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The role of endogenous testosterone in de novo prostate cancer pathogenesis in humans remains unclear. The effect of testosterone on the tumor genome is not explored. We sought to explore the correlation between perioperative testosterone level and genomic risk score in a cohort of men who underwent radical prostatectomy.We included patients who underwent radical prostatectomy (2013-2018) and had adverse pathological features in their final surgical specimens (positive margin, and/or pT3a or higher). The outcome of interest was the genomic risk score: low (0.45), intermediate (0.45-0.6) and high (0.6). The associations between serum testosterone level and 188 gene expression-based signatures were examined. Secondary outcomes of interest included biochemical recurrence and receipt of secondary treatment.The median genomic risk score was lower in the low testosterone group compared to the intermediate and normal testosterone groups (0.38 vs 0.52 vs 0.53, respectively; p=0.049). There was no difference in biochemical recurrence-free survival between the 3 testosterone groups (p=0.9). Patients with low testosterone levels had higher odds of receiving secondary treatment (OR: 2.27; 95% CI: 1.14-4.50; p=0.02) than those with normal levels. A total of 43 (of 188) gene expression signatures were associated with testosterone level (p0.05). In total, 33 signatures were positively associated with serum testosterone levels, including 12 signatures involved in DNA repair pathways.This is the first study to assess the correlation of preoperative testosterone level on the tumor transcriptome and showed no clinical correlation between pre-defined genomic risk score groups and testosterone groups. This study adds to the notion of the limited role of endogenous testosterone on the development of de novo high-risk localized prostate cancer.

Resistance to cancer treatment remains a major clinical hurdle. Here, we demonstrate that the CoREST complex is a key determinant for endocrine resistance and ER+ breast cancer plasticity. In endocrine sensitive cells, CoREST is recruited to ERα/FOXA1 co-bound regulatory regions to regulate the estrogen pathway. In contrast, during temporal reprogramming towards a resistant state, CoREST is recruited to AP-1 sites. In reprogrammed cells, CoREST favors chromatin opening, cJUN binding to chromatin, and gene activation by controlling SWI/SNF recruitment independently of the demethylase activity of the CoREST subunit, LSD1. Genetic and pharmacological CoREST inhibition reduce tumorigenesis and metastasis of endocrine sensitive and resistant xenografts models. Consistently, CoREST controls a gene signature in clinical breast tumors resistant to endocrine therapies involved in invasiveness. Our studies reveal CoREST functions that are co-opted to drive cellular plasticity and resistance to endocrine therapies and tumorigenesis, thus establishing CoREST as a potential therapeutic target for the treatment of advanced breast cancer.

Castration-resistant prostate cancer (CRPC) is associated with an increased reliance on protein homeostasis (aka proteostasis) factors, such as heat shock protein 70 (Hsp70), but it is not clear what other factors might be involved. To address this question, we perform functional and synthetic lethal screens in four prostate cancer cell lines. These screens confirm key roles for Hsp70, Hsp90 and their co-chaperones, but also suggest that the mitochondrial chaperone, Hsp60/HSPD1 is selectively required in CRPC cell lines. Knockdown of Hsp60 does not impact the stability of androgen receptor (AR) or its variants; rather, it is associated with loss of mitochondrial spare respiratory capacity, partly due to increased proton leakage. Finally, transcriptional data reveals a correlation between Hsp60 levels and poor survival of prostate cancer patients. These findings suggest that re-wiring of the proteostasis network is associated with CRPC, creating selective vulnerabilities that might be targeted to treat the disease.

BACKGROUND Small cell neuroendocrine (NE) carcinomas of the prostate classically lose androgen receptor (AR) expression, may harbor loss of the RB1, TP53, and PTEN tumor suppressor genes, and are associated with a poor prognosis. However usual-type adenocarcinomas may also contain areas of NE differentiation, and in this context the molecular features and biological significance are less certain. METHODS We examined the molecular phenotype and oncologic outcomes of primary prostate adenocarcinomas with ≥5% NE differentiation (≥5% chromogranin A-positive NE cells in any given tumor spot on tissue microarray) using three independent study sets: a set of tumors with paneth cell-like NE differentiation (n = 26), a retrospective case-cohort of intermediate- and high-risk patients enriched for adverse outcomes (n = 267), and primary tumors from a retrospective series of men with eventual castration-resistant metastatic prostate cancer (CRPC) treated with abiraterone or enzalutamide (n = 55). RESULTS Benign NE cells expressed significantly lower quantified AR levels compared with paired benign luminal cells (P

Multiparametric magnetic resonance imaging is a diagnostic tool for prostate cancer with limited data on prognostic use. We sought to determine whether multiparametric magnetic resonance could predict aggressive prostate cancer features.We retrospectively analyzed the records of 206 patients who underwent radical prostatectomy between 2013 and 2017. All patients had available RNA expression data on the final pathology specimen obtained from a location corresponding to a lesion location on multiparametric magnetic resonance imaging. The association between the PIRADS™ (Prostate Imaging Reporting and Data System) score and adverse pathology features were analyzed. We also performed differential transcriptomic analysis between the PIRADS groups. Factors associated with adverse pathology were analyzed using a multivariable logistic regression model.Lesion size (p = 0.03), PIRADS score (p = 0.02) and extraprostatic extension (p = 0.01) associated significantly with the Decipher® score. Multivariable analysis showed that the PIRADS score (referent PIRADS 3, OR 8.1, 95% CI 1.2-57.5, p = 0.04), the Gleason Grade Group (referent 3, OR 5.6, 95% CI 1.5-21.1, p = 0.01) and prostate specific antigen (OR 1.103, 95% CI 1.011-1.203) were risk factors for adverse pathology findings. The difference between PIRADS 4 and 5 did not reach significance (OR 1.9, 95% CI 0.8-4.5, p = 0.12). However, the PI3K-AKT-mTOR, WNT-β and E2F signaling pathways were more active in PIRADS 5 than in PIRADS 4 cases.The PIRADS score is associated with adverse pathology results, increased metastatic risk and differential genomic pathway activation.

5041 Background: The MYC oncogene is one of the most commonly amplified genes in PCa, contributes to androgen independent growth, and is potentially targetable. We sought to define the molecular, immunologic, and clinicodemographic landscape of MYCamp in advanced PCa to better understand progression and establish rationale for personalized treatments and combinations. Methods: Hybrid capture-based comprehensive genomic profiling (CGP) was performed on tumor samples from predominantly advanced PCa samples. MYCamp was defined as copy number (CN) ≥6. PD-L1 IHC was performed using Dako 22C3. A subset of patients (pts) with advanced PCa were selected from the Flatiron Health- Foundation Medicine (FM) clinicogenomic database (CGDB), a nationwide de-identified EHR-derived clinical DB linked to FM CGP data for pts treated from 01/2011-12/2020. The de-identified data originated from approximately 280 US cancer clinics (̃800 sites of care). Results: The genomic profiles of 12,528 tissue samples from unique PCa pts (including hormone sensitive and castrate resistant) were evaluated. MYCamp was detected in 10.6%, with a median MYC CN of 8. Median age was 67 years (67 for MYCwt versus 68 for MYCamp). MYCamp occurred at a higher frequency in men with African (N = 190/1,473, 12.9%) versus European (N = 996/9,796, 10.2%) ancestry (P = 0.002), was more frequent in metastatic biopsy sites vs primary (15.7% vs 6.2%, P < 0.001), and was most common in liver mets (20.2%). MYCamp CN > 15 was enriched for PD-L1 positivity (26.1%) compared with MYCwt (9.8%) or MYCamp CN 6-15 (11.5%) (CN > 15 vs wt P = 0.025). In pts with MYCamp vs MYCwt PCa AR, RAD21, PTEN, CCND1, ZNF703, FGF19, FGFR1, and FGF3 each had significantly higher rates of CN changes (all p < 0.001); TP53 mutation was also more common with MYCamp (47.5% vs 39.7%, P < 0.001). MYCamp tumors were less likely to harbor microsatellite instability vs MYCwt (0.8% vs 2.4%, P < 0.001) and had higher tumor mutational burden (median 2.6 vs 1.7 mut/Mb, P < 0.001). In liquid samples with evidence of circulating tumor DNA (compositive tumor fraction [cTF] > 0) from PCa pts MYCamp was detected in 2.0% (28/1,402), and in 4.5% (20/445) with cTF > 20%. Among evaluable PCa pts in the CGDB, (67 MYCamp and 658 MYCwt) MYCamp did not significantly impact treatment decisions, with the majority receiving novel hormone therapies (35.8% MYCamp vs. 31.5% MYCwt) or chemotherapy containing regimens (37.3% MYCamp vs. 27.7% MYCwt) as first therapy after CGP report. Conclusions: Herein, we report the largest analysis to date of molecular, immunologic, and clinicodemographic features of MYCamp advanced PCa. These findings suggest that MYCamp defines a biologically distinct subset of PCa pts for whom personalized combination treatments utilizing targeted and/or immunotherapies may be effective. Independent cohorts are needed to validate these findings.

INTRODUCTION AND OBJECTIVES:Progression of prostate cancer is a complex multistep process that involves molecular alterations in cells of the tumor and microenvironment, however the significance of...

Background: Socioeconomic, environmental, and healthcare utilization factors are likely drivers of the persistent prostate cancer disparities between African-American (AA) and European-American (EA) men. Tumor molecular heterogeneity may also contribute, and Eurocentric studies and initiatives have the potential to widen disparities through the development of prognostic signatures and targeted therapeutics that do not account for genetic diversity. Methods: The Decipher Genomics Resource Information Database (GRID) contains tumor mRNA expression and clinical data generated through use of the Decipher test to predict prostate cancer prognosis. We matched 426 AA and 426 EA patients with localized prostate cancer using a propensity score accounting for age and tumor clinicopathological factors. We then applied five validated prostate cancer molecular subtype classifiers by Alshalalfa et al (Neuroendocrine, Adenocarcinoma), Kamoun et al (S1-S3), Tomlins et al(ERG+, ETS+, SPINK1+, ERG-/ETS-/SPINK1-), You et al (PCS1-PCS3), and Zhang et al (Basal, Luminal) to assign tumor subtypes. Heterogeneity in subtype frequency by self-identified race (SIR) was evaluated using chi-squared tests. Differences in subtype prognostic value by SIR were evaluated in logistic regression models using a high Decipher tumor genomic risk score of ≥0.6 as a surrogate for higher risk of metastases. Results: AA men were more likely to have a Decipher score ≥0.6 than EA men (25.6% vs. 20.0%, p Conclusions: Prostate cancer molecular subtype distributions differed by SIR, with AA men generally more likely to have aggressive subtypes across classification schemes. Furthermore, AA and EA had a heterogeneous risk of metastases (defined by Decipher genomic risk score) for several subtypes. Further research is needed to better define subtyping classifiers and the prognostic value thereof in AA men. Citation Format: Kevin H. Kensler, Mohamed Alshalalfa, Brandon A. Mahal, Yang Liu, Elai Davicioni, Shivanshu Awasthi, Kosj Yamoah, Timothy R. Rebbeck. Racial variation in molecularly-defined prostate cancer subtypes [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3509.