cancer metastatic progression.

Cotargeting stress-activated Hsp27 and autophagy as a combinatorial strategy to amplify endoplasmic reticular stress in prostate cancer.

Hsp27 is a stress-activated multifunctional chaperone that inhibits treatment-induced apoptosis and causes treatment resistance in prostate and other cancers. We previously showed that targeted suppression of Hsp27 sensitizes cancer cells to hormone and chemotherapy. However, mechanisms by which Hsp27 confers cell treatment resistance are incompletely defined. Here, we report that Hsp27 protects human prostate cancer cells against proteotoxic stress induced by proteasome inhibition, and that Hsp27 silencing using siRNA or antisense (OGX-427) induced both apoptosis and autophagy through mechanisms involving reduced proteasome activity and induction of endoplasmic reticulum (ER) stress. We found that autophagy activation protected against ER stress-induced cell death, whereas inhibition of autophagy activation following Hsp27 silencing using either pharmacologic inhibitors or atg3 silencing enhanced cell death. Importantly, cotargeting Hsp27 and autophagy by combining OGX-427 with the autophagy inhibitor, chloroquine, significantly delayed PC-3 prostate tumor growth in vivo. These findings identify autophagy as a cytoprotective, stress-induced adaptive pathway, activated following disruption of protein homeostasis and ER stress induced by Hsp27 silencing. Combinatorial cotargeting cytoprotective Hsp27 and autophagy illustrates potential benefits of blocking activation of adaptive pathways to improve treatment outcomes in cancer.

Hsp27 promotes insulin-like growth factor-I survival signaling in prostate cancer via p90Rsk-dependent phosphorylation and inactivation of BAD.

Hsp27 is highly expressed in castrate-resistant prostate cancer. Although its overexpression confers resistance to androgen ablation and chemotherapy, the mechanisms by which Hsp27 inhibits treatment-induced apoptosis are incompletely defined. Castrate-resistance often correlates with increased activity of autocrine and/or paracrine growth/survival stimulatory loops including the mitogen-activated protein kinase (MAPK) and Akt pathways and insulin-like growth factor (IGF) axis components. Because Hsp27 can be activated by both MAPK and Akt pathways, it is possible that interactions between IGF-I signaling and Hsp27 phosphoactivation function to promote castrate-resistant progression. Here, we report that Hsp27 expression and phosphorylation levels correlate with IGF-I signaling and castrate-resistant progression in human prostate cancer specimens and cell lines. IGF-I induces Hsp27 phosphorylation in a time- and dose-dependent manner via p90Rsk, which interacts directly with and phosphorylates Hsp27 in vitro and in vivo. Conversely, p90Rsk inhibition using short interfering RNA or a dominant negative mutant abolishes IGF-I-induced Hsp27 phosphorylation. Hsp27 overexpression increases IGF-I-induced phosphorylation of Erk, p90Rsk, and Akt. Conversely, Hsp27 knockdown abrogates IGF-I-induced phosphorylation of Erk, p90Rsk, and Akt, thereby destabilizing Bad/14-3-3 complexes and increasing apoptotic rates. These data elucidate the interactions between Hsp27 phosphorylation and the IGF-I receptor signaling pathway and support targeting Hsp27 as a therapeutic strategy for castrate-resistant prostate cancer.

Clusterin facilitates COMMD1 and I-kappaB degradation to enhance NF-kappaB activity in prostate cancer cells.

Secretory clusterin (sCLU) is a stress-activated, cytoprotective chaperone that confers broad-spectrum cancer treatment resistance, and its targeted inhibitor (OGX-011) is currently in phase II trials for prostate, lung, and breast cancer. However, the molecular mechanisms by which sCLU inhibits treatment-induced apoptosis in prostate cancer remain incompletely defined. We report that sCLU increases NF-kappaB nuclear translocation and transcriptional activity by serving as a ubiquitin-binding protein that enhances COMMD1 and I-kappaB proteasomal degradation by interacting with members of the SCF-betaTrCP E3 ligase family. Knockdown of sCLU in prostate cancer cells stabilizes COMMD1 and I-kappaB, thereby sequestrating NF-kappaB in the cytoplasm and decreasing NF-kappaB transcriptional activity. Comparative microarray profiling of sCLU-overexpressing and sCLU-knockdown prostate cancer cells confirmed that the expression of many NF-kappaB-regulated genes positively correlates with sCLU levels. We propose that elevated levels of sCLU promote prostate cancer cell survival by facilitating degradation of COMMD1 and I-kappaB, thereby activating the canonical NF-kappaB pathway.

Cooperative interactions between androgen receptor (AR) and heat-shock protein 27 facilitate AR transcriptional activity.

Androgen receptor (AR) transactivation is known to enhance prostate cancer cell survival. However, the precise effectors by which the prosurvival effects of androgen and AR drive prostate cancer progression are poorly defined. Here, we identify a novel feed-forward loop involving cooperative interactions between ligand-activated AR and heat-shock protein 27 (Hsp27) phospho-activation that enhance AR stability, shuttling, and transcriptional activity, thereby increasing prostate cancer cell survival. Androgen-bound AR induces rapid Hsp27 phosphorylation on Ser(78) and Ser(82) residues in an AR- and p38 kinase-dependent manner. After this androgen-induced, non-nuclear phospho-activation, Hsp27 displaces Hsp90 from a complex with AR to chaperone AR into the nucleus and interact with its response elements to enhance its genomic activity. Inhibition of Hsp27 phosphorylation, or knockdown using the antisense drug OGX-427, shifted the association of AR with Hsp90 to MDM2, increased proteasome-mediated AR degradation, decreased AR transcriptional activity, and increased prostate cancer LNCaP cell apoptotic rates. OGX-427 treatment of mice bearing LNCaP xenografts transfected with an androgen-regulated, probasin-luciferase reporter construct resulted in decreased bioluminescence and serum PSA levels as pharmacodynamic readouts of AR activity, as well as AR, Hsp27, and Hsp90 protein levels in LNCaP tumor tissue. These data identify novel nongenomic mechanisms involving androgen, AR, and Hsp27 activation that cooperatively interact to regulate the genomic activity of AR and justify further investigation of Hsp27 knockdown as an AR disrupting therapeutic strategy in prostate cancer.