Heterogeneity Of Prostate Cancer Research Articles

Abstract 5345: Heterogeneous tumor PSMA expression represents a resistance mechanism to PSMA-targeted radioligand therapy

Abstract Radioligand therapy (RLT) with prostate-specific membrane antigen (PSMA)-targeting ligands is effective in ~50% of patients with advanced prostate cancer (PC). Causes for RLT failure are not well understood. The prevalent PSMA heterogeneity in PC might contribute to RLT failure. Here we investigate the relationship between RLT efficacy and PSMA levels per cell, and PSMA heterogeneity. PC cells expressing different levels of PSMA (RM1-PSMA low, medium, high, or RM1-YFP that do not express PSMA), or a mix of PSMA− and PSMA+ cells (RM1-YFP/ RM1-PSMA-high; PC3/ PC3-PIP) at various ratios were subcutaneously injected into NSG mice. Mice were treated with 177Lu- or 225Ac-PSMA617 (RLT) and tumor growth was monitored. In a subset of mice, radioligand uptake (γ-counting), DNA damage and PSMA expression (anti-53BP1 and -PSMA immunohistochemistry, respectively) were quantified in tumors resected 2 days after RLT. Increasing PSMA levels and fractions of PSMA+ cells improved RLT efficacy in both, the RM1 and PC3 model. PSMA expression correlated with radioligand uptake into the tumor and the degree of DNA damage and. Treatment with 225Ac-PSMA617 (vs. 177Lu-PSMA617) improved RLT outcomes and tended to enhance the differences in therapeutic efficacy between experimental groups. Taken together, we demonstrate in mouse models of PC that optimal anti-tumor efficacy of RLT hinges on homogenously high target expression. Although PSMA-RLT is effective even in tumors with low PSMA levels or with a small number of PSMA+ cells, low or heterogeneous PSMA expression might result in undertreatment and selection of treatment resistant clones. Systematic assessment of intra- and inter-lesion PSMA heterogeneity is currently not feasible clinically; however, this issue might be addressed by individual patient dosimetry to optimize safely delivered maximal tumor doses. Clinical studies designed to determine intra- and inter-lesion PSMA heterogeneity and to optimize PSMA-RLT for each patient are highly warranted. Citation Format: Katharina Lueckerath, Kyle Current, Catherine Meyer, Clara Magyar, Christine E. Mona, Joel Almajano, Roger Slavik, Andreea D. Stuparu, Chloe Cheng, David Dawson, Caius Radu, Johannes Czernin. Heterogeneous tumor PSMA expression represents a resistance mechanism to PSMA-targeted radioligand therapy [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 5345.

Abstract 1316: Molecular features of complete response to neoadjuvant anti-androgen therapy in high risk localized prostate cancer

Abstract Though often curable, high-risk localized prostate cancer has a significant chance of recurring either biochemically, locoregionally, or as distant metastatic disease. Efforts are ongoing to evaluate neoadjuvant strategies to reduce this risk of recurrence. Our recent clinical trial showed that intense androgen deprivation with enzalutamide, leuprolide, and abiraterone acetate with prednisone (ELAP) induced pathologic complete response or minimal residual disease (< 5mm) at prostatectomy in 30% of trial patients (exceptional responders). Though previous studies have identified the pathological and genomic heterogeneity of localized prostate cancer, the impact of this heterogeneity on treatment response is unknown. To address this, we performed multi-region whole-exome and whole transcriptome sequencing on tumor and normal prostate regions from 15 exceptional responders and 15 non-responders treated with intensive androgen deprivation prior to prostatectomy. Overall, we found heterogeneous somatic mutation patterns with strong evidence of intra-tumoral heterogeneity and no association between mutation frequency and response. However, when subsetting patients by treatment response, SPOP mutation and SPOPL copy number loss were only observed in exceptional responders, while TP53 mutations were only observed in the non-responders. We observed expression signature differences between exceptional responders and non-responders, with exceptional responders having an increase in Androgen Receptor related gene signatures. Though underpowered to identify statistically significant genomic correlates of response to neoadjuvant ADT, our findings may inform future studies to identify clinically relevant features of high-risk localized prostate cancers to stratify therapies to reduce the risk of disease recurrence. Citation Format: Alok Tewari, Alexander T. Cheung, Jake Conway, Jihye Park, Stephanie Wankowicz, Rosina T. Lis, Zhenwei Zhang, Saud AlDubayan, Rana R. McKay, Mary-Ellen Taplin, Eliezer M. Van Allen. Molecular features of complete response to neoadjuvant anti-androgen therapy in high risk localized prostate cancer [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 1316.

Abstract NG06: CHD1-loss confers AR targeted therapy resistance via promoting cancer heterogeneity and lineage plasticity

Abstract NG06: CHD1-loss confers AR targeted therapy resistance via promoting cancer heterogeneity and lineage plasticity

Clinical Applications of Molecular Biomarkers in Prostate Cancer.

There is clinically relevant molecular heterogeneity in prostate cancer (PCa), but this biological diversity has had only a minimal impact on clinical practice. Treatment outcomes in patients with localised PCa are often highly variable, even among patients stratified to the same risk group or disease state based on standard clinical and pathological parameters. In recent years, the development of gene panels has provided valuable data on the differential expression of genes in patients with PCa. Nevertheless, there is an urgent need to identify and validate prognostic and predictive biomarkers that can be applied across clinical scenarios, ranging from localised disease to metastatic castration-resistant PCa. The availability of such tools would allow for precision medicine to finally reach PCa patients. In this review, we evaluate current data on molecular biomarkers for PCa, with an emphasis on the biomarkers and gene panels with the most robust evidence to support their application in routine clinical practice.

Dissection of primary prostate cancer to determine the clonal origin of synchronous lymph node metastasis.

e17614 Background: Primary prostate cancer often consists of multiple, genomically-distinct clones. The clonal source of lymph node metastasis in multifocal disease is unknown. We sought to analyze and determine the histopathologic and molecular characteristics of the tumor sub-clones capable of metastasis in primary prostate cancers with synchronous lymph node metastasis. Methods: We identified patients with primary prostate cancer found to have lymph node (LN) metastasis at the time of radical prostatectomy, including those with multifocal disease. Punch biopsies were obtained from multiple regions of primary tumors and LN metastases. Targeted next generation sequencing to assess somatic DNA mutations, copy number alterations (CNA), and TMPRSS2:ERG fusion status. Bioinformatic analyses were performed using in-house developed pipelines. Phylogenetic evolutionary analyses were performed to delineate the primary cancer clone responsible for LN metastasis. Results: We identified 2 patients with LN cancer regions. In one patient, while all four Grade Group (GG) 5 primary tumor (PT) regions showed concordant TP53 and TPR non-synonymous mutations and broad copy number alterations (CNAs) with two LN foci, only two regions shared high level CNAs with both lymph node foci. In this case, a GG1 tumor focus showed no TP53 somatic mutation or CNA overlap with the high-grade tumor or lymph node samples. Critically, phylogenetic analysis revealed that the GG5 PT with extra-prostatic extension (EPE) showed higher concordance with the LN metastases than regions confined to the prostate. In another patient with four PT, phylogenetic analysis revealed that the PT with EPE closely resembled the LN metastasis; both were TMPRSS2:ERG fusion positive share PTEN copy number loss. Two PT (GG1 and 2) appeared to be independent clones and were TMPRSS2:ERG fusion negative. One of the six circulating tumor cells (isolated pre-prostatectomy) from this patient demonstrated a significant PTEN copy loss consistent with the findings in the region of EPE and the LN metastasis. Conclusions: Our findings confirm molecular heterogeneity of primary prostate cancers and homogeneity of LN metastases supporting the use of shared molecular alterations to infer clonal lineage. Our results highlight the critical role of adverse pathologic features, such as grade and EPE, in prostate cancer with synchronous lymph node metastasis.

Wnt/β-catenin signaling contributes to prostate cancer heterogeneity through reciprocal suppression of H3K27 trimethylation

Intratumoral heterogeneity remains as a major challenge in the treatment resistance of prostate cancer. Understanding the mechanism of prostate cancer heterogeneity is essential for developing effective therapies. In this study, we reported the heterogeneous activation of Wnt/β-catenin signaling in prostate cancer. We developed a Wnt/β-catenin signaling reporting system to directly characterize the differences between Wnt/β-catenin signaling active (GFP+) and inactive (GFP−) cells. Compared to GFP− cells, GFP+ cells demonstrated cancer stem cell properties with higher colony formation efficiency, slower cell cycle, higher resistance to docetaxel and higher expression of cancer stem cell markers. In addition, we found that Wnt/β-catenin signaling is negatively correlated with H3K27me3 levels. Further studies demonstrated that Wnt/β-catenin signaling affected H3K27me3 levels by regulating the expression of KDM6A, one of the H3K27me3 demethylases. H3K27me3 suppressed Wnt/β-catenin signaling by directly silencing LEF1 promoter. Together, our studies suggest that Wnt/β-catenin signaling makes a major contribution to prostate cancer heterogeneity and targeting both Wnt/β-catenin signaling active and inactive populations is essential for developing more effective therapies.

Intratumoral heterogeneity and genetic characteristics of prostate cancer.

Prostate cancer is a heterogeneous disease and optimum gene targeting treatment is often impermissible. We aim to determine the intratumoral genomic heterogeneity of prostate cancer and explore candidate genes for targeted therapy. Exome sequencing was performed on 37 samples from 16 patients with prostate cancer. Somatic variant analysis, copy number variant (CNV) analysis, clonal evolution analysis and variant spectrum analysis were used to study the intratumoral genomic heterogeneity and genetic characteristics of metastatic prostate cancer. Our study confirmed the high intratumoral genetic heterogeneity of prostate cancer in many aspects, including number of shared variants, tumor mutation burden (TMB), variant genes, CNV burden, weighted genome instability index (wGII), CNV profiles, clonal evolutionary process, variant spectrum and mutational signatures. Moreover, we identified several common genetic characteristics of prostate cancer. Alterations of DNA damage repair genes, RTK/RAS pathway associated gene RASGRF1 and autophagy gene EPG5 may be involved in tumorigenesis in prostate cancer. CNV burden and DNA damage repair (DDR) genes may be associated with metastasis of prostate cancer.

Biomarker analysis of the phase III IPATential150 trial of first-line ipatasertib (Ipat) plus abiraterone (Abi) in metastatic castration-resistant prostate cancer (mCRPC).

182 Background: IPATential150 is a randomized trial comparing Ipat + Abi vs placebo + Abi in patients (pts) with 1L mCRPC (NCT03072238). We evaluated the potential associations between PTEN loss, genomic alterations, and country of enrollment (East Asian [EAS] vs non-EAS). Methods: Before randomization, tumor samples (archival > 90%) were centrally tested for PTEN loss by VENTANA PTEN (SP218) immunohistochemistry (IHC) assay (N = 1101). Tumor genetic alterations were profiled by Foundation Medicine FoundationOne CDx (F1CDx) NGS assay (n = 735). Results: Of 1101 pts enrolled, 521 (47%) had PTEN loss by IHC. An overall 76% agreement was observed between PTEN IHC and F1CDx. TMPRSS2 fusion, alterations in TP53 and PTEN were most frequent (28%-32%). Alterations in PIK3CA, SPOP, APC, MYC, RAD21, and genes involved in DNA damage repair, including BRCA2, CDK12, ATM, had a 5%-8% prevalence. PTEN loss (IHC) tended to co-occur with genetic alterations in TP53 and TMPRSS2. The prevalence of PTEN loss in EAS vs non-EAS pts was 35% vs 50% by IHC and 15% vs 31% by F1CDx. Alterations in CDK12, BRCA2, SPOP, and MYC were more prevalent in EAS pts, whereas alterations in TMPRSS2, PTEN, and TP53 were more prevalent in non-EAS pts. Conclusions: This analysis reveals molecular heterogeneity in prostate cancer and association between potentially actionable targets. It also suggests that EAS pts with mCRPC have a genetic profile that may be at least quantitatively different from non-EAS pts. Clinical trial information: NCT03072238. [Table: see text]

Multiparametric magnetic resonance imaging of multifocal prostate cancer to reveal intra-prostatic genomic heterogeneity and novel radio-genomic correlates: Results of the Smarter Prostate Interventions and Therapeutics (SPIRIT) study.

20 Background: Multi-focality and heterogeneity in prostate cancer can confound the selection of appropriate clinical management. Our study aimed to explore radio-genomic correlations using multiparametric magnetic resonance imaging (mpMRI) against a histopathologic reference standard. Methods: Eight men with prostate cancer who underwent mpMRI followed by prostatectomy were selected for this pilot. Whole-mount histopathology was digitized and co-registered to corresponding MRI slices using a validated high-fidelity methodology.(1) Foci, including central/transitional and peripheral zone lesions were identified by a pathologist, and contoured on digitized histopathology specimens and these digitized maps were used to guide macrodissection of the individual foci for genomic copy-number aberration (CNA) analysis. Correlation of radiomics signatures with the histologic findings and genomic analysis was performed. Results: We found a broad range of CNAs revealing inter-patient and intra-prostatic heterogeneity. Recurrently-altered loci ( e.g., 8p21) containing genes of known significance ( e.g., NKX3-1) were observed. Only radiomic features derived from apparent diffusion coefficient (ADC) independently correlated with both Gleason grade (Rho=-0.62, p=0.003) and median CNA burden (Rho=-0.68, p<0.001). While greater CNA burden expectedly correlated with higher grade, intermediate-grade (Gleason score 3+4 or 4+3) lesions appeared more like either high-grade (Gleason scores ≥4+4) or low-grade (Gleason score 3+3) disease when clustered based on CNA and ADC metrics. Conclusions: These findings suggest ADC derived radiomic metrics may be a useful imaging biomarker across both central and peripheral zone lesion and could aid in further characterization of intra-prostatic biologic heterogeneity. These proof-of-principle data reveal novel radio-genomic correlations that could supplement histologic grading and conventional imaging, thus warranting expanded study and validation. 1) Int J Rad Oncol Biol Phys. 2016; 96(1):188-96.

Abstract P4-01-09: Phenotypic profiling of circulating tumor cells (CTCs) in patients with metastatic breast cancer reveals clinically-relevant heterogeneity in CTC morphology and marker expression

Abstract Background: The choice between hormonal therapies and chemotherapy is a frequent decision in the standard of care of metastatic breast cancer (mBCa) patients. We previously developed quantitative measures of phenotypic CTC heterogeneity in metastatic prostate cancer and found that higher heterogeneity was associated with better survival on chemotherapy vs. targeted hormonal therapies in a risk adjusted analysis (Scher et al. 2017 Cancer Research). Here we sought to test the feasibility of measuring CTC heterogeneity in mBCa patients. Methods: 295 blood samples from 165 pts (84 HR+, 19 Her2+, 8 HR+/Her2+, 54 TNBC) from mBCa patients were processed for CTC analysis utilizing the Epic Sciences Functional Cell Profiling platform. Following enumeration, multi-dimensional phenotypic characterization analysis was performed utilizing protein expression and digital pathology features. Features from each CTC (3994 CTCs from 165 pts, were compared by unsupervised clustering to assess intra-patient CTC heterogeneity among mBCa CTC phenotypes. Results: CTCs were detected in 76.9% (227/295) of mBCa patients (med=2.4 CTC/mL, Range 0 - 747). Phenotypic profiling identified distinct CTC subtypes characterized by morphological and protein expression features that correlated with mBCa subtypes. Prevalent CTC features that associated with mBCa were either high cytokeratin (CK) expression or lower nuclear to cytoplasmic (N/C) ratio with lower CK expression. Analysis of mBCa subtypes showed that TNBC pts were characterized by CTCs with a large nuclear area and high CK expression. We observed marked differences in CTC heterogeneity across patients, with some patients having more uniform CTC profiles, and others having higher phenotypic diversity. mBCa subtypes had similar intra-patient heterogeneity level. Conclusions: Distinct CTC phenotypes can be visualized and quantified across patients and associated with specific mBCa subtypes. Our analysis revealed significant heterogeneity between individual CTCs both between and within patients. Identification of patients with high heterogeneity may help to identify patients unlikely to respond to targeted therapies. Studies to link heterogeneity to efficacy of specific therapies and patient outcome are ongoing. Citation Format: Tiziano Pramparo, Adam Jendrisak, Priscilla Ontiveros, Megan Kearney, Lincy Chu, Nadia Ebrahim, Joseph Schonhoft, Rick Wenstrup, Yipeng Wang. Phenotypic profiling of circulating tumor cells (CTCs) in patients with metastatic breast cancer reveals clinically-relevant heterogeneity in CTC morphology and marker expression [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-01-09.

Re: Prostate-specific Membrane Antigen Heterogeneity and DNA Repair Defects in Prostate Cancer.

Re: Prostate-specific Membrane Antigen Heterogeneity and DNA Repair Defects in Prostate Cancer.

Multiparametric MRI as a Biomarker of Response to Neoadjuvant Therapy for Localized Prostate Cancer–A Pilot Study

To explore a role for multiparametric MRI (mpMRI) as a biomarker of response to neoadjuvant androgen deprivation therapy (ADT) for prostate cancer (PCa). This prospective study was approved by the institutional review board and was HIPAA compliant. Eight patients with localized PCa had a baseline mpMRI, repeated after 6-months of ADT, followed by prostatectomy. mpMRI indices were extracted from tumor and normal regions of interest (TROI/NROI). Residual cancer burden (RCB) was measured on mpMRI and on the prostatectomy specimen. Paired t-tests compared TROI/NROI mpMRI indices and pre/post-treatment TROI mpMRI indices. Spearman's rank tested for correlations between MRI/pathology-based RCB, and between pathological RCB and mpMRI indices. At baseline, TROI apparent diffusion coefficient (ADC) was lower and dynamic contrast enhanced (DCE) metrics were higher, compared to NROI (ADC: 806 ± 137 × 10-6 vs. 1277 ± 213 × 10-6 mm2/sec, p = 0.0005; Ktrans: 0.346 ± 0.16 vs. 0.144 ± 0.06 min-1, p = 0.002; AUC90: 0.213 ± 0.08 vs. 0.11 ± 0.03, p = 0.002). Post-treatment, there was no change in TROI ADC, but a decrease in TROI Ktrans (0.346 ± 0.16 to 0.188 ± 0.08 min-1; p = 0.02) and AUC90 (0.213 ± 0.08 to 0.13 ± 0.06; p = 0.02). Tumor volume decreased with ADT. There was no difference between mpMRI-based and pathology-based RCB, which positively correlated (⍴ = 0.74-0.81, p < 0.05). Pathology-based RCB positively correlated with post-treatment DCE metrics (⍴ = 0.76-0.70, p < 0.05) and negatively with ADC (⍴ = -0.79, p = 0.03). Given the heterogeneity of PCa, an individualized approach to ADT may maximize potential benefit. This pilot study suggests that mpMRI may serve as a biomarker of ADT response and as a surrogate for RCB at prostatectomy.

Comprehensive Analysis of AR Alterations in Circulating Tumor DNA from Patients with Advanced Prostate Cancer.

Somatic alterations in circulating tumor DNA (ctDNA) may be associated with treatment response or prognosis in prostate cancer (PCa). The goal was to characterize androgen receptor gene (AR) amplifications and mutations detected in ctDNA from patients with PCa and to further understand the somatic genetic heterogeneity of advanced prostate cancer. This study included a heterogeneous group of 892 patients with advanced PCa (predominantly castrate-resistant prostate cancer) with AR alterations detected in ctDNA that underwent next-generation sequencing of 54 to 73 genes via Guardant360 testing (Guardant Health, Inc., Redwood City, CA). Distribution and summary of AR alterations detected, the association of AR alterations with other genes, and a pathway analysis are reported. The median absolute plasma copy number of AR amplifications was 3.3 (range, 1.2-165.2). Many patients had multiple AR mutations; a total of 112 unique mutations were identified in AR, including L702H (25%), T878A (14%), H875Y (11%), W742C (8%), W742L (4%), F877L (2%), and T878S (2%). Other ctDNA gene alterations in the Guardant assays included TP53 (50%), MYC (34%), BRAF (32%), PIK3CA (29%), MET (25%), CDK6 (26%), EGFR (24%), FGFR1 (21%), and APC (12%). Many of these non-AR alterations are not tissue verified in other studies. AR amplification cosegregated with alterations in MYC (p < .001), BRAF (p < .001), PIK3CA (p < .001), MET (p < .001), CDK6 (p < .001), EGFR (p < .001), FGFR1 (p = .391), and more. Alterations in APC were significantly associated with mutations in AR (p < .001). Several AR alterations and concomitant non-AR alterations that associate with drug resistance were detected. These findings provide additional insights into the heterogeneity of advanced prostate cancer. The goal was to characterize androgen receptor gene (AR) amplifications and mutations detected in circulating tumor DNA (ctDNA) from patients with prostate cancer in relation to non-AR gene alterations detected in the ctDNA landscape. The study included 892 patients with prostate cancer with AR alterations in ctDNA. AR alterations were significantly associated with other gene alterations detected in ctDNA. The common AR mutations found are linked to resistance to abiraterone, enzalutamide, or bicalutamide. Characterization of the circulating AR landscape and gene alterations provides potential additional insight into the somatic genetic heterogeneity of advanced prostate cancer.

Transcriptome Network Analysis Identifies CXCL13-CXCR5 Signaling Modules in the Prostate Tumor Immune Microenvironment

The tumor immune microenvironment (TIME) consists of multiple cell types that contribute to the heterogeneity and complexity of prostate cancer (PCa). In this study, we sought to understand the gene-expression signature of patients with primary prostate tumors by investigating the co-expression profiles of patient samples and their corresponding clinical outcomes, in particular “disease-free months” and “disease reoccurrence”. We tested the hypothesis that the CXCL13-CXCR5 axis is co-expressed with factors supporting TIME and PCa progression. Gene expression counts, with clinical attributes from PCa patients, were acquired from TCGA. Profiles of PCa patients were used to identify key drivers that influence or regulate CXCL13-CXCR5 signaling. Weighted gene co-expression network analysis (WGCNA) was applied to identify co-expression patterns among CXCL13-CXCR5, associated genes, and key genetic drivers within the CXCL13-CXCR5 signaling pathway. The processing of downloaded data files began with quality checks using NOISeq, followed by WGCNA. Our results confirmed the quality of the TCGA transcriptome data, identified 12 co-expression networks, and demonstrated that CXCL13, CXCR5 and associated genes are members of signaling networks (modules) associated with G protein coupled receptor (GPCR) responsiveness, invasion/migration, immune checkpoint, and innate immunity. We also identified top canonical pathways and upstream regulators associated with CXCL13-CXCR5 expression and function.

Prostate-specific Membrane Antigen Heterogeneity and DNA Repair Defects in Prostate Cancer

BackgroundProstate-specific membrane antigen (PSMA; folate hydrolase) prostate cancer (PC) expression has theranostic utility. ObjectiveTo elucidate PC PSMA expression and associate this with defective DNA damage repair (DDR). Design, setting, and participantsMembranous 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 analysisExpression 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 limitationsExpression 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. ConclusionsMembranous 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 summaryThrough 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.

Abstract 4693: Evaluation of prostate tumor molecular heterogeneity using whole mount radical prostatectomy by dual immunohistochemistry and dual RNA in situ hybridization

Abstract Prostate cancer (PCa) remains the second most common cancer among American men. Morphological heterogeneity in prostate cancer is well recognized, however, recent investigations revealed molecular heterogeneity with the existence of unique molecular aberrations among patient sub groups. Molecular heterogeneity may be associated with distinct routes of disease progression, thereby, enabling the use of molecular profiling to facilitate targeted therapy. Importantly, African Americans (AA) are known to develop more aggressive forms of PCa compared to Caucasian Americans (CA). Therefore, the identification of distinct molecular profiles between the two groups may lead to more precise treatment options for PCa patients. Given that a comprehensive molecular mapping, encompassing both AA and CA patients is lacking, we carried out an extensive profiling of multiple molecular markers in a large cohort of AA and CA PCa patients. Whole-mounted post-prostatectomy tissues were obtained from 1117 patients who underwent radical prostatectomy surgery at our institute. The selected cases included 575 (52%) CA and 453 (41%) AA patients. The presence of ERG, SPINK1, ETV1, ETV4 and ETV5 was evaluated using dual IHC and dual RNA ISH. The racial disparity in the molecular marker incidence was analyzed. The incidence of ERG was observed in 52.0% (436/839) of cases while SPINK1 incidence occurred in 45.1% (378/838) cases. The incidence of other ERG family rearrangements, ETV1, ETV4 and ETV5 was low with 9.9% (78/791), 3.8 % (28/733) and 0.6% (2/350) cases respectively. A total of 260 cases showed the incidence of multiple markers on a single prostate. Of these, ERG+/SPINK1+ was prominent with an incidence of 18% (151/838), followed by ERG+/ETV1+ which occurred in 5.2% cases (41/790). In most cases, multiple marker incidence was detected in separate foci, supporting the independent clonal origin of tumor foci in patients with multi focal disease. In a subset of cases, the co-occurrence of ERG and SPINK1 in the same foci was observed, suggesting intra tumor heterogeneity, however, in majority of the cases mutually exclusive pattern of expression was observed, indicating the presence of unique driver molecular aberrations in each tumor foci.. Statistical analysis revealed significant incidence of ERG+ in CA (P=0.00) and SPINK1 in AA patients (P=0.00). Additionally, the incidence of ERG/SPINK1 and SPINK1/ETV1 were more frequent among AA patients compared to CA patients (P=0.0124 and P=0.0417). In conclusion, our study highlights the existence of significant molecular heterogeneity among PCa patients in a racially disparate perspective. Consequently, a thorough understanding of the clinical association between distinct molecular sub groups and disease progression in each racial group will significantly aid the treatment efforts in combatting PCa disease. Citation Format: Pavithra D. Arachchige, Shannon Carskadon, Gaury Dhamdhere, Mireya Diaz-Insua, Hans Stricker, Craig Rogers, James Peabody, Mani Menon, Sean Williamson, Nilesh Gupta, Nallasivam Palanisamy. Evaluation of prostate tumor molecular heterogeneity using whole mount radical prostatectomy by dual immunohistochemistry and dual RNA in situ hybridization [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4693.

PSMA heterogeneity and DNA repair defects in prostate cancer.

5002 Background: Prostate-specific membrane antigen (PSMA) is a promising target for theranostics in metastatic castration resistant prostate cancer (mCRPC). Methods: Membranous PSMA (mPSMA) expression was immunohistochemically evaluated in castration sensitive (CSPC) (n = 38) and mCRPC (n = 60) tissue biopsies, and associations with molecular aberrations (next-generation sequencing; NGS) and clinical outcome were determined. Results: mPSMA expression was significantly higher (p = 0.005) in mCRPC biopsies (median H-score [interquartile range]; 55.0 [2.8-117.5]) compared to CSPC biopsies (17.5 [0.0-60.0]). Furthermore, patients with higher mPSMA expression ( &gt; median H-score) at diagnosis had higher Gleason Grade (p = 0.04) and shorter OS (p = 0.006). Critically, 42% (16/38) of CSPC biopsies and 27% (16/60) of mCRPC biopsies were completely negative for mPSMA expression. In addition, CSPC and mCRPC biopsies expressing mPSMA demonstrated marked intra-tumor heterogeneity in expression levels, commonly exhibiting areas without detectable PSMA (CSPC – 100%; mCRPC – 84%), while heterogeneous mPSMA expression between metastases from the same patient was also observed. Subsequent genomic analysis showed that mCRPC patients with deleterious DNA damage repair (DDR) aberrations have higher (p = 0.016) mPSMA expression (87.5 [25.0-247.5]) than those without these (20 [0.3-98.8]). Furthermore, 9 of the 11 patients (82%) responding to PARP inhibition had a mPSMA H-Score above the median. The association between mPSMA expression and DDR aberrations was validated in an independent cohort with known DDR aberrations. Tumors with DDR aberrations had significantly higher mPSMA (ATM 212.5 [136.3-300] p = 0.005; BRCA2 300 [165-300] p = &lt; 0.001) than unselected mCRPC biopsies (55.0 [2.75-117.5]). Finally, analyses of 122 mCRPC biopsy transcriptomes confirmed a negative correlation between PSMA and BRCA2 mRNA expression (p = 1.5x10-5). Conclusions: mPSMA expression in CSPC and mCRPC exhibits marked intra- and inter-patient heterogeneity, limiting the clinical utility of PSMA-targeted theranostics. We show for the first time that DDR gene aberrations associate with high mPSMA expression and may serve as predictive biomarkers for PSMA-targeted therapies.

Establishment and characterization of a prostate cancer cell line from a prostatectomy specimen for the study of cellular interaction.

Though human prostate cancer (PCa) heterogeneity can best be studied using multiple cell types isolated from clinical specimens, the difficulty of establishing cell lines from clinical tumors has hampered this approach. In this proof-of-concept study, we established a human PCa cell line from a prostatectomy surgical specimen without the need for retroviral transduction. In a previous report, we characterized the stromal cells derived from PCa specimens. Here, we characterized the epithelial cells isolated from the same tumors. Compared to the ease of establishing prostate stromal cell lines, prostatic epithelial cell lines are challenging. From three matched pairs of normal and tumor tissues, we established one new PCa cell line, HPE-15. We confirmed the origin of HPE-15 cells by short tandem repeat microsatellite polymorphism analysis. HPE-15 cells are androgen-insensitive and express marginal androgen receptor, prostate-specific antigen and prostate-specific membrane antigen proteins. HPE-15 expresses luminal epithelial markers of E-cadherin and cytokeratin 18, basal cell markers of cytokeratin 5 and p63 and neuroendocrine marker of chromogranin A. Interestingly, HPE-15 Cells exhibited no tumorigenicity in different strains of immune-deficient mice but can become tumorigenic through interaction with aggressive cancer cell types. HPE-15 cells can thus serve as an experimental model for the study of PCa progression, metastasis and tumor cell dormancy.

A TMEFF2-regulated cell cycle derived gene signature is prognostic of recurrence risk in prostate cancer

BackgroundThe clinical behavior of prostate cancer (PCa) is variable, and while the majority of cases remain indolent, 10% of patients progress to deadly forms of the disease. Current clinical predictors used at the time of diagnosis have limitations to accurately establish progression risk. Here we describe the development of a tumor suppressor regulated, cell-cycle gene expression based prognostic signature for PCa, and validate its independent contribution to risk stratification in several radical prostatectomy (RP) patient cohorts.MethodsWe used RNA interference experiments in PCa cell lines to identify a gene expression based gene signature associated with Tmeff2, an androgen regulated, tumor suppressor gene whose expression shows remarkable heterogeneity in PCa. Gene expression was confirmed by qRT-PCR. Correlation of the signature with disease outcome (time to recurrence) was retrospectively evaluated in four geographically different cohorts of patients that underwent RP (834 samples), using multivariate logistical regression analysis. Multivariate analyses were adjusted for standard clinicopathological variables. Performance of the signature was compared to previously described gene expression based signatures using the SigCheck software.ResultsLow levels of TMEFF2 mRNA significantly (p < 0.0001) correlated with reduced disease-free survival (DFS) in patients from the Memorial Sloan Kettering Cancer Center (MSKCC) dataset. We identified a panel of 11 TMEFF2 regulated cell cycle related genes (TMCC11), with strong prognostic value. TMCC11 expression was significantly associated with time to recurrence after prostatectomy in four geographically different patient cohorts (2.9 ≤ HR ≥ 4.1; p ≤ 0.002), served as an independent indicator of poor prognosis in the four RP cohorts (1.96 ≤ HR ≥ 4.28; p ≤ 0.032) and improved the prognostic value of standard clinicopathological markers. The prognostic ability of TMCC11 panel exceeded previously published oncogenic gene signatures (p = 0.00017).ConclusionsThis study provides evidence that the TMCC11 gene signature is a robust independent prognostic marker for PCa, reveals the value of using highly heterogeneously expressed genes, like Tmeff2, as guides to discover prognostic indicators, and suggests the possibility that low Tmeff2 expression marks a distinct subclass of PCa.

Merging new-age biomarkers and nanodiagnostics for precision prostate cancer management.

The accurate identification and stratified treatment of clinically significant early-stage prostate cancer have been ongoing concerns since the outcomes of large international prostate cancer screening trials were reported. The controversy surrounding clinical and cost benefits of prostate cancer screening has highlighted the lack of strategies for discriminating high-risk disease (that requires early treatment) from low-risk disease (that could be managed using watchful waiting or active surveillance). Advances in molecular subtyping and multiomics nanotechnology-based prostate cancer risk delineation can enable refinement of prostate cancer molecular taxonomy into clinically meaningful and treatable subtypes. Furthermore, the presence of intertumoural and intratumoural heterogeneity in prostate cancer warrants the development of novel nanodiagnostic technologies to identify clinically significant prostate cancer in a rapid, cost-effective and accurate manner. Circulating and urinary next-generation prostate cancer biomarkers for disease molecular subtyping and the newest complementary nanodiagnostic platforms for enhanced biomarker detection are promising tools for precision prostate cancer management. However, challenges in merging both aspects and clinical translation still need to be overcome.