Prostate Cancer Biology Research Articles

High stroma-derived WNT5A is an indicator for low-risk prostate cancer.

Prostate cancer (PCa) is a major cause of cancer‐related death in men. Tumor‐derived protein derived from Wnt5A gene (WNT5A) plays an important role in primary and metastatic PCa. Surrounding stroma cells also produce WNT5A, which may modulate the biology of PCa. Here, we assessed the role of stroma‐derived WNT5A (stWNT5A) in primary PCa. A tissue microarray of samples obtained from 400 patients who underwent radical prostatectomy and control samples from 41 patients with benign prostate hyperplasia (BPH) was immunohistochemically assessed for expression of stWNT5A. The cores were scored for staining intensity: 0 (no staining), 1 (weak), 2 (moderate), or 3 (strong) and the stained stromal surface area: 0 (0%), 1 (1–25%), 2 (26–50%), 3 (51–75%), or 4 (76–100%). Gleason Score (GS) and TNM‐stage were assessed by stratifying the cohort into high‐risk (≥ pT3, pN1, GS ≥ 8) and non‐high‐risk patients. Ki67 and TUNEL assays were performed to assess proliferation and apoptosis. Expression of stWNT5A in BPH and tumor‐free control samples was 1.2‐fold higher compared to tumor samples (P < 0.001). Non‐high‐risk patients had a higher stWNT5A score than high‐risk patients (P < 0.05). stWNT5A expression was not correlated with overall and cancer‐specific survival. Proliferation (r 2 = 0.038, P < 0.001) and apoptosis (r 2 = 0.277, P < 0.001) negatively correlated with stWNT5A expression. In summary, we show that expression of stWNT5A is higher in benign tissue and non‐high‐risk PCa. Stroma‐derived Wnt signaling and tumor‐derived Wnt may differentially impact on tumor behavior. Future studies are warranted to dissect the Wnt profile in tumor vs. surrounding stroma tissues.

Gut microbiota-associated compounds increase lethal prostate cancer risk.

147 Background: Gut-microbiota-mediated metabolism of trimethylamine-associated nutrients and amino acids has been linked to altered cholesterol metabolism and endothelial inflammation. However, the association between these compounds and lethal prostate cancer (PCa) remains unknown. Methods: A nested case-control study was performed using samples from the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial to evaluate the association between baseline serum levels of target metabolites (choline, carnitine, betaine, γ-butyrobetaine, crotonobetaine, trimethylamine N-oxide, phenylacetylglutamine, hippuric acid, and p-cresol sulfate) and lethal PCa risk. Lethal cases were randomly matched to controls at a 1:3 ratio on the basis of age, race, and enrollment date. Multivariable logistic regression, conditioned on case status and adjusted for PSA and BMI, was performed to assess the association between analyte quartile (Q) with lethal PCa. Trend of increasing odd ratios (OR) was evaluated using the Cochran-Armitage test. Results: 173 lethal PCa cases and 519 controls were analyzed. Relative to those in Q1, cases with baseline levels of choline and betaine above the median exhibited increased odds of developing lethal PCa after adjusting for BMI and PSA (Table). Lethal PCa risk increased across quartiles of choline in a dose-dependent fashion ( P-trend: 0.005), but not for betaine (P-trend: 0.08). Higher serum levels of other trimethylamine-associated compounds including γ-butyrobetaine, crotonobetaine, trimethylamine N-oxide were not consistently associated with PCa mortality. Baseline serum levels of phenylacetylglutamine, a gut-microbiota metabolite of phenylalanine, were associated with incident lethal PCa, with risk increasing across quantiles (P-trend: 0.003). Elevations in hippuric acid and p-cresol sulfate levels were not consistently associated with greater lethal PCa risk. Conclusions: Serum levels choline, betaine, and phenylacetylglutamine are associated with PCa mortality, underscoring the potential role of gut-microbiota-mediated metabolism in the biology of lethal PCa. Clinical trial information: NCT00002540. [Table: see text]

Understanding the tumor-immune microenvironment in prostate cancer.

This review aims to highlight recent advances in prostate cancer tumor-immune microenvironment research and summarize the state-of-the-art knowledge of immune checkpoint inhibitors in prostate cancer. Immune checkpoint inhibitors are the cornerstone of modern immunotherapy which have shown encouraging results across a spectrum of cancers. However, only limited survival benefit has been seen in patients with prostate cancer. Prostate cancer progression and its response to immunotherapies are strongly influenced by the tumor-immune microenvironment, whose feature can be summarized as low amounts of tumor-specific antigens, low frequency of tumor-infiltrating lymphocytes and high frequency of tumor-associated macrophages. To improve the therapeutic effect of immunotherapies, in recent years, many strategies have been applied, of which the most promising ones include the combination of multiple immunotherapeutic agents, the combination of an immunotherapeutic agent with other modalities in parallel or in sequential, and the development of biomarkers to find a subgroup of patients who may benefit the most from immunotherapeutic agents. The impact of immune content and specific immune cell types on prostate cancer biology is highly complex. Recent clinical trials have shed light on the optimal use of immunotherapies for prostate cancer.

Tumor biology of metastatic prostate cancer: clinical implications

Tumor biology of metastatic prostate cancer: clinical implications

Prostate cancer genetics and biology:&#x0D; literature review

Prostate cancer genetics and biology:&#x0D; literature review

Prostate cancer genetics&#x0D; and biology

Relevance: Despite a high survival with localized&#x0D; prostate cancer, metastatic prostate cancer remains&#x0D; virtually incurable even after intensive multimodal therapy. Death in advanced stages of the disease is caused&#x0D; by the lack of therapeutic regimens able to produce a&#x0D; long-term tumor reaction due to its extreme genetic and&#x0D; cellular heterogeneity. According to epidemiological&#x0D; studies, a family history of prostate cancer significantly&#x0D; increases the risk. Clinical diagnosis is often based on a&#x0D; single biopsy made to determine the molecular status of&#x0D; a particular cancer case. Pathological and genomic heterogeneity can lead to bias in diagnosis. Therefore, the&#x0D; use of genetic research technologies is highly relevant.&#x0D; The purpose wasto justify the use of genetic profiling technologies for patients with prostate cancer.&#x0D; Results: Many cases lack an understanding of the&#x0D; multifactorial impact of current treatment methods&#x0D; on the patient’s immune system. Combination therapy efficacy and tolerability depend on the choice of an&#x0D; optimal treatment regimen. Approaches to prioritizing&#x0D; the types of combination therapy should be developed.&#x0D; Cancer genome affects the disease course and progression. Simulation of these interactions in a genetic model&#x0D; allows predicting the treatment outcome and effectiveness.&#x0D; Conclusions: The conducted systematic review&#x0D; shows that a deep understanding of prostate cancer biology and genetics and genetic profiling can save and&#x0D; improve the lives of many patients with serious diseases.

Abstract PO-094: Mass spectrometry imaging of N-glycans identifies racial discrepancies in human prostate tumors

Abstract Prostate cancer is the most commonly diagnosed cancer in men worldwide. A critical knowledge gap in prostate cancer biology is the molecular events underlining higher incidence and mortality rate in Black men. Identifying molecular features that separate racial disparities is a critical step in prostate cancer research that could lead to predictive biomarkers and personalized therapy. N-linked glycosylation is a required co-translational event during protein folding that modulates many biological processes, such as cell adhesion, immune modulation, cell-matrix interactions, and cell proliferation. Recently, aberrant N-linked glycosylation has been reported in prostate cancers. However, the full clinical implications of dysregulated glycosylation in prostate cancer has yet to be explored. Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) is a new and innovative technique that combines mass spectrometry with imaging, enabling the detection of glycans with spatial distribution. Herein, we performed MALDI-MSI analysis to characterize the N-glycan profile from tissue microarrays of over 100 patient tumors banked at the University of Kentucky with over 10 years of follow-up data. Additionally, we performed MALDI-MSI analysis on large sections of prostate cancer to define the regional distribution of N-glycans within the tumor microenvironment. We successfully identified 46 unique glycans from readily available formalin-fixed paraffin-embedded prostate tissue, and found significant N- glycan dysregulation between benign and prostate tumor tissue across all patient groups. High mannose as well as tri- and tetra-antennary N-glycans were predominantly found in tumor tissue and correlate with increased tumor grade. Surprisingly, several species of N-glycans were profoundly different between early grade prostate tumors resected from White and Black patients. Further, these glycans predict opposing overall survival between White and Black patients with prostate cancer. These data suggest differential N-linked glycosylation underline the racial disparity of prostate cancer prognosis. Our study highlights the potential clinical applications of MALDI-MSI for digital pathology and biomarker applications, and reveals molecular features that contribute to the racial disparity in diagnosis and survival of prostate cancer patients. Citation Format: Lindsey R. Conroy, Lyndsay E.A. Young, Grant L. Austin, Alexanda E. Stanback, Derek B Allison, Matthew S. Gentry, Richard R. Drake, Ramon C. Sun. Mass spectrometry imaging of N-glycans identifies racial discrepancies in human prostate tumors [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-094.

Laboratory-wide association study of survival with prostate cancer.

Estimates of overall patient health are essential to inform treatment decisions for patients diagnosed with cancer. The authors applied XWAS methods, herein referred to as "laboratory-wide association study (LWAS)", to evaluate associations between routinely collected laboratory tests and survival in veterans with prostate cancer. The authors identified 133,878 patients who were diagnosed with prostate cancer between 2000 and 2013 in the Veterans Health Administration using any laboratory tests collected within 6 months of diagnosis (3,345,083 results). Using the LWAS framework, the false-discovery rate was used to test the association between multiple laboratory tests and survival, and these results were validated using training, testing, and validation cohorts. A total of 31 laboratory tests associated with survival met stringent LWAS criteria. LWAS confirmed markers of prostate cancer biology (prostate-specific antigen: hazard ratio [HR], 1.07 [95% confidence interval (95% CI), 1.06-1.08]; and alkaline phosphatase: HR, 1.22 [95% CI, 1.20-1.24]) as well laboratory tests of general health (eg, serum albumin: HR, 0.78 [95% CI, 0.76-0.80]; and creatinine: HR, 1.05 [95% CI, 1.03-1.07]) and inflammation (leukocyte count: HR, 1.23 [95% CI, 1.98-1.26]; and erythrocyte sedimentation rate: HR, 1.33 [95% CI, 1.09-1.61]). In addition, the authors derived and validated separate models for patients with localized and advanced disease, identifying 28 laboratory markers and 15 laboratory markers, respectively, in each cohort. The authors identified routinely collected laboratory data associated with survival for patients with prostate cancer using LWAS methodologies, including markers of prostate cancer biology, overall health, and inflammation. Broadening consideration of determinants of survival beyond those related to cancer itself could help to inform the design of clinical trials and aid in shared decision making. This article examined routine laboratory tests associated with survival among veterans with prostate cancer. Using laboratory-wide association studies, the authors identified 31 laboratory tests associated with survival that can be used to inform the design of clinical trials and aid patients in shared decision making.

Abstract PO-085: Mass spectrometry imaging of N-glycans identifies racial discrepancies in human prostate tumors

Abstract Prostate cancer is the most commonly diagnosed cancer in men worldwide. A critical knowledge gap in prostate cancer biology is the molecular events underlining higher incidence and mortality rate in Black men. Identifying molecular features that separate racial disparities is a critical step in prostate cancer research that could lead to predictive biomarkers and personalized therapy. N-linked glycosylation is a required co-translational event during protein folding that modulates many biological processes, such as cell adhesion, immune modulation, cell-matrix interactions, and cell proliferation. Recently, aberrant N-linked glycosylation has been reported in prostate cancers. However, the full clinical implications of dysregulated glycosylation in prostate cancer has yet to be explored. Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) is a new and innovative technique that combines mass spectrometry with imaging, enabling the detection of glycans with spatial distribution. Herein, we performed MALDI-MSI analysis to characterize the N-glycan profile from tissue microarrays of over 100 patient tumors banked at the University of Kentucky with over 10 years of follow-up data. Additionally, we performed MALDI-MSI analysis on large sections of prostate cancer to define the regional distribution of N-glycans within the tumor microenvironment. We successfully identified 46 unique glycans from readily available formalin-fixed paraffin-embedded prostate tissue, and found significant N-glycan dysregulation between benign and prostate tumor tissue across all patient groups. High mannose as well as tri- and tetra-antennary N-glycans were predominantly found in tumor tissue and correlate with increased tumor grade. Surprisingly, several species of N-glycans were profoundly different between early grade prostate tumors resected from White and Black patients. Further, these glycans predict opposing overall survival between White and Black patients with prostate cancer. These data suggest differential N-linked glycosylation underline the racial disparity of prostate cancer prognosis. Our study highlights the potential clinical applications of MALDI-MSI for digital pathology and biomarker applications, and reveals molecular features that contribute to the racial disparity in diagnosis and survival of prostate cancer patients. Citation Format: Lindsey R. Conroy, Lyndsay E.A. Young, Grant L. Austin, Alexandra E. Stanback, Derek B. Allison, Matthew S. Gentry, Richard R. Drake, Ramon C. Sun. Mass spectrometry imaging of N-glycans identifies racial discrepancies in human prostate tumors [abstract]. In: Proceedings of the AACR Virtual Special Conference on Tumor Heterogeneity: From Single Cells to Clinical Impact; 2020 Sep 17-18. Philadelphia (PA): AACR; Cancer Res 2020;80(21 Suppl):Abstract nr PO-085.

YTHDF2 mediates the mRNA degradation of the tumor suppressors to induce AKT phosphorylation in N6-methyladenosine-dependent way in prostate cancer

BackgroundN6-methyladenosine (m6A) is the most abundant modification in mRNA of humans. Emerging evidence has supported the fact that m6A is comprehensively involved in various diseases especially cancers. As a crucial reader, YTHDF2 usually mediates the degradation of m6A-modified mRNAs in m6A-dependent way. However, the function and mechanisms of m6A especially YTHDF2 in prostate cancer (PCa) still remain elusive.MethodsTo investigate the functions and mechanisms of YTHDF2 in PCa, in vitro, in vivo biofunctional assays and epigenetics experiments were performed. Endogenous expression silencing of YTHDF2 and METTL3 was established with lentivirus-based shRNA technique. Colony formation, flow cytometry and trans-well assays were performed for cell function identifications. Subcutaneous xenografts and metastatic mice models were combined with in vivo imaging system to investigate the phenotypes when knocking down YTHDF2 and METTL3. m6A RNA immunoprecipitation (MeRIP) sequencing, mRNA sequencing, RIP-RT-qPCR and bioinformatics analysis were mainly used to screen and validate the direct common targets of YTHDF2 and METTL3. In addition, TCGA database was also used to analyze the expression pattern of YTHDF2, METTL3 and the common target LHPP in PCa, and their correlation with clinical prognosis.ResultsThe upregulated YTHDF2 and METTL3 in PCa predicted a worse overall survival rate. Knocking down YTHDF2 or METTL3 markedly inhibited the proliferation and migration of PCa in vivo and in vitro. LHPP and NKX3–1 were identified as the direct targets of both YTHDF2 and METTL3. YTHDF2 directly bound to the m6A modification sites of LHPP and NKX3–1 to mediate the mRNA degradation. Knock-down of YTHDF2 or METTL3 significantly induced the expression of LHPP and NKX3–1 at both mRNA and protein level with inhibited phosphorylated AKT. Overexpression of LHPP and NKX3–1 presented the consistent phenotypes and AKT phosphorylation inhibition with knock-down of YTHDF2 or METTL3. Phosphorylated AKT was consequently confirmed as the downstream of METTL3/YTHDF2/LHPP/NKX3–1 to induce tumor proliferation and migration.ConclusionWe propose a novel regulatory mechanism in which YTHDF2 mediates the mRNA degradation of the tumor suppressors LHPP and NKX3–1 in m6A-dependent way to regulate AKT phosphorylation-induced tumor progression in prostate cancer. We hope our findings may provide new concepts of PCa biology.

Association Between Black Race And Improved Survival Following Sipuleucel-T Immunotherapy In Metastatic Castrate-Resistant Prostate Cancer: Implications For Immune Biology And Integration Of Radiation Therapy With Immunotherapy

The biology of prostate cancer in black patients may differ from white patients. For example, recent data suggests that black patients may harbor tumors that are more sensitive to radiation or immune-directed therapy. Sipuleucel-T, a cell-based immunotherapy approved for use in men with metastatic castrate-resistant prostate cancer (mCRPC), is currently also being studied in early-stage non-metastatic prostate cancer. To explore possible immunologic differences and opportunities for synergy with radiation therapy, we examined the association between race and overall survival (OS) among patients receiving sipuleucel-T therapy for mCRPC using a novel real-world database. Using the CancerLinQ database, we identified 474 patients with mCRPC managed with sipuleucel-T. We used Cox modeling to examine the association between race (black vs white) and OS, with or without adjustment for other prognostic variables (age, prior systemic therapy, and prostate-specific antigen [PSA]), and performed subgroup analyses stratifying by the median PSA (16.6 ng/mL). In secondary analyses, we used Cox modeling to estimate treatment-free survival following sipuleucel-T and we used competing risks regression to model time to initiation of a subsequent systemic therapy. Median follow-up was 38.8 months. Black patients (n = 68) experienced significantly improved OS compared to white patients (n = 406) (median 43.1 months vs 30.2 months, hazard ratio [HR] = 0.638, 95% confidence interval [CI] 0.443-0.920, p = 0.016). These results persisted on multivariable analysis (adjusted HR 0.542, 95% CI 0.371-0.792, p = 0.002). Among patients with PSA > 16.6 ng/mL, median OS was 37.7 months vs 20.3 months (HR = 0.463, 95% CI 0.277-0.775, p = 0.003). For patients with PSA < = 16.6 ng/mL, there was no significant difference in median OS (43.1 months vs 40.6 months, HR = 0.842, 95% CI 0.487-1.456, p = 0.538). There were no significant differences in treatment-free survival (HR = 0.777, 95% CI 0.581-1.040, p = 0.090) or initiation of a subsequent systemic therapy (HR = 1.287, 95% CI 0.802-2.065, p = 0.295) by race. Black patients were more likely to receive subsequent cabazitaxel therapy compared to white patients (26.5% vs 15.0%, p = 0.019) but there were no significant differences in the receipt of other therapies (docetaxel, abiraterone, enzalutamide, radium-223). Among men with mCRPC who received sipuleucel-T, black patients had significantly longer OS compared to white patients but no difference in the time to subsequent systemic therapy, mirroring the results of prior immunotherapy studies. This finding may reflect differences in the underlying immune biology of prostate cancer in black versus white patients and may have implications for the integration of radiation therapy and immunotherapy in prostate cancer.

The 26th Annual Prostate Cancer Foundation Scientific Retreat Report.

The 26th Annual Prostate Cancer Foundation (PCF) Scientific Retreat was held from October 24-26, 2019 in Carlsbad, CA. The Annual PCF Scientific Retreat is a global scientific research conference that focuses on the most promising and interesting new research in the prostate cancer field, and topics arising from other fields that have the potential to impact and advance prostate cancer research and clinical care. The primary topic areas addressed at the 2019 PCF Retreat included: (i) new insights into prostate cancer biology and treatment; (ii) new drugs and drug targets in prostate cancer; (iii) advances in prostate cancer genomics; (iv) lessons from the multi-arm, multistage randomized phase 3 STAMPEDE trial; (v) advances in immunotherapy for prostate cancer; (vi) factors contributing to prostate cancer racial disparities; (vii) treatment-associated small-cell/neuroendocrine prostate cancer (t-SCNC); (viii) artificial intelligence and machine learning in cancer research and development; (ix) population science research on prostate cancer; and (x) prostate cancer research in the Department of Veterans Affairs. This article reviews the presentations from the 2019 PCF Scientific Retreat. We hope that this knowledge will accelerate research leading to new understandings of prostate cancer biology and improve treatments for patients with prostate cancer.

The Clinical Applications of Tissue Biomarkers in Prostate Cancer

The clinical course of localized prostate cancer varies widely, from indolent disease unlikely to need treatment to aggressive disease requiring intensive, multimodal therapy. Traditionally, treatment decisions have been based on clinical and pathologic factors, including serum prostate specific antigen (PSA), clinical stage, and Gleason score. However, these factors have limited ability to describe the underlying tumor biology. Tissue-based genomic tests have emerged as a promising tool to more accurately characterize prostate cancer biology and predict clinical course. Using prostate cancer tissue obtained at pre-treatment biopsy or radical prostatectomy, these tests exploit the expression of specific genes involved in key biological pathways and, as a result, have the potential to aid clinical decision-making. The current review summarizes available data describing the clinical use of 5 commercially available tissue-based genomic assays in a number of clinical scenarios.

Role of androgen receptor splice variant-7 (AR-V7) in prostate cancer resistance to 2nd-generation androgen receptor signaling inhibitors.

The role of truncated androgen receptor splice variant-7 (AR-V7) in prostate cancer biology is an unresolved question. Is it simply a marker of resistance to 2nd generation androgen receptor signaling inhibitors (ARSi) like Abiraterone Acetate (Abi) and Enzalutamide (Enza) or a functional driver of lethal resistance via its ligand-independent transcriptional activity? To resolve this question, the correlation between resistance to ARSi and genetic chances and expression of full length AR (AR-FL) vs. AR-V7 were evaluated in a series of independent patient-derived xenografts (PDXs). While all PDXs lack PTEN expression, there is no consistent requirement for mutation in TP53, RB1, BRCA2, PIK3CA, or MSH2, or expression of SOX2 or ERG and ARSi-resistance. Elevated expression of AR-FL alone is sufficient for Abi- but not Enza-resistance, even if AR-FL is gain-of-function (GOF) mutated. Enza-resistance is consistently correlated with enhanced AR-V7 expression. In vitro and in vivo growth responses of Abi-/Enza-resistant LNCaP-95 cells in which CRISPR-Cas9 was used to knockout AR-FL or AR-V7 alone or in combination were evaluated. Combining these growth responses with RNAseq analysis demonstrates that both AR-FL and AR-V7 dependent transcriptional complementation are needed for Abi/Enza resistance.

Expression of AR-V7 (Androgen Receptor Variant 7) Protein in Granular Cytoplasmic Structures Is an Independent Prognostic Factor in Prostate Cancer Patients.

Simple SummaryThe expression of the androgen receptor (AR) and its splice variant AR-V7 is crucial for prostate cancer (PCa) biology. An immunohistochemical staining was performed on a tissue microarray with specimens from 410 PCa patients. AR staining, neither in the nucleus nor in the cytoplasm was associated with prognosis. AR-V7 staining of the general cytoplasm was associated with a shorter relapse free survival (RFS), whereas AR-V7 staining of cytoplasmic granules was associated with a longer RFS. Further subgroup stratification for AR-V7 granular staining revealed it as an independent prognostic factor in younger patients (age ≤ 65), patients with negative CK20 staining and patients with perineural invasion. Altogether, AR-V7 protein detected in granular cytoplasmic structures is an independent prognostic factor for RFS in PCa patients.Prostate cancer (PCa) is the second most common cancer, causing morbidity and mortality among men world-wide. The expression of the androgen receptor (AR) and its splice variants is a crucial factor of prostate cancer biology that has not been comprehensively studied in PCa tumors. The aim of this study was to characterize the protein expression of the AR and its splice variant, AR-V7, and their subcellular distributions in PCa by immunohistochemistry and to correlate the results to the clinicopathological data and prognosis. Immunohistochemical staining for AR and AR-V7 was performed on a tissue microarray (TMA) with specimens from 410 PCa patients using an immunoreactive score (IRS) or only the percentage of AR-V7 staining in cytoplasmic granules. Nuclear or cytoplasmic AR staining was not associated with prognosis. AR-V7 staining was only occasionally observed in the nucleus. However, AR-V7 staining in the cytoplasm or in cytoplasmic granules was associated with relapse-free survival (RFS). AR-V7 staining of the cytoplasm was associated with a shorter RFS, whereas AR-V7 staining of cytoplasmic granules was associated with a longer RFS. In a multivariate Cox’s regression analysis, only negative (<5%) AR-V7 staining of cytoplasmic granules remained an independent prognostic factor for RFS (HR = 5.3; p = 0.006). In a further subgroup analysis by multivariate Cox’s regression analysis, AR-V7 was an independent prognostic factor in the following groups: age ≤ 65 (HR = 9.7; p = 0.029), negative CK20 staining (HR = 7.0; p = 0.008), and positive perineural invasion (HR = 3.7; p = 0.034). Altogether, AR-V7 protein in granular cytoplasmic structures is an independent prognostic factor for RFS in PCa patients.

Abstract 1114: Novel preclinical models of aggressive variants of castration-resistant prostate cancer

Abstract Background: Recent advances in the biology of prostate cancer have identified aggressive variants of metastatic castration-resistant prostate cancer [mCRPC] (e.g, CRPC with neuroendocrine (NE) features, or microsatellite instability [MSI], or BRCA2 mutations). However, few preclinical models have been successfully established to study these aggressive mCRPC variants owing to their historically low establishment success and to the difficulty in accessing such clinical samples Methods: Fresh tumor biopsy specimens were obtained prospectively from patients with mCRPC through a prospective single-institution clinical trial (MATCH-R, NCT02517892). Patient-derived xenografts (PDX) in NOD Scid Gamma mice were developed and characterized as well as PDX-derived organoids derived from the same PDX (PDXO). Whole-exome sequencing, RNA sequencing and immunohistochemistry were performed on human samples and their corresponding PDX and PDXO. The primary aim was to successfully derive PDX and PDXO models reproducing the clinical features of mCRPC aggressive variants. Results: As of November 2019, 83 tumor biopsies were obtained from 61 mCRPC patients, 16 biopsies from 13 patients were successfully engrafted with an overall success rate of 26% (16/61). In addition, 16 PDXO were developed with a success rate of 100%. Overall, we developed 4 PDX and 4 PDXO from 2 patients with germline BRCA2 mutation, 2 PDX and 2 PDXO from 1 patient with MSI-high CPRC, 10 PDX and 6 PDXO from 10 patients with NE mCPRC. Molecular profiling revealed a high concordance between PDX, PDXO and human tumor samples for histological phenotype, driver mutations and transcriptomic phenotypes. The two models harbouring BRCA2 mutation were highly sensitive to both carboplatin and olaparib (in PDX and PDXO) reflecting the clinical scenario observed in the patients. BRCA2-mutated PDX models were treated in vivo to derive olaparib-resistant mCRPC models. Genetic analysis identified secondary mutations restoring the reading-frame of the gene which reversed the sensitivity of the PDX to carboplatin and olaparib. Preclinical models derived from mCRPC with NE features (including the case of small cell carcinoma) globally reproduced the clinical patterns seen in human samples. Results from high-throughput organoid drug screening suggest good concordance with patients clinical response Conclusion: The study demonstrated the feasibility of establishing preclinical models (PDX and PDXO) derived from aggressive mCRPC variants. Overall, our models reproduce the phenotypic, molecular and pharmacological characteristics of their initial human samples and may represent a unique preclinical platform modeling BRCA2 mutated, MSI and neuroendocrine prostate cancers. Citation Format: Ludovic Bigot, Jonathan Sabio, Tony Ibrahim, Naoual Menssouri, Loic poiraudeau, Carole Helissey, Jean-Yves Scoazec, Zahira Merabet, Thierry De Baere, Frederic Deschamps, Maud Ngocamus, Claudio Nicotra, Etienne Rouleau, Ludovic Lacroix, Olivier Deas, Luc Friboulet, Gilles Vassal, Eric Solary, Jean-Charles Soria, Karim Fizazi, Fabrice André, Christophe Massard, Benjamin Besse, Yohann Loriot. Novel preclinical models of aggressive variants of castration-resistant 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 1114.

Abstract 5443: Modulating plasticity in aggressive variant prostate cancers

Abstract Aggressive Variant Prostate Cancers (AVPC) are a clinically and molecularly distinct subset of prostate cancers with a poor prognosis characterized by androgen-indifference, platinum-sensitivity and combined defects in Tp53, RB1 and PTEN, for which novel therapeutic approaches are urgently needed. Defects observed in these tumor suppressor pathways have been linked to lineage plasticity in genetically engineered mouse models. We hypothesized that this plasticity can be identified in human tumor samples, and can be modulated to serve as the foundation for effective combination therapies for the AVPC subset. We previously defined a gene expression signature derived from mouse embryonic day 6.5 that is representative of extensive cellular plasticity (PMID:26123483). We determined the plasticity scores in 12 patient-derived xenograft (PDX) models representative of the spectrum of prostate cancer biology (using available RNA sequencing profiles), and in 26 macrodissected tumor biopsies obtained from patients who received platinum-based chemotherapy for aggressive prostate cancer (using ALMAC Affymetrix gene expression microarray). As expected, the AVPC PDX models exhibited high plasticity scores as did 11 (42.3%) of the patient samples, associated with patient progression free- and overall survival. We next treated a well characterized AVPC PDX model (144-4) with the anti-EMT drug (p38MAPK inhibitor) SB203580 at 10mg/kg, and observed a decrease in stem-cell and EMT factors associated with plasticity. These data confirm the association between plasticity and AVPC in human tumor samples, and suggest that changes in plasticity can be measured in tumor samples to determine the value of its modulation in clinical trials. Acknowledgments: ALMAC Diagnostics Services, UK, and UTMDACC ATGC Core Lab (CCSG-CA016672-ATGC) for RNA sequencing services; UTMDACC Prostate Cancer SPORE (RS, SAM, AA), UTMDACC IRG (RS), and the UTMDACC Prostate Cancer Moonshot Program (AA) for financial support. Citation Format: Rama Soundararajan, Petra den Hollander, Peter Shepherd, Nora Navone, Daniele Lorenzini, Caddie Laberiano-Fernandez, Wei Lu, Jianling Zhou, Jingjing Liu, Jianhua Zhang, Luisa Maren Solis-Soto, Sendurai A. Mani, Ana Aparicio. Modulating plasticity in aggressive variant prostate cancers [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 5443.

Abstract 3446: High-resolution mapping of human prostate tumors- guiding better risk stratification and therapeutic approaches

Abstract Why this research is important Clinical care for localized prostate cancer in 2019 is primarily guided by a system of risk stratification that has remained unchanged for decades (PSA, tumor T-stage, Gleason grade). True advances are needed in: (1) risk stratification among primary tumors and (2) novel mechanistically rational approaches to tumors that pose the greatest clinical threat of metastatic progression. The primary prostate tumor is remarkably complex, consisting not only of tumor cells but also of extracellular matrix, vasculature, stromal cells and infiltrating immune cells. Most systemic therapies simply target the androgen receptor, a mainstay of prostate cancer therapy. Novel therapeutic targets would benefit patients with high-risk localized tumors and potentially patients with currently incurable metastatic disease. What we aim to accomplish We aim to understand, through the single-cell lens, the differences in the prostate tumor microenvironment across the spectrum of Gleason grades to identify novel cellular and molecular targets for therapeutic intervention. On the path to discovery The design of novel therapies against prostate cancer relies on a deep understanding of the identity and function of each cell type within the tumor microenvironment. Our interdisciplinary team of clinicians, surgeons, bioinformaticians and biologists will characterize changes in the cellular composition, state, and function within the prostate tumor microenvironment across the spectrum of surgical stages and grades. These efforts are largely driven by advances in single-cell sequencing and imaging technologies. Using single-cell RNA sequencing (scRNA-seq), we created the cellular anatomy of the prostate tumor and their matched-normal glandular tissues (19 patients; Gleason 6-10; T-stage 2a to 3b). We constructed an atlas comprised of ~70,000 non-erythroid viable cells collected from treatment-naïve primary prostate cancer specimens and ~75,000 cells from the matched normal prostate tissue. Analysis of transcriptional states revealed a complex tumor microenvironment, including immune cells and supporting non-immune stroma. Our analysis has allowed us to 1) create the cell-atlas of prostate tissue, 2) characterize heterogeneity of intratumoral cells of both lymphoid and myeloid cell lineages and 3) identify tumor heterogeneity among patients. We identify 8 clusters of myeloid cells and 14 clusters of lymphoid cells. A broad survey of both lineages revealed different functional states for the different clusters. Gene expression analysis will be combined with Slide- seq - a new technique that preserves the tumor architecture. Future impact of our research Our research will advance our understanding of prostate cancer biology with dual downstream goals of honing our prognostic algorithms and identifying new avenues of therapeutic intervention. Ultimately, our goal is to improve the quality and length of life of patients diagnosed with prostate cancer. Citation Format: Taghreed Hirz, Shenglin Mei, Youmna Kfoury, Chin-Lee Wu, Douglas M. Dahl, Philip Saylor, Peter Kharchenko, Ninib Baryawno, David Sykes. High-resolution mapping of human prostate tumors- guiding better risk stratification and therapeutic approaches [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 3446.

Prostate cancer reactivates developmental epigenomic programs during metastatic progression.

Epigenetic processes govern prostate cancer (PCa) biology, as evidenced by the dependency of PCa cells on the androgen receptor (AR), a prostate master transcription factor. We generated 268 epigenomic datasets spanning two state transitions-from normal prostate epithelium to localized PCa to metastases-in specimens derived from human tissue. We discovered that reprogrammed AR sites in metastatic PCa are not created de novo; rather, they are prepopulated by the transcription factors FOXA1 and HOXB13 in normal prostate epithelium. Reprogrammed regulatory elements commissioned in metastatic disease hijack latent developmental programs, accessing sites that are implicated in prostate organogenesis. Analysis of reactivated regulatory elements enabled the identification and functional validation of previously unknown metastasis-specific enhancers at HOXB13, FOXA1 and NKX3-1. Finally, we observed that prostate lineage-specific regulatory elements were strongly associated with PCa risk heritability and somatic mutation density. Examining prostate biology through an epigenomic lens is fundamental for understanding the mechanisms underlying tumor progression.

MicroRNAs as Guardians of the Prostate: Those Who Stand before Cancer. What Do We Really Know about the Role of microRNAs in Prostate Biology?

Prostate cancer is the second leading cause of cancer-related deaths of men in the Western world. Despite recent advancement in genomics, transcriptomics and proteomics to understand prostate cancer biology and disease progression, castration resistant metastatic prostate cancer remains a major clinical challenge and often becomes incurable. MicroRNAs (miRNAs), about 22-nucleotide-long non-coding RNAs, are a group of regulatory molecules that mainly work through post-transcriptional gene silencing via translational repression. Expression analysis studies have revealed that miRNAs are aberrantly expressed in cancers and have been recognized as regulators of prostate cancer progression. In this critical review, we provide an analysis of reported miRNA functions and conflicting studies as they relate to expression levels of specific miRNAs and prostate cancer progression; oncogenic and/or tumor suppressor roles; androgen receptor signaling; epithelial plasticity; and the current status of diagnostic and therapeutic applications. This review focuses on select miRNAs, highly expressed in normal and cancer tissue, to emphasize the current obstacles faced in utilizing miRNA data for significant impacts on prostate cancer therapeutics.