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The widespread use of potent androgen receptor signaling inhibitors (ARSIs) has led to an increasing emergence of AR-independent castration-resistant prostate cancer (CRPC), typically driven by loss of AR expression, lineage plasticity, and transformation to prostate cancers (PCs) that exhibit phenotypes of neuroendocrine or basal-like cells. The anti-apoptotic protein BCL2 is upregulated in neuroendocrine cancers and may be a therapeutic target for this aggressive PC disease subset. There is an unmet clinical need, therefore, to clinically characterize BCL2 expression in metastatic CRPC (mCRPC), determine its association with AR expression, uncover its mechanisms of regulation, and evaluate BCL2 as a therapeutic target and/or biomarker with clinical utility. Here, using multiple PC biopsy cohorts and models, we demonstrate that BCL2 expression is enriched in AR-negative mCRPC, associating with shorter overall survival and resistance to ARSIs. Moreover, high BCL2 expression associates with lineage plasticity features and neuroendocrine marker positivity. We provide evidence that BCL2 expression is regulated by DNA methylation, associated with epithelial-mesenchymal transition, and increased by the neuronal transcription factor ASCL1. Finally, BCL2 inhibition had antitumor activity in some, but not all, BCL2-positive PC models, highlighting the need for combination strategies to enhance tumor cell apoptosis and enrich response.

Background: PTEN loss and aberrations in PI3K/AKT signaling kinases associate with poorer response to abiraterone acetate (AA) in metastatic castration-resistant prostate cancer (mCRPC). In this study, we assessed antitumor activity of the AKT inhibitor capivasertib combined with enzalutamide in mCRPC with prior progression on AA and docetaxel., Methods: This double-blind, placebo-controlled, randomized phase 2 trial, recruited men ≥ 18 years with progressing mCRPC and performance status 0-2 from 15 UK centers. Randomized participants (1:1) received enzalutamide (160 mg orally, once daily) with capivasertib (400 mg)/ placebo orally, twice daily on an intermittent (4 days on, 3 days off) schedule. Primary endpoint was composite response rate (RR): RECIST 1.1 objective response, ≥ 50 % PSA decrease from baseline, or circulating tumor cell count conversion (from ≥ 5 at baseline to < 5 cells/7.5 mL). Subgroup analyses by PTEN IHC status were pre-planned., Results: Overall, 100 participants were randomized (50:50); 95 were evaluable for primary endpoint (47:48); median follow-up was 43 months. RR were 9/47 (19.1 %) enzalutamide/capivasertib and 9/48 (18.8 %) enzalutamide/placebo (absolute difference 0.4 % 90 %CI -12.8 to 13.6, p = 0.58), with similar results in the PTEN IHC loss subgroup. Irrespective of treatment, OS was significantly worse for PTEN IHC loss (10.1 months [95 %CI: 4.6-13.9] vs 14.8 months [95 %CI: 10.8-18]; p = 0.02). Most common treatment-emergent grade ≥ 3 adverse events for the combination were diarrhea (13 % vs 2 %) and fatigue (10 % vs 6 %)., Conclusions: Combined capivasertib/enzalutamide was well tolerated but didn't significantly improve outcomes from abiraterone pre-treated mCRPC., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: JdB reports advisory board fees from many companies including Acai Therapeutics, Amgen, Astra Zeneca, Astellas, Bayer, Bioxcel Therapeutics, Boehringer Ingelheim, Cellcentric, Crescendo, Daiichi, Dark Blue Therapeutics, Eisai, Genentech/Roche, Genmab, GSK, Harpoon, ImCheck Therapeutics, Janssen, Merck Serono, Merck Sharp & Dohme, Menarini/Silicon Biosystems, MetaCurUm, Myricx, Novartis, Nurix Therapeutics, Oncternal, Orion, Pfizer, Qiagen, Sanofi Aventis, Sierra Oncology, Taiho, Takeda, Tango Therapeutics, Terumo, Vertex Pharmaceuticals. He is an employee of The ICR, which have received funding or other support for his research work from Acai Therapeutics, Amgen, AstraZeneca, Astellas, Bayer, Cellcentric, Crescendo, Daiichi, Genentech, Genmab, GSK, Harpoon, Immunic Therapeutics, Janssen, Merck Serono, Merck Sharp & Dohme, Menarini/Silicon Biosystems, MetaCurUm, Myricx, Nurix Therapeutics, Oncternal, Orion, Pfizer, Qiagen, Sanofi Aventis, Sierra Oncology, Taiho, Vertex Pharmaceuticals. The ICR have a commercial interest in abiraterone, PARP inhibition in DNA repair defective cancers and PI3K/AKT pathway inhibitors (no personal income). JDB was named as an inventor, with no financial interest for patent 8,822,438, submitted by Janssen that covers the use of abiraterone acetate with corticosteroids. EH reports that their institution has received an Investigator Initiated Research grant (IIR) from AstraZeneca for the central coordination of the trial. EH reports grants received by their institution as contribution to support central trial costs for non-commercial trials from Accuray, Varian Medical Systems, AstraZeneca, Janssen-Cilag, Bayer, Roche Products, and Merck Sharp and Dohm. SJ reports advisory boards and speaker fees received from AAA/Novartis, Accord, Astellas, Astra Zeneca, Bayer, Boston Scientific, Janssen and Pfizer, as well as consultancy fees received from Boston Scientific and BXT Nanotherapy. SJ also reports conferences travel received from Bayer and Janssen. AJB reports honoraria from Janssen-Cilag, consulting or advisory roles from Roche, Astellas Medivation, Janssen Oncology, AstraZeneca, Sanofi, Bayer Schering Pharma, Bristol-Myers-Squib, Merck Serono and Pfizer. AJB also reports speakers’ fees received from Bayer, Janssen Oncology and Pfizer. RJ reports honoraria from Astellas Pharma, Janssen, AstraZeneca, MSD Oncology, Bristol Myers Squibb, Pfizer, Novartis, Ipsen, Bayer, Roche/Genentech, Merck Serono, Eisai, WebMD, Advanced Accelerator Applications/Novartis and Elsevier. RJ also reports speakers’ fees received from Merck Serono, Pfizer, Janssen, Astellas Pharma, MSD Oncology, AstraZeneca, Ipsen, Bristol Myers Squibb/Celgene and Bayer. RJ also reports research Funding received from Roche (Inst), Astellas Pharma (Inst), AstraZeneca (Inst), Exelixis (Inst), Clovis Oncology (Inst) and Bayer (Inst), as well as travel, accommodations and expenses received from Ipsen, Bayer, Janssen, Astellas Pharma, MSD, Merck Serono and Pfizer. PR, NP, LF, AE, SM, PF, JG, JN, RR, BG, DR, IF, SC, CB, AF, MC, SC, ZM, CR, UMC, PH, PS, EC and DML have no conflicts to declare., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

BACKGROUNDClinical trials have suggested antitumor activity from PARP inhibition beyond homologous recombination deficiency (HRD). RNASEH2B loss is unrelated to HRD and preclinically sensitizes to PARP inhibition. The current study reports on RNASEH2B protein loss in advanced prostate cancer and its association with RB1 protein loss, clinical outcome, and clonal dynamics during treatment with PARP inhibition in a prospective clinical trial.METHODSWhole tumor biopsies from multiple cohorts of patients with advanced prostate cancer were interrogated using whole-exome sequencing (WES), RNA-Seq (bulk and single nucleus), and IHC for RNASEH2B and RB1. Biopsies from patients treated with olaparib in the TOPARP-A and TOPARP-B clinical trials were used to evaluate RNASEH2B clonal selection during olaparib treatment.RESULTSShallow codeletion of RNASEH2B and adjacent RB1 - colocated at chromosome 13q14 - was common, deep codeletion infrequent, and gene loss associated with lower mRNA expression. In castration-resistant prostate cancer (CRPC) biopsies, RNASEH2B and RB1 mRNA expression correlated, but single nucleus RNA-Seq indicated discordant loss of expression. IHC studies showed that loss of the 2 proteins often occurred independently, arguably due to stochastic second allele loss. Pre- and posttreatment metastatic CRPC (mCRPC) biopsy studies from BRCA1/2 WT tumors, treated on the TOPARP phase II trial, indicated that olaparib eradicated RNASEH2B-loss tumor subclones.CONCLUSIONPARP inhibition may benefit men suffering from mCRPC by eradicating tumor subclones with RNASEH2B loss.TRIAL REGISTRATIONClinicaltrials.gov NCT01682772.FUNDINGAstraZeneca; Cancer Research UK; Medical Research Council; Cancer Research UK; Prostate Cancer UK; Movember Foundation; Prostate Cancer Foundation.

Inflammation is a hallmark of cancer 1 . In patients with cancer, peripheral blood myeloid expansion, indicated by a high neutrophil-to-lymphocyte ratio, associates with shorter survival and treatment resistance across malignancies and therapeutic modalities 2-5 . Whether myeloid inflammation drives progression of prostate cancer in humans remain unclear. Here we show that inhibition of myeloid chemotaxis can reduce tumour-elicited myeloid inflammation and reverse therapy resistance in a subset of patients with metastatic castration-resistant prostate cancer (CRPC). We show that a higher blood neutrophil-to-lymphocyte ratio reflects tumour myeloid infiltration and tumour expression of senescence-associated mRNA species, including those that encode myeloid-chemoattracting CXCR2 ligands. To determine whether myeloid cells fuel resistance to androgen receptor signalling inhibitors, and whether inhibiting CXCR2 to block myeloid chemotaxis reverses this, we conducted an investigator-initiated, proof-of-concept clinical trial of a CXCR2 inhibitor (AZD5069) plus enzalutamide in patients with metastatic CRPC that is resistant to androgen receptor signalling inhibitors. This combination was well tolerated without dose-limiting toxicity and it decreased circulating neutrophil levels, reduced intratumour CD11b + HLA-DR lo CD15 + CD14 - myeloid cell infiltration and imparted durable clinical benefit with biochemical and radiological responses in a subset of patients with metastatic CRPC. This study provides clinical evidence that senescence-associated myeloid inflammation can fuel metastatic CRPC progression and resistance to androgen receptor blockade. Targeting myeloid chemotaxis merits broader evaluation in other cancers., (© 2023. The Author(s).)

Background: Germline mutations in the ataxia telangiectasia mutated ( ATM ) gene occur in 0.5-1% of the overall population and are associated with tumour predisposition. The clinical and pathological features of ATM -mutated prostate cancer (PC) are poorly defined but have been associated with lethal PC., Objective: To report on the clinical characteristics including family history and clinical outcomes of a cohort of patients with advanced metastatic castration-resistant PC (CRPC) who were found to have germline ATM mutations after mutation detection by initial tumour DNA sequencing., Design Setting and Participants: We acquired germline ATM mutation data by saliva next-generation sequencing from patients with ATM mutations in PC biopsies sequenced between January 2014 and January 2022. Demographics, family history, and clinical data were collected retrospectively., Outcome Measurements and Statistical Analysis: Outcome endpoints were based on overall survival (OS) and time from diagnosis to CRPC. Data were analysed using R version 3.6.2 (R Foundation for Statistical Computing, Vienna, Austria)., Results and Limitations: Overall, seven patients ( n  = 7/1217; 0.6%) had germline ATM mutations detected, with five of them having a family history of malignancies, including breast, prostate, pancreas, and gastric cancer; leukaemia; and lymphoma. Two patients had concomitant somatic mutations in tumour biopsies in genes other than ATM , while two patients were found to carry more than one ATM pathogenic mutation. Five tumours in germline ATM variant carriers had loss of ATM by immunohistochemistry. The median OS from diagnosis was 7.1 yr (range 2.9-14 yr) and the median OS from CRPC was 5.3 yr (range 2.2-7.3 yr). When comparing these data with PC patients sequenced by The Cancer Genome Atlas, we found that the spatial localisation of mutations was similar, with distribution of alterations occurring on similar positions in the ATM gene. Interestingly, these include a mutation within the FRAP-ATM-TRRAP (FAT) domain, suggesting that this represents a mutational hotspot for ATM ., Conclusions: Germline ATM mutations are rare in patients with lethal PC but occur at mutational hotspots; further research is warranted to better characterise the family histories of these men and PC clinical course., Patient Summary: In this report, we studied the clinical and pathological features of advanced prostate cancers associated with germline mutations in the ATM gene. We found that most patients had a strong family history of cancer and that this mutation might predict the course of these prostate cancers, as well as response to specific treatments., (© 2023 The Author(s).)

Background: B7-H3 is a cell surface immunomodulatory glycoprotein overexpressed in prostate cancers (PCs). Understanding its longitudinal expression at emergence of castration resistance and association with tumour genomics are critical to the development of and patient selection for B7-H3 targeted therapies., Objective: To characterise B7-H3 expression in same-patient hormone-sensitive (HSPC) and castration-resistant (CRPC) PC biopsies, associating this with PC genomics, and to evaluate the antitumour activity of an anti-B7-H3 antibody-drug conjugate (ADC) in human CRPC in vitro and in vivo., Design, Setting, and Participants: We performed immunohistochemistry and next-generation sequencing on a cohort of 98 clinically annotated CRPC biopsies, including 72 patients who also had HSPC biopsies for analyses. We analysed two CRPC transcriptome and exome datasets, and PC scRNASeq datasets. PC organoids (patient-derived xenograft [PDX]-derived organoids [PDX-Os]) were derived from PDXs generated from human CRPC biopsies., Outcome Measurements and Statistical Analysis: We evaluated B7-H3 mRNA expression in relation to a panel of 770 immune-related genes, compared B7-H3 protein expression between same-patient HSPC and CRPC biopsies, determined associations with PC genomic alterations, and evaluated the antitumour activity of DS-7300a, a topoisomerase-1 inhibitor payload anti-B7-H3 ADC, in human PC cell lines, organoids (PDX-Os), and xenografts (PDXs) of different histologies, B7-H3 expressions, and genomics., Results and Limitations: B7-H3 was among the most highly expressed immunomodulatory genes in CRPCs. Most CRPCs (93%) expressed B7-H3, and in patients who developed CRPC, B7-H3 expression was frequently expressed at the time of HSPC diagnosis (97%). Conversion from B7-H3 positive to negative, or vice versa, during progression from HSPC to CRPC was uncommon. CRPC with neuroendocrine features were more likely to be B7-H3 negative (28%) than adenocarcinomas. B7-H3 is overexpressed in tumours with defective DNA repair gene (ATM and BRCA2) alterations and is associated with ERG expression, androgen receptor (AR) expression, and AR activity signature. DS7300a had antitumour activity against B7-H3 expressing human PC models including cell lines, PDX-Os, and PDXs of adenocarcinoma and neuroendocrine histology., Conclusions: The frequent overexpression of B7-H3 in CRPC compared with normal tissue and other B7 family members implicates it as a highly relevant therapeutic target in these diseases. Mechanisms driving differences in B7-H3 expression across genomic subsets warrant investigation for understanding the role of B7-H3 in cancer growth and for the clinical development of B7-H3 targeted therapies., Patient Summary: B7-H3, a protein expressed on the surface of the most lethal prostate cancers, in particular those with specific mutations, can be targeted using drugs that bind B7-H3. These findings are relevant for the development of such drugs and for deciding which patients to treat with these new drugs., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Metastatic castration-resistant prostate cancer (mCRPC) is a heterogeneous disease in which molecular stratification is needed to improve clinical outcomes. The identification of predictive biomarkers can have a major impact on the care of these patients, but the availability of metastatic tissue samples for research in this setting is limited., Objective: To study the prevalence of immune biomarkers of potential clinical utility to immunotherapy in mCRPC and to determine their association with overall survival (OS)., Design, Setting, and Participants: From 100 patients, mCRPC biopsies were assayed by whole exome sequencing, targeted next-generation sequencing, RNA sequencing, tumor mutational burden, T-cell-inflamed gene expression profile (TcellinfGEP) score (Nanostring), and immunohistochemistry for programmed cell death 1 ligand 1 (PD-L1), ataxia-telangiectasia mutated (ATM), phosphatase and tensin homolog (PTEN), SRY homology box 2 (SOX2), and the presence of neuroendocrine features., Outcome Measurements and Statistical Analysis: The phi coefficient determined correlations between biomarkers of interest. OS was assessed using Kaplan-Meier curves and adjusted hazard ratios (aHRs) from Cox regression., Results and Limitations: PD-L1 and SOX2 protein expression was detected by immunohistochemistry (combined positive score ≥1 and >5% cells, respectively) in 24 (33%) and 27 (27%) mCRPC biopsies, respectively; 23 (26%) mCRPC biopsies had high TcellinfGEP scores (>-0.318). PD-L1 protein expression and TcellinfGEP scores were positively correlated (phi 0.63 [0.45; 0.76]). PD-L1 protein expression (aHR: 1.90 [1.05; 3.45]), high TcellinfGEP score (aHR: 1.86 [1.04; 3.31]), and SOX2 expression (aHR: 2.09 [1.20; 3.64]) were associated with worse OS., Conclusions: PD-L1, TcellinfGEP score, and SOX2 are prognostic of outcome from the mCRPC setting. If validated, predictive biomarker studies incorporating survival endpoints need to take these findings into consideration., Patient Summary: This study presents an analysis of immune biomarkers in biopsies from patients with metastatic prostate cancer. We describe tumor alterations that predict prognosis that can impact future studies., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Data suggest that immunomodulation induced by DNA hypomethylating agents can sensitize tumors to immune checkpoint inhibitors. We conducted a phase 1 dose-escalation trial (NCT02998567) of guadecitabine and pembrolizumab in patients with advanced solid tumors. We hypothesized that guadecitabine will overcome pembrolizumab resistance., Methods: Patients received guadecitabine (45 mg/m 2 or 30 mg/m 2 , administered subcutaneously on days 1-4), with pembrolizumab (200 mg administered intravenously starting from cycle 2 onwards) every 3 weeks. Primary endpoints were safety, tolerability and maximum tolerated dose; secondary and exploratory endpoints included objective response rate (ORR), changes in methylome, transcriptome, immune contextures in pre-treatment and on-treatment tumor biopsies., Results: Between January 2017 and January 2020, 34 patients were enrolled. The recommended phase II dose was guadecitabine 30 mg/m 2 , days 1-4, and pembrolizumab 200 mg on day 1 every 3 weeks. Two dose-limiting toxicities (neutropenia, febrile neutropenia) were reported at guadecitabine 45 mg/m 2 with none reported at guadecitabine 30 mg/m 2 . The most common treatment-related adverse events (TRAEs) were neutropenia (58.8%), fatigue (17.6%), febrile neutropenia (11.8%) and nausea (11.8%). Common, grade 3+ TRAEs were neutropaenia (38.2%) and febrile neutropaenia (11.8%). There were no treatment-related deaths. Overall, 30 patients were evaluable for antitumor activity; ORR was 7% with 37% achieving disease control (progression-free survival) for ≥24 weeks. Of 12 evaluable patients with non-small cell lung cancer, 10 had been previously treated with immune checkpoint inhibitors with 5 (42%) having disease control ≥24 weeks (clinical benefit). Reduction in LINE - 1 DNA methylation following treatment in blood (peripheral blood mononuclear cells) and tissue samples was demonstrated and methylation at transcriptional start site and 5' untranslated region gene regions showed enriched negative correlation with gene expression. Increases in intra-tumoural effector T-cells were seen in some responding patients. Patients having clinical benefit had high baseline inflammatory signature on RNAseq analyses., Conclusions: Guadecitabine in combination with pembrolizumab is tolerable with biological and anticancer activity. Reversal of previous resistance to immune checkpoint inhibitors is demonstrated., Competing Interests: Competing interests: DP-P: Has served on advisory boards for Takeda, Pfizer, Astra-Zeneca, Boehringer-Ingelheim, Roche. Has received honoraria from Boehringer-Ingelheim, Amgen, Pfizer, Astra-Zeneca, Takeda. Has received research funding (coapplicant) from Amgen. All unrelated to this work. CY: Has served as a consultant/independent contractor with Faron Pharmaceuticals, and as an honorarium recipient with Celgene. All unrelated to this work. MCP: Has served on advisory Board for BMS and Eisai, All unrelated to this work. RB: Has received funding from Cancer Research UK, Ovarian Cancer action and Astra Zeneca. All unrelated to this work. UB: Has received honoraria fron Astellas, Novartis, Karus Therapuetics, Pheonix Solutions, Eli Lilly, Astex, Vernalis, Boehringer IngelheimIs a recipient of an NIHR Research Professorship Award and has received CRUK funding: Cancer Research UK Scientific Executive Board, Cancer Research UK Centre Award. Cancer Research UK Drug Discovery Committee-Programme Award. All unrelated to this work JL: Research grant funding from Roche, Basilea, and Genmab unrelated to this workIs an editor for BJCJ de Bono: JdB has served on advisory boards and received fees from many companies including Astra Zeneca, Astellas, Bayer, Bioxcel Therapeutics, Boehringer Ingelheim, Cellcentric, Daiichi, Eisai, Genentech/Roche, Genmab, GSK, Janssen, Merck Serono, Merck Sharp & Dohme, Menarini/Silicon Biosystems, Orion, Pfizer, Qiagen, Sanofi Aventis, Sierra Oncology, Taiho, Vertex Pharmaceuticals. He is an employee of The ICR, which have received funding or other support for his research work from AZ, Astellas, Bayer, Cellcentric, Daiichi, Genentech, Genmab, GSK, Janssen, Merck Serono, MSD, Menarini/Silicon Biosystems, Orion, Sanofi Aventis, Sierra Oncology, Taiho, Pfizer, Vertex, and which has a commercial interest in abiraterone, PARP inhibition in DNA repair defective cancers and PI3K/AKT pathway inhibitors (no personal income). He was named as an inventor, with no financial interest, for patent 8,822,438. He has been the CI/PI of many industry sponsored clinical trials. JDB is a National Institute for Health Research (NIHR) Senior Investigator. AM: Has served on advisory boards for Janssen Pharmaceuticals, Merck Pharmaceuticals, Genmab Pharmaceuticals and Takeda Pharmaceuticals. Has received honoraria from Chugai Pharmaceuticals, Novartis Oncology, Faron Pharmaceuticals, Bayer Pharmaceuticals. Has received expenses from Amgen Pharmaceuticals and LOXO Oncology. All unrelated to this work., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

The bromodomain and extraterminal (BET) family of chromatin reader proteins bind to acetylated histones and regulate gene expression. The development of BET inhibitors (BETi) has expanded our knowledge of BET protein function beyond transcriptional regulation and has ushered several prostate cancer (PCa) clinical trials. However, BETi as a single agent is not associated with antitumor activity in patients with castration-resistant prostate cancer (CRPC). We hypothesized novel combinatorial strategies are likely to enhance the efficacy of BETi. By using PCa patient-derived explants and xenograft models, we show that BETi treatment enhanced the efficacy of radiation therapy (RT) and overcame radioresistance. Mechanistically, BETi potentiated the activity of RT by blocking DNA repair. We also report a synergistic relationship between BETi and topoisomerase I (TOP1) inhibitors (TOP1i). We show that the BETi OTX015 synergized with the new class of synthetic noncamptothecin TOP1i, LMP400 (indotecan), to block tumor growth in aggressive CRPC xenograft models. Mechanistically, BETi potentiated the antitumor activity of TOP1i by disrupting replication fork stability. Longitudinal analysis of patient tumors indicated that TOP1 transcript abundance increased as patients progressed from hormone-sensitive prostate cancer to CRPC. TOP1 was highly expressed in metastatic CRPC, and its expression correlated with the expression of BET family genes. These studies open new avenues for the rational combinatorial treatment of aggressive PCa.

It has been recognized for decades that ERBB signaling is important in prostate cancer, but targeting ERBB receptors as a therapeutic strategy for prostate cancer has been ineffective clinically. However, we show here that membranous HER3 protein is commonly highly expressed in lethal prostate cancer, associating with reduced time to castration resistance (CR) and survival. Multiplex immunofluorescence indicated that the HER3 ligand NRG1 is detectable primarily in tumor-infiltrating myelomonocytic cells in human prostate cancer; this observation was confirmed using single-cell RNA sequencing of human prostate cancer biopsies and murine transgenic prostate cancer models. In castration-resistant prostate cancer (CRPC) patient-derived xenograft organoids with high HER3 expression as well as mouse prostate cancer organoids, recombinant NRG1 enhanced proliferation and survival. Supernatant from murine bone marrow-derived macrophages and myeloid-derived suppressor cells promoted murine prostate cancer organoid growth in vitro , which could be reversed by a neutralizing anti-NRG1 antibody and ERBB inhibition. Targeting HER3, especially with the HER3-directed antibody-drug conjugate U3-1402, exhibited antitumor activity against HER3-expressing prostate cancer. Overall, these data indicate that HER3 is commonly overexpressed in lethal prostate cancer and can be activated by NRG1 secreted by myelomonocytic cells in the tumor microenvironment, supporting HER3-targeted therapeutic strategies for treating HER3-expressing advanced CRPC. SIGNIFICANCE: HER3 is an actionable target in prostate cancer, especially with anti-HER3 immunoconjugates, and targeting HER3 warrants clinical evaluation in prospective trials., (©2021 The Authors; Published by the American Association for Cancer Research.)

PARP inhibitors are approved for treating advanced prostate cancers (APC) with various defective DNA repair genes; however, further studies to clinically qualify predictive biomarkers are warranted. Herein we analyzed TOPARP-B phase II clinical trial samples, evaluating whole-exome and low-pass whole-genome sequencing and IHC and IF assays evaluating ATM and RAD51 foci (testing homologous recombination repair function). BRCA1/2 germline and somatic pathogenic mutations associated with similar benefit from olaparib; greater benefit was observed with homozygous BRCA2 deletion. Biallelic, but not monoallelic, PALB2 deleterious alterations were associated with clinical benefit. In the ATM cohort, loss of ATM protein by IHC was associated with a better outcome. RAD51 foci loss identified tumors with biallelic BRCA and PALB2 alterations while most ATM - and CDK12 -altered APCs had higher RAD51 foci levels. Overall, APCs with homozygous BRCA2 deletion are exceptional responders; PALB2 biallelic loss and loss of ATM IHC expression associated with clinical benefit. SIGNIFICANCE: Not all APCs with DNA repair defects derive similar benefit from PARP inhibition. Most benefit was seen among patients with BRCA2 homozygous deletions, biallelic loss of PALB2 , and loss of ATM protein. Loss of RAD51 foci, evaluating homologous recombination repair function, was found primarily in tumors with biallelic BRCA1/2 and PALB2 alterations. This article is highlighted in the In This Issue feature, p. 2659 ., (©2021 The Authors; Published by the American Association for Cancer Research.)

Background: Better blood tests to elucidate the behaviour of metastatic castration-resistant prostate cancer (mCRPC) are urgently needed to drive therapeutic decisions. Plasma cell-free DNA (cfDNA) comprises normal and circulating tumour DNA (ctDNA). Low-pass whole-genome sequencing (lpWGS) of ctDNA can provide information on mCRPC behaviour., Objective: To validate and clinically qualify plasma lpWGS for mCRPC., Design, Setting, and Participants: Plasma lpWGS data were obtained for mCRPC patients consenting to optional substudies of two prospective phase 3 trials (FIRSTANA and PROSELICA). In FIRSTANA, chemotherapy-naïve patients were randomised to treatment with docetaxel (75 mg/m 2 ) or cabazitaxel (20 or 25 mg/m 2 ). In PROSELICA, patients previously treated with docetaxel were randomised to 20 or 25 mg/m 2 cabazitaxel. lpWGS data were generated from 540 samples from 188 mCRPC patients acquired at four different time points (screening, cycle 1, cycle 4, and end of study). OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: lpWGS data for ctDNA were evaluated for prognostic, response, and tumour genomic measures. Associations with response and survival data were determined for tumour fraction. Genomic biomarkers including large-scale transition (LST) scores were explored in the context of prior treatments., Results and Limitations: Plasma tumour fraction was prognostic for overall survival in univariable and stratified multivariable analyses (hazard ratio 1.75, 95% confidence interval 1.08-2.85; p = 0.024) and offered added value compared to existing biomarkers (C index 0.722 vs 0.709; p = 0.021). Longitudinal changes were associated with drug response. PROSELICA samples were enriched for LSTs (p = 0.029) indicating genomic instability, and this enrichment was associated with prior abiraterone and enzalutamide treatment but not taxane or radiation therapy. Higher LSTs were correlated with losses of RB1/RNASEH2B, independent of BRCA2 loss., Conclusions: Plasma lpWGS of ctDNA describes CRPC behaviour, providing prognostic and response data of clinical relevance. The added prognostic value of the ctDNA fraction over established biomarkers should be studied further., Patient Summary: We studied tumour DNA in blood samples from patients with prostate cancer. We found that levels of tumour DNA in blood were indicative of disease prognosis, and that changes after treatment could be detected. We also observed a "genetic scar" in the results that was associated with certain previous treatments. This test allows an assessment of tumour activity that can complement existing tests, offer insights into drug response, and detect clinically relevant genetic changes., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Deleterious ATM alterations are found in metastatic prostate cancer (PC); PARP inhibition has antitumour activity against this subset, but only some ATM loss PCs respond., Objective: To characterise ATM-deficient lethal PC and to study synthetic lethal therapeutic strategies for this subset., Design, Setting, and Participants: We studied advanced PC biopsies using validated immunohistochemical (IHC) and next-generation sequencing (NGS) assays. In vitro cell line models modified using CRISPR-Cas9 to impair ATM function were generated and used in drug-sensitivity and functional assays, with validation in a patient-derived model., Outcome Measurements and Statistical Analysis: ATM expression by IHC was correlated with clinical outcome using Kaplan-Meier curves and log-rank test; sensitivity to different drug combinations was assessed in the preclinical models., Results and Limitations: Overall, we detected ATM IHC loss in 68/631 (11%) PC patients in at least one biopsy, with synchronous and metachronous intrapatient heterogeneity; 46/71 (65%) biopsies with ATM loss had ATM mutations or deletions by NGS. ATM IHC loss was not associated with worse outcome from advanced disease, but ATM loss was associated with increased genomic instability (NtAI:number of subchromosomal regions with allelic imbalance extending to the telomere, p = 0.005; large-scale transitions, p = 0.05). In vitro, ATM loss PC models were sensitive to ATR inhibition, but had variable sensitivity to PARP inhibition; superior antitumour activity was seen with combined PARP and ATR inhibition in these models., Conclusions: ATM loss in PC is not always detected by targeted NGS, associates with genomic instability, and is most sensitive to combined ATR and PARP inhibition., Patient Summary: Of aggressive prostate cancers, 10% lose the DNA repair gene ATM; this loss may identify a distinct prostate cancer subtype that is most sensitive to the combination of oral drugs targeting PARP and ATR., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

Purpose: Cyclin-dependent kinase 12 (CDK12) aberrations have been reported as a biomarker of response to immunotherapy for metastatic castration-resistant prostate cancer (mCRPC). Herein, we characterize CDK12-mutated mCRPC, presenting clinical, genomic, and tumor-infiltrating lymphocyte (TIL) data., Experimental Design: Patients with mCRPC consented to the molecular analyses of diagnostic and mCRPC biopsies. Genomic analyses involved targeted next-generation (MiSeq; Illumina) and exome sequencing (NovaSeq; Illumina). TILs were assessed by validated immunocytochemistry coupled with deep learning-based artificial intelligence analyses including multiplex immunofluorescence assays for CD4, CD8, and FOXP3 evaluating TIL subsets. The control group comprised a randomly selected mCRPC cohort with sequencing and clinical data available., Results: Biopsies from 913 patients underwent targeted sequencing between February 2015 and October 2019. Forty-three patients (4.7%) had tumors with CDK12 alterations. CDK12-altered cancers had distinctive features, with some revealing high chromosomal break numbers in exome sequencing. Biallelic CDK12-aberrant mCRPCs had shorter overall survival from diagnosis than controls [5.1 years (95% confidence interval (CI), 4.0-7.9) vs. 6.4 years (95% CI, 5.7-7.8); hazard ratio (HR), 1.65 (95% CI, 1.07-2.53); P = 0.02]. Median intratumoral CD3 + cell density was higher in CDK12 cancers, although this was not statistically significant (203.7 vs. 86.7 cells/mm 2 ; P = 0.07). This infiltrate primarily comprised of CD4 + FOXP3 - cells (50.5 vs. 6.2 cells/mm 2 ; P < 0.0001), where high counts tended to be associated with worse survival from diagnosis (HR, 1.64; 95% CI, 0.95-2.84; P = 0.077) in the overall population., Conclusions: CDK12-altered mCRPCs have worse prognosis, with these tumors surprisingly being primarily enriched for CD4 + FOXP3 - cells that seem to associate with worse outcome and may be immunosuppressive. See related commentary by Lotan and Antonarakis, p. 380 ., (©2020 American Association for Cancer Research.)

Early-phase cancer clinical trials are becoming increasingly accessible for patients with advanced cancer who have exhausted standard treatment options and later phase trial options. Many of these trials mandate research tissue biopsies. Research biopsies have been perceived as ethically fraught due to the perception of potential coercion of vulnerable human subjects. We performed an audit of two years of practice to assess the safety of ultrasound (US)-guided research biopsies, and to look at the yield of a simultaneous tumour next-generation sequencing (NGS) and immunohistochemistry (IHC) molecular characterisation programme. We show that in our institution, US-guided research biopsies were safe, produced adequate tumour content and in a selected subset who underwent in-house NGS sequencing, showed a high rate of actionable mutations with 30% having a Tier 1 variant. Nevertheless, these research biopsies may only provide direct benefit for a minority of patients and we conclude with a reflection on the importance of obtaining truly informed consent., (Copyright © 2021. Published by Elsevier Ltd.)

Purpose: Prostate cancer is the second leading cause of male cancer deaths. Castration-resistant prostate cancer (CRPC) is a lethal stage of the disease that emerges when endocrine therapies are no longer effective at suppressing activity of the androgen receptor (AR) transcription factor. The purpose of this study was to identify genomic mechanisms that contribute to the development and progression of CRPC., Experimental Design: We used whole-genome and targeted DNA-sequencing approaches to identify mechanisms underlying CRPC in an aggregate cohort of 272 prostate cancer patients. We analyzed structural rearrangements at the genome-wide level and carried out a detailed structural rearrangement analysis of the AR locus. We used genome engineering to perform experimental modeling of AR gene rearrangements and long-read RNA sequencing to analyze effects on expression of AR and truncated AR variants (AR-V)., Results: AR was among the most frequently rearranged genes in CRPC tumors. AR gene rearrangements promoted expression of diverse AR-V species. AR gene rearrangements occurring in the context of AR amplification correlated with AR overexpression. Cell lines with experimentally derived AR gene rearrangements displayed high expression of tumor-specific AR-Vs and were resistant to endocrine therapies, including the AR antagonist enzalutamide., Conclusions: AR gene rearrangements are an important mechanism of resistance to endocrine therapies in CRPC., (©2020 American Association for Cancer Research.)

The genomics of primary prostate cancer differ from those of metastatic castration-resistant prostate cancer (mCRPC). We studied genomic aberrations in primary prostate cancer biopsies from patients who developed mCRPC, also studying matching, same-patient, diagnostic, and mCRPC biopsies following treatment. We profiled 470 treatment-naive prostate cancer diagnostic biopsies and, for 61 cases, mCRPC biopsies, using targeted and low-pass whole-genome sequencing (n = 52). Descriptive statistics were used to summarize mutation and copy number profile. Prevalence was compared using Fisher's exact test. Survival correlations were studied using log-rank test. TP53 (27%) and PTEN (12%) and DDR gene defects (BRCA2 7%; CDK12 5%; ATM 4%) were commonly detected. TP53, BRCA2, and CDK12 mutations were markedly more common than described in the TCGA cohort. Patients with RB1 loss in the primary tumor had a worse prognosis. Among 61 men with matched hormone-naive and mCRPC biopsies, differences were identified in AR, TP53, RB1, and PI3K/AKT mutational status between same-patient samples. In conclusion, the genomics of diagnostic prostatic biopsies acquired from men who develop mCRPC differ from those of the nonlethal primary prostatic cancers. RB1/TP53/AR aberrations are enriched in later stages, but the prevalence of DDR defects in diagnostic samples is similar to mCRPC.

Background: This case represents an exceptional response to pembrolizumab in a patient with epithelioid mesothelioma with a further response on rechallenge., Case Presentation: A 77-year-old woman with advanced epithelioid mesothelioma extensively pretreated with chemotherapy demonstrated a prolonged response of 45 months to 52 cycles of pembrolizumab. On rechallenge with pembrolizumab, further disease stability was achieved. Serial biopsies and analysis by immunohistochemistry and immunofluorescence demonstrated marked immune infiltration and documented the emergency of markers of immune exhaustion. Whole exome sequencing demonstrated a reduction in tumor mutational burden consistent with subclone elimination by immune checkpoint inhibitor (CPI) therapy. The relapse biopsy had missense mutation in BTN2A1., Conclusion: This case supports rechallenge of programme death receptor 1 inhibitor in cases of previous CPI sensitivity and gives molecular insights., Competing Interests: Competing interests: AM: honoraria from FARON and Bayer. AW: advisory boards for Bayer, Bristol-Myers Sqibb and Celgene. SP: honoraria from Boehringer Ingelheim, AstraZeneca, Roche, Takeda and Chugai Pharma; advisory boards from Boehringer Ingelheim, AstraZeneca, Roche, Novartis, Pfizer, Bristol-Myer Squibb, MSD, Guardant Health, Abbvie, EMD Serono and Takeda; expenses from Boehringer Ingelheim, Bristol-Myer Squibb and Merck Sharp & Dohme. MO: advisory boards for MSD, Abbvie, BMS, BI, Pierre Fabre. UB: honoraria from Astellas, Novartis, Karus Therapeutics, Phoenix Solutions, Eli Lilly, Astex and Vernalis; funding for phase I investigator-initiated trials from Onyx Pharmaceuticals, BTG International, Chugai, Astrazeneca and Verastem. JdB: personal fees and non-financial support from Astellas Pharma, Genentech/Roche, Pfizer, Sanofi, Bayer, Boehringer Ingelheim, Merck Serono and Merck Sharp & Dohme; grants, personal fees and non-financial support from AstraZeneca; non-financial support from Genmab, GlaxoSmithKline, Orion Pharma GmbH, Qiagen, Taiho Pharmaceutical and Vertex. In addition, JdB has a patent Abiraterone Rewards to Inventors with royalties paid to institution, no personal income and a patent PARP inhibitors and DNA repair defects with royalties paid to institution, no personal income. JL: research funding from Roche Genentech, Genmab and Basilea Travel from Basilea., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Metastatic castration-resistant prostate cancer is enriched in DNA damage response (DDR) gene aberrations. The TOPARP-B trial aims to prospectively validate the association between DDR gene aberrations and response to olaparib in metastatic castration-resistant prostate cancer., Methods: In this open-label, investigator-initiated, randomised phase 2 trial following a selection (or pick-the-winner) design, we recruited participants from 17 UK hospitals. Men aged 18 years or older with progressing metastatic castration-resistant prostate cancer previously treated with one or two taxane chemotherapy regimens and with an Eastern Cooperative Oncology Group performance status of 2 or less had tumour biopsies tested with targeted sequencing. Patients with DDR gene aberrations were randomly assigned (1:1) by a computer-generated minimisation method, with balancing for circulating tumour cell count at screening, to receive 400 mg or 300 mg olaparib twice daily, given continuously in 4-week cycles until disease progression or unacceptable toxicity. Neither participants nor investigators were masked to dose allocation. The primary endpoint of confirmed response was defined as a composite of all patients presenting with any of the following outcomes: radiological objective response (as assessed by Response Evaluation Criteria in Solid Tumors 1.1), a decrease in prostate-specific antigen (PSA) of 50% or more (PSA50) from baseline, or conversion of circulating tumour cell count (from ≥5 cells per 7·5 mL blood at baseline to <5 cells per 7·5 mL blood). A confirmed response in a consecutive assessment after at least 4 weeks was required for each component. The primary analysis was done in the evaluable population. If at least 19 (43%) of 44 evaluable patients in a dose cohort responded, then the dose cohort would be considered successful. Safety was assessed in all patients who received at least one dose of olaparib. This trial is registered at ClinicalTrials.gov, NCT01682772. Recruitment for the trial has completed and follow-up is ongoing., Findings: 711 patients consented for targeted screening between April 1, 2015, and Aug 30, 2018. 161 patients had DDR gene aberrations, 98 of whom were randomly assigned and treated (49 patients for each olaparib dose), with 92 evaluable for the primary endpoint (46 patients for each olaparib dose). Median follow-up was 24·8 months (IQR 16·7-35·9). Confirmed composite response was achieved in 25 (54·3%; 95% CI 39·0-69·1) of 46 evaluable patients in the 400 mg cohort, and 18 (39·1%; 25·1-54·6) of 46 evaluable patients in the 300 mg cohort. Radiological response was achieved in eight (24·2%; 11·1-42·3) of 33 evaluable patients in the 400 mg cohort and six (16·2%; 6·2-32·0) of 37 in the 300 mg cohort; PSA50 response was achieved in 17 (37·0%; 23·2-52·5) of 46 and 13 (30·2%; 17·2-46·1) of 43; and circulating tumour cell count conversion was achieved in 15 (53·6%; 33·9-72·5) of 28 and 13 (48·1%; 28·7-68·1) of 27. The most common grade 3-4 adverse event in both cohorts was anaemia (15 [31%] of 49 patients in the 300 mg cohort and 18 [37%] of 49 in the 400 mg cohort). 19 serious adverse reactions were reported in 13 patients. One death possibly related to treatment (myocardial infarction) occurred after 11 days of treatment in the 300 mg cohort., Interpretation: Olaparib has antitumour activity against metastatic castration-resistant prostate cancer with DDR gene aberrations, supporting the implementation of genomic stratification of metastatic castration-resistant prostate cancer in clinical practice., Funding: Cancer Research UK, AstraZeneca, Prostate Cancer UK, the Prostate Cancer Foundation, the Experimental Cancer Medicine Centres Network, and the National Institute for Health Research Biomedical Research Centres., (Copyright © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Background: Detection of androgen receptor splice variant-7 (AR-V7) mRNA in circulating tumour cells (CTCs) is associated with worse outcome in metastatic castration-resistant prostate cancer (mCRPC). However, studies rarely report comparisons with CTC counts and biopsy AR-V7 protein expression., Objective: To determine the reproducibility of AdnaTest CTC AR-V7 testing, and associations with clinical characteristics, CellSearch CTC counts, tumour biopsy AR-V7 protein expression and overall survival (OS)., Design, Setting, and Participants: CTC AR-V7 status was determined for 227 peripheral blood samples, from 181 mCRPC patients with CTC counts (202 samples; 136 patients) and matched mCRPC biopsies (65 samples; 58 patients)., Outcome Measurements and Statistical Analysis: CTC AR-V7 status was associated with clinical characteristics, CTC counts, and tissue biopsy AR-V7 protein expression. The association of CTC AR-V7 status and other baseline variables with OS was determined., Results and Limitations: Of the samples, 35% were CTC+/AR-V7+. CTC+/AR-V7+ samples had higher CellSearch CTC counts (median CTC; interquartile range [IQR]: 60, 19-184 vs 9, 2-64; Mann-Whitney test p<0.001) and biopsy AR-V7 protein expression (median H-score, IQR: 100, 63-148 vs 15, 0-113; Mann-Whitney test p=0.004) than CTC+/AR-V7- samples. However, both CTC- (63%) and CTC+/AR-V7- (62%) patients had detectable AR-V7 protein in contemporaneous biopsies. After accounting for baseline characteristics, there was shorter OS in CTC+/AR-V7+ patients than in CTC- patients (hazard ratio [HR] 2.13; 95% confidence interval [CI] 1.23-3.71; p=0.02); surprisingly, there was no evidence that CTC+/AR-V7+ patients had worse OS than CTC+/AR-V7- patients (HR 1.26; 95% CI 0.73-2.17; p=0.4). A limitation of this study was the heterogeneity of treatment received., Conclusions: Studies reporting the prognostic relevance of CTC AR-V7 status must account for CTC counts. Discordant CTC AR-V7 results and AR-V7 protein expression in matched, same-patient biopsies are reported., Patient Summary: Liquid biopsies that determine circulating tumour cell androgen receptor splice variant-7 status have the potential to impact treatment decisions in metastatic castration-resistant prostate cancer patients. Robust clinical qualification of these assays is required before their routine use., (Copyright © 2019 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Prostate-specific membrane antigen (PSMA; folate hydrolase) prostate cancer (PC) expression has theranostic utility., Objective: To elucidate PC PSMA expression and associate this with defective DNA damage repair (DDR)., Design, Setting, and Participants: Membranous PSMA (mPSMA) expression was scored immunohistochemically from metastatic castration-resistant PC (mCRPC) and matching, same-patient, diagnostic biopsies, and correlated with next-generation sequencing (NGS) and clinical outcome data., Outcome Measurements and Statistical Analysis: Expression of mPSMA was quantitated by modified H-score. Patient DNA was tested by NGS. Gene expression and activity scores were determined from mCRPC transcriptomes. Statistical correlations utilised Wilcoxon signed rank tests, survival was estimated by Kaplan-Meier test, and sample heterogeneity was quantified by Shannon's diversity index., Results and Limitations: Expression of mPSMA at diagnosis was associated with higher Gleason grade (p=0.04) and worse overall survival (p=0.006). Overall, mPSMA expression levels increased at mCRPC (median H-score [interquartile range]: castration-sensitive prostate cancer [CSPC] 17.5 [0.0-60.0] vs mCRPC 55.0 [2.8-117.5]). Surprisingly, 42% (n=16) of CSPC and 27% (n=16) of mCRPC tissues sampled had no detectable mPSMA (H-score <10). Marked intratumour heterogeneity of mPSMA expression, with foci containing no detectable PSMA, was observed in all mPSMA expressing CSPC (100%) and 37 (84%) mCRPC biopsies. Heterogeneous intrapatient mPSMA expression between metastases was also observed, with the lowest expression in liver metastases. Tumours with DDR had higher mPSMA expression (p=0.016; 87.5 [25.0-247.5] vs 20 [0.3-98.8]; difference in medians 60 [5.0-95.0]); validation cohort studies confirmed higher mPSMA expression in patients with deleterious aberrations in BRCA2 (p<0.001; median H-score: 300 [165-300]; difference in medians 195.0 [100.0-270.0]) and ATM (p=0.005; 212.5 [136.3-300]; difference in medians 140.0 [55.0-200]) than in molecularly unselected mCRPC biopsies (55.0 [2.75-117.5]). Validation studies using mCRPC transcriptomes corroborated these findings, also indicating that SOX2 high tumours have low PSMA expression., Conclusions: Membranous PSMA expression is upregulated in some but not all PCs, with mPSMA expression demonstrating marked inter- and intrapatient heterogeneity. DDR aberrations are associated with higher mPSMA expression and merit further evaluation as predictive biomarkers of response for PSMA-targeted therapies in larger, prospective cohorts., Patient Summary: Through analysis of prostate cancer samples, we report that the presence of prostate-specific membrane antigen (PSMA) is extremely variable both within one patient and between different patients. This may limit the usefulness of PSMA scans and PSMA-targeted therapies. We show for the first time that prostate cancers with defective DNA repair produce more PSMA and so may respond better to PSMA-targeting treatments., (Copyright © 2019 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Liquid biopsies have demonstrated that the constitutively active androgen receptor splice variant-7 (AR-V7) associates with reduced response and overall survival from endocrine therapies in castration-resistant prostate cancer (CRPC). However, these studies provide little information pertaining to AR-V7 expression in prostate cancer (PC) tissue., Methods: Following generation and validation of a potentially novel AR-V7 antibody for IHC, AR-V7 protein expression was determined for 358 primary prostate samples and 293 metastatic biopsies. Associations with disease progression, full-length androgen receptor (AR-FL) expression, response to therapy, and gene expression were determined., Results: We demonstrated that AR-V7 protein is rarely expressed (<1%) in primary PC but is frequently detected (75% of cases) following androgen deprivation therapy, with further significant (P = 0.020) increase in expression following abiraterone acetate or enzalutamide therapy. In CRPC, AR-V7 expression is predominantly (94% of cases) nuclear and correlates with AR-FL expression (P ≤ 0.001) and AR copy number (P = 0.026). However, dissociation of expression was observed, suggesting that mRNA splicing remains crucial for AR-V7 generation. AR-V7 expression was heterogeneous between different metastases from a patient, although AR-V7 expression was similar within a metastasis. Moreover, AR-V7 expression correlated with a unique 59-gene signature in CRPC, including HOXB13, a critical coregulator of AR-V7 function. Finally, AR-V7-negative disease associated with better prostate-specific antigen (PSA) responses (100% vs. 54%, P = 0.03) and overall survival (74.3 vs. 25.2 months, hazard ratio 0.23 [0.07-0.79], P = 0.02) from endocrine therapies (pre-chemotherapy)., Conclusion: This study provides impetus to develop therapies that abrogate AR-V7 signaling to improve our understanding of AR-V7 biology and to confirm the clinical significance of AR-V7., Funding: Work at the University of Washington and in the Plymate and Nelson laboratories is supported by the Department of Defense Prostate Cancer Research Program (W81XWH-14-2-0183, W81XWH-12-PCRP-TIA, W81XWH-15-1-0430, and W81XWH-13-2-0070), the Pacific Northwest Prostate Cancer SPORE (P50CA97186), the Institute for Prostate Cancer Research, the Veterans Affairs Research Program, the NIH/National Cancer Institute (P01CA163227), and the Prostate Cancer Foundation. Work in the de Bono laboratory was supported by funding from the Movember Foundation/Prostate Cancer UK (CEO13-2-002), the US Department of Defense (W81XWH-13-2-0093), the Prostate Cancer Foundation (20131017 and 20131017-1), Stand Up To Cancer (SU2C-AACR-DT0712), Cancer Research UK (CRM108X-A25144), and the UK Department of Health through an Experimental Cancer Medicine Centre grant (ECMC-CRM064X).

Background: Loss of ataxia telangiectasia mutated (ATM), a key protein regulating DNA repair signaling, has been suggested to increase sensitivity to DNA damaging agents. We conducted a study analyzing the loss of ATM protein expression in colorectal cancer and correlated this with clinical outcomes., Materials and Methods: The clinical outcomes data and tumor samples from metastatic colorectal cancer patients referred to the Royal Marsden Hospital Drug Development Unit (United Kingdom) from 2012 to 2016 and providing consent for a molecular characterization study were analyzed. Immunohistochemistry (IHC) slides were assessed by a pathologist for nuclear staining intensity of ATM and semiquantitatively scored. ATM loss was defined as a nuclear H-score of ≤ 10., Results: Of 223 colorectal cancer samples, ATM IHC loss was identified in 17 (8%). ATM loss was independent of the RAS and RAF mutational status. ATM loss was associated with superior overall survival after first-line oxaliplatin-based therapy (49 vs. 32 months; hazard ratio [HR], 2.52) but not with irinotecan-based therapy (24 vs. 33 months; HR, 0.72). ATM loss was not prognostic for survival from the diagnosis (50 vs. 44 months; HR, 1.43)., Conclusion: ATM could be considered a biomarker for the development of novel DNA repair targeting agents and treatment of colorectal cancer., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

Purpose: Circulating tumor cells (CTCs) have clinical relevance, but their study has been limited by their low frequency. Experimental Design: We evaluated liquid biopsies by apheresis to increase CTC yield from patients suffering from metastatic prostate cancer, allow precise gene copy-number calls, and study disease heterogeneity. Results: Apheresis was well tolerated and allowed the separation of large numbers of CTCs; the average CTC yield from 7.5 mL of peripheral blood was 167 CTCs, whereas the average CTC yield per apheresis (mean volume: 59.5 mL) was 12,546 CTCs. Purified single CTCs could be isolated from apheresis product by FACS sorting; copy-number aberration (CNA) profiles of 185 single CTCs from 14 patients revealed the genomic landscape of lethal prostate cancer and identified complex intrapatient, intercell, genomic heterogeneity missed on bulk biopsy analyses. Conclusions: Apheresis facilitated the capture of large numbers of CTCs noninvasively with minimal morbidity and allowed the deconvolution of intrapatient heterogeneity and clonal evolution. Clin Cancer Res; 24(22); 5635-44. ©2018 AACR ., (©2018 American Association for Cancer Research.)

Purpose: CHD1 deletions and SPOP mutations frequently cooccur in prostate cancer with lower frequencies reported in castration-resistant prostate cancer (CRPC). We monitored CHD1 expression during disease progression and assessed the molecular and clinical characteristics of CHD1 -deleted/ SPOP -mutated metastatic CRPC (mCRPC). Experimental Design: We identified 89 patients with mCRPC who had hormone-naive and castration-resistant tumor samples available: These were analyzed for CHD1, PTEN, and ERG expression by IHC. SPOP status was determined by targeted next-generation sequencing (NGS). We studied the correlations between these biomarkers and (i) overall survival from diagnosis; (ii) overall survival from CRPC; (iii) duration of abiraterone treatment; and (iv) response to abiraterone. Relationship with outcome was analyzed using Cox regression and log-rank analyses. Results: CHD1 protein loss was detected in 11 (15%) and 13 (17%) of hormone-sensitive prostate cancer (HSPC) and CRPC biopsies, respectively. Comparison of CHD1 expression was feasible in 56 matched, same patient HSPC and CRPC biopsies. CHD1 protein status in HSPC and CRPC correlated in 55 of 56 cases (98%). We identified 22 patients with somatic SPOP mutations, with six of these mutations not reported previously in prostate cancer. SPOP mutations and/or CHD1 loss was associated with a higher response rate to abiraterone (SPOP: OR, 14.50 P = 0.001; CHD1: OR, 7.30, P = 0.08) and a longer time on abiraterone (SPOP: HR, 0.37, P = 0.002, CHD1: HR, 0.50, P = 0.06). Conclusions: SPOP -mutated mCRPCs are strongly enriched for CHD1 loss. These tumors appear highly sensitive to abiraterone treatment. Clin Cancer Res; 24(22); 5585-93. ©2018 AACR ., (©2018 American Association for Cancer Research.)

Background: Understanding the integrated immunogenomic landscape of advanced prostate cancer (APC) could impact stratified treatment selection., Methods: Defective mismatch repair (dMMR) status was determined by either loss of mismatch repair protein expression on IHC or microsatellite instability (MSI) by PCR in 127 APC biopsies from 124 patients (Royal Marsden [RMH] cohort); MSI by targeted panel next-generation sequencing (MSINGS) was then evaluated in the same cohort and in 254 APC samples from the Stand Up To Cancer/Prostate Cancer Foundation (SU2C/PCF). Whole exome sequencing (WES) data from this latter cohort were analyzed for pathogenic MMR gene variants, mutational load, and mutational signatures. Transcriptomic data, available for 168 samples, was also performed., Results: Overall, 8.1% of patients in the RMH cohort had some evidence of dMMR, which associated with decreased overall survival. Higher MSINGS scores associated with dMMR, and these APCs were enriched for higher T cell infiltration and PD-L1 protein expression. Exome MSINGS scores strongly correlated with targeted panel MSINGS scores (r = 0.73, P < 0.0001), and higher MSINGS scores associated with dMMR mutational signatures in APC exomes. dMMR mutational signatures also associated with MMR gene mutations and increased immune cell, immune checkpoint, and T cell-associated transcripts. APC with dMMR mutational signatures overexpressed a variety of immune transcripts, including CD200R1, BTLA, PD-L1, PD-L2, ADORA2A, PIK3CG, and TIGIT., Conclusion: These data could impact immune target selection, combination therapeutic strategy selection, and selection of predictive biomarkers for immunotherapy in APC., Funding: We acknowledge funding support from Movember, Prostate Cancer UK, The Prostate Cancer Foundation, SU2C, and Cancer Research UK.

Background: Germline DNA damage repair gene mutation (gDDRm) is found in >10% of metastatic prostate cancer (mPC). Their prognostic and predictive impact relating to standard therapies is unclear., Objective: To determine whether gDDRm status impacts benefit from established therapies in mPC., Design, Setting, and Participants: This is a retrospective, international, observational study. Medical records were reviewed for 390 mPC patients with known gDDRm status. All 372 patients from Royal Marsden (UK), Weill-Cornell (NY), and University of Washington (WA) were previously included in a prevalence study (Pritchard, NEJM 2016); the remaining 18 were gBRCA1/2m carriers, from the kConFab consortium, Australia., Outcome Measurements and Statistical Analysis: Response rate (RR), progression-free survival (PFS), and overall survival (OS) data were collected. To account for potential differences between cohorts, a mixed-effect model (Weibull distribution) with random intercept per cohort was used., Results and Limitations: The gDDRm status was known for all 390 patients (60 carriers of gDDRm [gDDRm+], including 37 gBRCA2m, and 330 cases not found to carry gDDRm [gDDRm-]); 74% and 69% were treated with docetaxel and abiraterone/enzalutamide, respectively, and 36% received PARP inhibitors (PARPi) and/or platinum. Median OS from castration resistance was similar among groups (3.2 vs 3.0 yr, p=0.73). Median docetaxel PFS for gDDRm+ (6.8 mo) was not significantly different from that for gDDRm- (5.1 mo), and RRs were similar (gDDRm+=61%; gDDRm-=54%). There were no significant differences in median PFS and RR on first-line abiraterone/enzalutamide (gDDRm+=8.3 mo, gDDRm-=8.3 mo; gDDRm+=46%, gDDRm-=56%). Interaction test for PARPi/platinum and gDDRm+ resulted in an OS adjusted hazard ratio of 0.59 (95% confidence interval 0.28-1.25; p=0.17). Results are limited by the retrospective nature of the analysis., Conclusions: mPC patients with gDDRm appeared to benefit from standard therapies similarly to the overall population; prospective studies are ongoing to investigate the impact of PARPi/platinum., Patient Summary: Patients with inherited DNA repair mutations benefit from standard therapies similarly to other metastatic prostate cancer patients., (Copyright © 2018 European Association of Urology. Published by Elsevier B.V. All rights reserved.)

Purpose: Precise detection of copy number aberrations (CNA) from tumor biopsies is critically important to the treatment of metastatic prostate cancer. The use of targeted panel next-generation sequencing (NGS) is inexpensive, high throughput, and easily feasible, allowing single-nucleotide variant calls, but CNA estimation from this remains challenging. Experimental Design: We evaluated CNVkit for CNA identification from amplicon-based targeted NGS in a cohort of 110 fresh castration-resistant prostate cancer biopsies and used capture-based whole-exome sequencing (WES), array comparative genomic hybridization (aCGH), and FISH to explore the viability of this approach. Results: We showed that this method produced highly reproducible CNA results ( r = 0.92), with the use of pooled germline DNA as a coverage reference supporting precise CNA estimation. CNA estimates from targeted NGS were comparable with WES ( r = 0.86) and aCGH ( r = 0.7); for key selected genes ( BRCA2, MYC, PIK3CA, PTEN , and RB1 ), CNA estimation correlated well with WES ( r = 0.91) and aCGH ( r = 0.84) results. The frequency of CNAs in our population was comparable with that previously described (i.e., deep deletions: BRCA2 4.5%; RB1 8.2%; PTEN 15.5%; amplification: AR 45.5%; gain: MYC 31.8%). We also showed, utilizing FISH, that CNA estimation can be impacted by intratumor heterogeneity and demonstrated that tumor microdissection allows NGS to provide more precise CNA estimates. Conclusions: Targeted NGS and CNVkit-based analyses provide a robust, precise, high-throughput, and cost-effective method for CNA estimation for the delivery of more precise patient care. Clin Cancer Res; 23(20); 6070-7. ©2017 AACR ., (©2017 American Association for Cancer Research.)

Biomarkers for more precise patient care are needed in metastatic prostate cancer. We have reported a phase II trial (TOPARP-A) of the PARP inhibitor olaparib in metastatic prostate cancer, demonstrating antitumor activity associating with homologous recombination DNA repair defects. We now report targeted and whole-exome sequencing of serial circulating cell-free DNA (cfDNA) samples collected during this trial. Decreases in cfDNA concentration independently associated with outcome in multivariable analyses (HR for overall survival at week 8: 0.19; 95% CI, 0.06-0.56; P = 0.003). All tumor tissue somatic DNA repair mutations were detectable in cfDNA; allele frequency of somatic mutations decreased selectively in responding patients (χ 2 P < 0.001). At disease progression, following response to olaparib, multiple subclonal aberrations reverting germline and somatic DNA repair mutations ( BRCA2, PALB2 ) back in frame emerged as mechanisms of resistance. These data support the role of liquid biopsies as a predictive, prognostic, response, and resistance biomarker in metastatic prostate cancer. Significance: We report prospectively planned, serial, cfDNA analyses from patients with metastatic prostate cancer treated on an investigator-initiated phase II trial of olaparib. These analyses provide predictive, prognostic, response, and resistance data with "second hit" mutations first detectable at disease progression, suggesting clonal evolution from treatment-selective pressure and platinum resistance. Cancer Discov; 7(9); 1006-17. ©2017 AACR. See related commentary by Domchek, p. 937 See related article by Kondrashova et al., p. 984 See related article by Quigley et al., p. 999 This article is highlighted in the In This Issue feature, p. 920 ., (©2017 American Association for Cancer Research.)

Aims and Background: Lynch syndrome (LS) is clinically defined by the Amsterdam criteria (AC) and by germline mutations in mismatch-repair (MMR) genes leading to microsatellite instability (MSI) at the molecular level. Patients who do not fulfil AC are considered suspected-Lynch according to the less stringent Bethesda guidelines (BG) and should be tested for MSI and MMR germline mutations. BRAF mutations have been proposed as a marker to exclude LS because they are generally absent in LS patients and present in sporadic colorectal cancer (sCRC) with MSI due to promoter hypermethylation of the MLH1 gene. Our aim was to verify whether BRAF mutations may improve the criteria to select patients for germline MMR mutation assessment., Material and Methods: We analyzed 303 formalin-fixed paraffin-embedded CRC samples including 174 sCRC, 28 patients fulfilling AC, and 101 suspected-Lynch patients fulfilling BG. We analyzed MSI and BRAF mutations in all CRC samples. MLH1, MSH2 and MSH6 germline mutations were investigated in MSI patients fulfilling AC or BG., Results: sCRC samples showed MSI in 20/174 (11%) cases. BRAF mutations were detected in 10/174 (6%) sCRC cases and were significantly correlated with MSI (P = 0.002). MSI was observed in 24/28 (86%) Amsterdam cases which were BRAF wild-type. MMR gene mutation was detected in 22/26 (85%) AC cases, all showing MSI. Suspected-Lynch cases carried MSI in 41/101 (40%) and BRAF mutations in 7/101 (7%) cases. MMR gene mutation was detected in 13/28 (46%) evaluable MSI patients of this group and only in cases characterized by a wild-type BRAF gene., Conclusions: The prevalence of BRAF mutations in CRC patients is not high but extremely correlated with MSI and risk categories as BG, whereas they are absent in LS patients. BRAF mutation detection can reduce the need for MMR gene analysis in a small (but not negligible) proportion of MSI patients (7%), with a positive impact on the financial and psychological costs of unnecessary tests.

Aims and Background: The quantification and molecular characterization of circulating free DNA (cfDNA) have attracted much interest as new and promising, noninvasive means of detecting and monitoring the presence of surgical resectable colorectal cancer (CRC). Instead, the role of cfDNA in the early detection of malignant and premalignant colorectal lesions is still unclear. The aim of this study was to evaluate the predictive power of the quantification and KRAS status of cfDNA in detecting early colorectal lesions in plasma from healthy high-risk subjects., Methods: The study population consisted of 170 consecutive healthy high-risk subjects aged >50 years who participated in the screening program promoted by the Local Health Service (ASL-Milano) for early CRC detection and who underwent endoscopic examination after being found positive at fecal occult blood test (FOBT). Thirty-four participants had malignant lesions consisting of 12 adenocarcinomas (at an early stage in half of the cases) and 22 instances of high-grade intraepithelial neoplasia (HGIN) in adenomas; 73 participants had premalignant lesions (adenomas and hyperplasia), and 63 participants had no lesions. Plasma cfDNA was quantified by quantitative real-time PCR and analyzed for KRAS mutations by a mutant-enriched PCR. KRAS status was assessed also in matched adenocarcinoma and HGIN tissues. The distribution of cfDNA concentrations among FOBT-positive subjects with diagnosed lesion (cases) was compared with that of FOBT-positive subjects without lesions (controls) and its predictive capability (AUC) was assessed., Results: The predictive capability of cfDNA levels was satisfactory in predicting adenocarcinomas (AUC 0.709; 95% CI, 0.508-0.909) but not HGIN and premalignant lesions. The rate of KRAS mutations in plasma was low (5/170 = 3%) compared with the rate observed in the matched adenocarcinoma and HGIN tissues (45%)., Conclusions: The use of cfDNA quantification to predict adenocarcinoma at an early stage in high-risk (aged >50 years and FOBT positive) subjects seems to be promising but needs more sensitive methods to improve cfDNA detection.

Background: Few data are available outlining outcomes of panitumumab in advanced colorectal cancer patients benefiting from prior cetuximab-based regimens., Patients and Methods: Thirty patients with KRAS wild type metastatic colorectal cancer with clinical benefit from prior cetuximab-based regimens between May 2004 and October 2011 were reviewed at nine Italian Institutions. Inclusion key criteria included interruption of cetuximab for reasons other than progressive disease. Patients were classified according to prior regimens (0 or ≥1), prior response or stabilization, surgery of metastases, and Köhne prognostic score. At the time of subsequent progression, patients were treated with single agent panitumumab until progressive disease, unacceptable toxicity, or consent withdrawal., Results: Panitumumab obtained 67% disease control rate and 30% objective response rate, with median PFS of 4.2 and median OS of 9.6 mo. Patients with BRAF/NRAS/PI3KCA and KRAS (by mutant enriched technique) wild-type tumors had the best chance of response to panitumumab., Conclusions: Single agent panitumumab provided significant clinical benefit in heavily pretreated patients without acquired resistance to prior cetuximab-based regimens.

Altered expression of miRNAs is associated with development and progression of various human cancers by regulating the translation of oncogenes and tumor suppressor genes. In colorectal cancer, these regulators complement the Vogelstein multistep model of pathogenesis and have the potential of becoming a novel class of tumor biomarkers and therapeutic targets. Using quantitative real-time PCR, we measured the expression of 621 mature miRNAs in 40 colorectal cancers and their paired normal tissues and identified 23 significantly deregulated miRNAs. We subsequently evaluated their association with clinical characteristics of the samples and presence of alterations in the molecular markers of colorectal cancer progression. Expression levels of miR-31 were correlated with CA19-9 and miR-18a, miR-21, and miR-31 were associated with mutations in APC gene. To investigate the downstream regulation of the differentially expressed miRNAs identified, we integrated putative mRNA target predictions with the results of a meta-analysis of seven public gene expression datasets of normal and tumor samples of colorectal cancer patients. Many of the colorectal cancer deregulated miRNAs computationally mapped to targets involved in pathways related to progression. Here one promising candidate pair (miR-1 and MET) was studied and functionally validated. We show that miR-1 can have a tumor suppressor function in colorectal cancer by directly downregulating MET oncogene both at RNA and protein level and that reexpression of miR-1 leads to MET-driven reduction of cell proliferation and motility, identifying the miR-1 downmodulation as one of the events that could enhance colorectal cancer progression.

Our aim was to assess the activation profile of EGFR, PDGFRB and PDGFRA receptor tyrosine kinases (RTK) and their downstream effectors in a series of cryopreserved diffuse malignant peritoneal mesothelioma (DMPM) surgical specimens to discover the targets for drug inhibition. We also made a complementary analysis of the cytotoxic effects of some kinase inhibitors on the proliferation of the human peritoneal mesothelioma STO cell line. We found the expression/phosphorylation of EGFR and PDGFRB in most of the tumours, and PDGFRA activation in half. The expression of the cognate ligands TGF-α, PDGFB and PDGFA in the absence of RTK mutation and amplification suggested the presence of an autocrine/paracrine loop. There was also evidence of EGFR and PDGFRB co-activation. RTK downstream signalling analysis demonstrated the activation/expression of ERK1/2, AKT and mTOR, together with S6 and 4EBP1, in almost all the DMPMs. No KRAS/BRAF mutations, PI3KCA mutations/amplifications or PTEN inactivation were observed. Real-time polymerase chain reaction revealed the decreased expression of TSC1 c-DNA in half of the tumours. In vitro cytotoxicity studies showed the STO cell line to be resistant to gefitinib and sensitive to sequential treatment with RAD001 and sorafenib; these findings were consistent with the presence of the KRAS mutation G12D in these cells although it was not detectable in the original tumour. Our results highlight the ligand-dependent activation and co-activation of EGFR and PDGFRB, as well as a connection between these activated RTKs and the downstream mTOR pathway, thus supporting the role of combined treatment with RTK and mTOR inhibitors in DMPM., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The objective was to evaluate the influence of varying plasma progesterone (P(4)) concentrations throughout the luteal phase in dairy cows on PGF(2alpha) production (assessed as plasma concentrations of 13,14-dihydro-15-keto-PGF(2alpha); PGFM) following treatment with estradiol-17beta (E(2)) or oxytocin (OT). In all experiments, time of ovulations was synchronized with the OvSynch protocol and Day 0 corresponded to day of second GnRH injection. In Experiment 1, non-lactating dairy cows on Day 6 remained non-treated (n=9), received 20mg LH (n=7), or had ovarian follicles larger than 6mm aspirated (n=8). In Experiment 2, cows on Day 6 were untreated (n=9) or received 5000 IU hCG (n=10). In Experiments 1 and 2, all cows received 3mg E(2) on Day 17, and blood samples were collected every 30 min from 2h before to 10h after E(2). Experiment 3 was conducted in two periods, each from Days 0 to 17 of the estrous cycle. At the end of Period 1, animals switched treatments in a crossover arrangement. Animals in Group 2/8 (n=4) received 2 kg/d of concentrate in the first period and 8 kg/d in the second period. Animals in Group 8/2 (n=7) received the alternate sequence. Blood was collected daily for measurement of P(4) 4h after concentrate feeding. On Day 17, blood was collected from 1h before to 1h after a 100 IU OT injection. In Experiment 1, both plasma P(4) and release of PGF(2alpha) were similar between LH-treated and control cows (P>0.10). In Experiment 2, plasma P(4) was elevated to a greater extent on Day 17 in cows treated with hCG (P<0.05) and plasma PGFM was also greater in hCG-treated animals (treatment x time interaction; P<0.05). In Experiment 3, there was a group x period interaction (P<0.01) for plasma P(4), indicating that less concentrate feeding was associated with greater plasma P(4). Release of PGF(2alpha) in response to OT was greater for cows receiving less concentrate (group x period interaction; P<0.05). In conclusion, dairy cows with more elevated blood P(4) concentrations released more PGF(2alpha) in response to E(2) or OT.

The canine corpus luteum (CL) typically sustains elevated plasma progesterone concentrations for 2 months or more, with a peak approximately 15-25 days after ovulation, followed by a slow decline. The processes involved in the slow, protracted regression of the CL over the remaining 1.5-2-month period in nonpregnant bitches and until shortly prepartum in pregnant bitches are not well characterized. The rapid luteolysis that occurs immediately prepartum appears to be a result of a prepartum rise in peripheral PGF. The potential role of PGF in the slow regression process in the several weeks preceding parturition and in nonpregnant bitches after 15-25 days after ovulation is not known. Therefore, plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2-alpha (PGFM), progesterone (P4) and estradiol (E2) were determined and compared in bitches during nonpregnant diestrus (n = 9) or pregnancy (n = 8). During the gradual decrease in plasma concentrations of progesterone in both groups, the P4 pattern appeared unrelated to changes in either E2 or PGFM concentrations. The PGFM pattern was different between diestrus and pregnant bitches (P > 0.01); there was an apparent progressive but slow increase in PGFM in pregnant bitches from Days 30 to 60, followed by a large increase prior to parturition; concentrations declined immediately postpartum. However, there were no increases in PGFM during the same interval in nonpregnant bitches. Mean estradiol concentrations were sporadically elevated during the last third of pregnancy and less so in nonpregnant diestrus; there was no acute prepartum increase in estradiol associated with the PGFM increase. In summary, although there were no apparent changes in peripheral PGF2alpha concentration involved in regulating the slow protracted phase of luteal regression in nonpregnant bitches, modest increases in PGFM may play a role in ovarian function after mid-gestation in pregnant bitches. Furthermore, the acute prepartum rise in PGFM was not dependent on any concomitant increase in estradiol concentrations.