Small Cell Neuroendocrine Prostate Cancer Research Articles

Somatostatin receptor 1 (SSTR1) expression as a potential predictive biomarker for response to androgen receptor signaling inhibitor (ARSI) therapy in metastatic castration-resistant prostate cancer (mCRPC).

180 Background: Overcoming ARSI resistance is an unmet need for mCRPC patients. Known resistance mechanisms include genetic alterations augmenting androgen receptor (AR) function (e.g., amplifications of the AR gene and its enhancer and AR mutations) and treatment-emergent evolution from an AR-driven to an AR-indifferent phenotype such as small cell neuroendocrine prostate cancer. Other mechanisms remain unexplored. Methods: To phenotype ARSI-resistant prostate cancer, we compared the RNA-seq profiles of paired metastatic biopsies from 31 mCRPC patients obtained before the initiation of first-line abiraterone or enzalutamide, and upon radiographic progression. The patient samples were obtained from two independent cohorts, the Stand Up To Cancer/Prostate Cancer Foundation (SU2C/PCF) West Coast Prostate Cancer Dream Team (WCDT) and a multi-institutional cohort from the Netherlands sequenced through the Hartwig Medical Foundation. We first evaluated RNA-seq data to identify the most differentially expressed genes and then performed survival analysis in the retrospective WCDT cohort (n=115, including 54 ARSI-naïve and 61 ARSI-experienced tumors) to assess the association between gene expression and overall survival, defined as the time interval from biopsy to death from any cause. Results: In the analysis of paired RNA-seq data from 31 mCRPC patients, SSTR1 was identified as the most significantly altered gene; SSTR1 expression was consistently decreased in post-treatment, ARSI-resistant tumors (log2[fold change]=-2.5, p=1.08×10-16). SSTR1 encodes somatostatin receptor 1, a G-protein coupled receptor that, when activated by the endogenous peptide hormone somatostatin or exogenous somatostatin analogues, mediates anti-proliferative, anti-migratory, and anti-secretory effects on target cells. Retrospective analysis in the 115 WCDT patients demonstrated that low SSTR1 expression was associated with worse overall survival ( p=0.047); ARSI treatment improved survival for patients with SSTR1-high (≥ median) tumors (HR=0.29, p=0.0002) more significantly than those with SSTR1-low (< median) tumors (HR=0.67, p=0.17), with an interaction ( SSTR1 expression * ARSI treatment) towards statistical significance ( p=0.0598). A differential survival benefit of ARSI therapy with respect to SSTR1 expression was observed only among the 61 ARSI-experienced patients. Conclusions: SSTR1 expression is a potential predictive biomarker for response to ARSI in mCRPC, with higher SSTR1 expression predicting better response. This observation could be explained by an anti-tumor effect of SSTR1 signaling. Further work is warranted to prospectively validate these findings and to investigate SSTR1 as an actionable drug target to overcome ARSI resistance.

Diagnostic role and prognostic impact of PSAP immunohistochemistry: A tissue microarray study on 31,358 cancer tissues from 127 different tumor types

Abstract Introduction/Objective Prostatic specific acid phosphatase (PSAP) protein is produced in prostate epithelial cells and it is used as an immunohistochemical marker for prostate cancer. However, studies have reported PSAP expression to occur in various other tumor entities as well. Methods/Case Report Prostatic specific acid phosphatase (PSAP) protein is produced in prostate epithelial cells and it is used as an immunohistochemical marker for prostate cancer. However, studies have reported PSAP expression to occur in various other tumor entities as well. Results (if a Case Study enter NA) In prostate cancer, PSAP staining was seen in 100% of Gleason 3 + 3, 95.5% Gleason 4 + 4, 93.8% recurrent prostate cancer under androgen deprivation therapy, 91.0% Gleason 5 + 5 and 31.2% small cell neuroendocrine prostate cancer. Reduced PSAP staining was strongly linked to high pT stage, high Gleason grade, lymph node metastasis, early PSA-recurrence (p<0.0001 each),high androgen receptor expression and TMPRSS2:ERG fusions. In multivariate analyses, low PSAP expression was able to predict PSA recurrence independent of pre- and postoperative prognostic markers in ERG negative cancers. In extra-prostatic cancers, PSAP immunostaining was only seen in 3 of 94 (3.2%) neuroendocrine tumors of the pancreas and in 1 of 129 (0.8%) diffuse type gastric adenocarcinomas. Conclusion A positive PSAP immunostaining is highly specific for prostate cancer and reduced PSAP expression is associated with an aggressive prostate cancer phenotype. The independent association of reduced PSAP expression with poor prognosis in ERG negative prostate cancer makes PSAP measurement a candidate marker for prognostic multiparameter panels for prostate cancer.

Abstract B017: Lineage-specific PRC2 targets and response to EZH2 inhibition in neuroendocrine prostate cancer

Abstract Lineage plasticity is an emerging mechanism of treatment-resistance in prostate cancer, which can manifest clinically as histologic transformation from prostate adenocarcinoma to small-cell neuroendocrine prostate cancer (NEPC). NEPC is associated with poor prognosis, and new treatment strategies are urgently needed. Epigenetic dysregulation has been implicated as a key driver of prostate cancer lineage plasticity, mediated in part by EZH2. EZH2 is a component of the polycomb repressive complex (PRC2) regulating the transcriptional repressive mark H3K27me3. EZH2 also controls cell-fate determination during normal development via bivalent promoters bearing both repressive H3K27me3 and active H3K4me3 marks. EZH2 is targetable, and several EZH2 inhibitors are in clinical development; these trials are currently in biomarker-unselected prostate cancer populations. A thorough understanding of the mechanism of action of EZH2 is imperative for predicting optimal response to EZH2i and for the development of robust combination treatment strategies. Cell viability studies across a diverse panel of prostate cancer models representing adenocarcinoma and NEPC indicated variable responses to tazemetostat (EZH2i) treatment. The castration-resistant prostate adenocarcinoma (CRPC) cell line LNCaP-abl showed a greater than 50% reduction in cell viability upon EZH2i (5uM) while LNCaP and 22Rv1 showed moderate response with 15-25% reduction in cell viability. However, none of our 5 NEPC patient-derived models showed significant response to EZH2i which was also validated in vivo. Hierarchical clustering of RNA-seq profiles of responder and non-responder models revealed distinct cell-type specific EZH2 targets and clusters of genes that may be associated with response to EZH2i. Approximately 15% of the EZH2 targets in the NEPC organoid WCM154 carried bivalency in their promoters including neuronal lineage determining genes such as ASCL1 and LHX2. Gene set enrichment analysis of EZH2 targets bearing bivalency in NEPC revealed association with neurogenesis and cell proliferation pathways. Further upregulation of neuronal-lineage PRC2 targets in NEPC models upon EZH2i may provide justification for lack of lineage reversal and maintenance of terminal differentiation. While there is evidence that EZH2i leads to lineage reversion in adeno-to-NEPC transitioning preclinical models, our data shows that EZH2i was associated with modest response in NEPC models and did not revert lineage plasticity. Our results provide insights into a potential role for bivalent promoters in EZH2-mediated lineage reprogramming and sustenance of terminal differentiation upon EZH2i in NEPC. Understanding lineage-specific action of EZH2i may inform biomarkers in ongoing clinical trials. Genes and pathways dysregulated because of their bivalency might also be exploited as potential candidates to be co-targeted with EZH2i. Citation Format: Varadha Balaji Venkadakrishnan, Richa Singh, Yasutaka Yamada, Kei Mizuno, Adam G. Presser, Sheng-Yu Ku, Henry Long, David Rickman, Himisha Beltran. Lineage-specific PRC2 targets and response to EZH2 inhibition in neuroendocrine prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B017.

Primary adrenal insufficiency in the context of small-cell neuroendocrine prostate cancer

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Treatment outcome after sequential chemotherapy with cisplatin-etoposide, amrubicin and nogitecan in patients with treatment-related pure small-cell neuroendocrine prostate cancer.

This study retrospectively reviewed the clinical characteristics and treatment outcomes of patients with histologically diagnosed treatment-related pure small-cell neuroendocrine prostate cancer. We retrospectively evaluated data for 13 patients with treatment-related neuroendocrine prostate cancer who were diagnosed between May 2015 and February 2022. Standardized systemic therapies of etoposide plus cisplatin (or carboplatin), amrubicin and nogitecan were selected as sequential treatments. Cancer-specific survival and progression-free survival were evaluated as the primary endpoint. The Cox proportional hazards model was used to evaluate the relationships between treatment regimens, clinical variables, cancer-specific survival and progression-free survival. The median cancer-specific survival after diagnosis for all patients was 22.4months (range 1.3-33.4months). The median progression-free survival was 9.3months after first-line etoposide plus cisplatin (or carboplatin) treatment (n=13); 4.2months after second-line amrubicin treatment (n=4); and>15months after third-line nogitecan treatment (n=2). The median progression-free survival after first-line chemotherapy of the liver metastasis (-) group was 10.2months, and that of the (+) group was 5.3months (P=0.015, hazard ratio=11.6, 95% confidence interval=1.01-133.7). No clinicopathological parameters were identified as significant independent predictors of cancer-specific survival in univariate analysis. Sequential chemotherapy with etoposide plus cisplatin (or carboplatin), amrubicin and nogitecan may be helpful for patients with treatment-related pure small-cell neuroendocrine prostate cancer. Early biopsy of metastases and initiation of effective therapy is essential for patients with progressive castration-resistant prostate cancer and low prostate-specific antigen.

Immunotherapeutic Targeting and PET Imaging of DLL3 in Small-Cell Neuroendocrine Prostate Cancer.

The preclinical and clinical evaluation of DLL3-directed immunotherapy, AMG 757, and development of a PET radiotracer for noninvasive DLL3 detection demonstrate the potential of targeting DLL3 in SCNC prostate cancer.

Dynamic plasticity of prostate cancer intermediate cells during androgen receptor-targeted therapy.

Treatment-emergent small cell neuroendocrine prostate cancer (t-SCNC) is associated with an epithelial lineage switch from an androgen receptor (AR)-positive to neuroendocrine (NE)-marker-positive status. Understanding the potential for reversibility of this aggressive disease state has been hampered by the paucity of models suitable for studying rate-limiting, transitional, or intermediate tumor cell subpopulations. We define a dual reporter model that measures acute transcriptional changes in response to castration or AR targeting agents. We identify steady-state transcriptional heterogeneity in AR and NE biomarkers, including intermediate subpopulations that are coordinately high for prostate-specific antigen (PSA) and neuron-specific enoclase (NSE) promoter activity. In the presence of castration or AR inhibitors, intermediate cells were necessary and sufficient for therapy-induced conversion of human PC cells to an NSE-high transcriptional status. Using hormone add-back studies, treatment-induced PSA-NSE transcriptional plasticity was reversible in PTEN-deficient PC cells but not in the presence of secondary genetic driver genes, including MYCN.

Biallelic loss of TP53, PTEN, and RB1 in association to aggressive clinical features and poor outcomes in metastatic castration-resistant prostate cancer (mCRPC).

5055 Background: Deleterious alterations in tumor suppressor genes (TSGs) TP53, RB1, and PTEN are potential markers of small cell neuroendocrine prostate cancer (SCNP), and androgen receptor pathway inhibitor (ARPI) resistance. We examined the outcomes and clinical features of mCRPC patients (pts) harboring biallelic loss in 0, 1, 2 or all 3 TSGs. Methods: We identified 210 consecutive mCRPC pts providing ≥1 plasma cell-free DNA sample with ≥20% circulating tumor DNA fraction (ctDNA%) during their mCRPC disease course. ctDNA% ≥20% enabled sensitive characterization of biallelic TSG loss (including by homozygous deletions and mutation plus somatic loss-of-heterozygosity; LOH). Patient records were reviewed for baseline characteristics, SCNP histology, and presence of liver metastases. We investigated associations between TSG loss and the following clinical outcomes: PSA response (PSA decline ≥50% (PSA50 RR)), progression free survival (PFS) on 1L therapy, and overall survival (OS) from 1L therapy. Results: Median follow-up was 16.5 months (range: 0.4-112.4) and OS event rate was 95%. Median age at 1L mCRPC was 71 years (range: 48-98). Most pts were ECOG PS 0-1 (79%) and 13% had liver metastases. 91% received ARPI for 1L mCRPC and 7% received ARPI for castration-sensitive disease. TP53 was primarily inactivated by somatic mutation plus LOH (90%), whereas RB1 (71%) and PTEN (86%) were more commonly inactivated by homozygous deletions. Compared to pts without evidence of biallelic TSG loss, pts with loss of 3 TSGs were significantly enriched for de-novo M1 disease (86 vs. 60%, p=0.05) and liver metastases (28.5 vs. 6.8%, p<0.05). Ten pts (4.7%) had histologically confirmed SCNP and provided ctDNA at time of SCNP diagnosis. Of these, 7 (70%) had biallelic loss of ≥2 TSGs. For all pts receiving 1L therapy, loss of ≥1 TSG(s) was associated with decreased OS (HR: 1.86, 95% CI: 1.40-2.48, p<0.01) and PFS (HR:1.74, 95% CI 1.29-2.34, p<0.01) compared to pts with no biallelic TSG loss. Furthermore, a cumulative increase in the number of TSGs lost was associated with an incremental reduction in OS and PFS (Table). Conclusions: In a cohort enriched for poor prognosis (i.e. high ctDNA%), cumulative loss of TSGs is associated with aggressive disease features and poor clinical outcomes. These patients may benefit from alternative treatment intensification strategies. [Table: see text]

TCF7L1 regulates cytokine response and neuroendocrine differentiation of prostate cancer

Neuroendocrine differentiation (NED) is associated with WNT signaling activation and can be significantly observed after failure of androgen-deprivation therapy (ADT) for prostatic adenocarcinomas. Cytokine signaling is stimulated in NED prostate cancer; however, how ADT-upregulated WNT signaling promotes activation of cytokine signaling and contributes to NED of prostate cancer is poorly understood. In this study, we identified ADT-mediated upregulation of transcription factor 7 like 1 (TCF7L1), which increases the cytokine response and enhances NED of prostate cancer through interleukin (IL)-8/C-X-C motif chemokine receptor type 2 (CXCR2) signaling activation. ADT induced the secretion of WNT4 which upon engagement of TCF7L1 in prostate cancer cells, enhanced IL-8 and CXCR2 expressions. TCF7L1 directly binds to the regulatory sequence region of IL-8 and CXCR2 through WNT4 activation, thus upregulating IL-8/CXCR2 signaling-driven NED and cell motility. Analysis of prostate tissue samples collected from small-cell neuroendocrine prostate cancer (SCPC) and castration-resistant prostate cancer (CRPC) tumors showed an increased intensity of nuclear TCF7L1 associated with CXCR2. Our results suggest that induction of WNT4/TCF7L1 results in increased NED and malignancy in prostate cancer that is linked to dysregulation of androgen receptor signaling and activation of the IL-8/CXCR2 pathway.

Prognosis Associated With Luminal and Basal Subtypes of Metastatic Prostate Cancer

Luminal and basal subtypes of primary prostate cancer have been shown to be molecularly distinct and clinically important in predicting response to therapy. These subtypes have not been described in metastatic prostate cancer. To identify clinical and molecular correlates of luminal and basal subtypes in metastatic castration-resistant prostate cancer (mCRPC) and investigate differences in survival, particularly after treatment with androgen-signaling inhibitors (ASIs). In this cohort study, a retrospective analysis was conducted of 4 cohorts with mCRPC (N = 634) across multiple academic centers. Treatment was at the physicians' discretion. Details of the study cohorts have been published elsewhere between 2016 and 2019. Data were analyzed from March 2018 to February 2021. The primary clinical end point was overall survival from the date of tissue biopsy/molecular profiling. Luminal and basal subtypes were also stratified by postbiopsy ASI treatment. The primary molecular analyses included associations with small cell/neuroendocrine prostate cancer (SCNC), molecular pathways, and DNA alterations. In the 634 patients, 288 (45%) had tumors classified as luminal, and 346 (55%) had tumors classified as basal. However, 53 of 59 (90%) SCNC tumors were basal (P < .001). Similar to primary prostate cancer, luminal tumors exhibited overexpression of AR pathway genes. In basal tumors, a significantly higher rate of RB1 loss (23% basal vs 4% luminal; P < .001), FOXA1 alterations (36% basal vs 27% luminal; P = .03) and MYC alterations (73% basal vs 56% luminal; P < .001) were identified. Patients with basal tumors had worse overall survival compared with those with luminal tumors only in patients treated with an ASI postbiopsy (East Coast Dream Team: hazard ratio [HR], 0.39; 95% CI, 0.20-0.74; P = .004; West Coast Dream Team: HR, 0.57; 95% CI, 0.33-0.97; P = .04). Among patients with luminal tumors, those treated with an ASI had significantly better survival (HR, 0.27; 95% CI, 0.14-0.53; P < .001), whereas patients with basal tumors did not (HR, 0.62; 95% CI, 0.36-1.04, P = .07). The interaction term between subtype and ASI treatment was statistically significant (HR, 0.42; 95% CI, 0.20-0.89; P = .02). These findings represent the largest integrated clinical, transcriptomic, and genomic analysis of mCRPC samples to date, and suggest that mCRPC can be classified as luminal and basal tumors. Analogous to primary prostate cancer, these data suggest that the benefit of ASI treatment is more pronounced in luminal tumors and support the use of ASIs in this population. In the basal tumors, a chemotherapeutic approach could be considered in some patients given the similarity to SCNC and the diminished benefit of ASI therapy. Further validation in prospective clinical trials is warranted.

Therapy considerations in neuroendocrine prostate cancer: what next?

Lineage plasticity and histologic transformation to small cell neuroendocrine prostate cancer (NEPC) is an increasingly recognized mechanism of treatment resistance in advanced prostate cancer. This is associated with aggressive clinical features and poor prognosis. Recent work has identified genomic, epigenomic, and transcriptome changes that distinguish NEPC from prostate adenocarcinoma, pointing to new mechanisms and therapeutic targets. Treatment-related NEPC arises clonally from prostate adenocarcinoma during the course of disease progression, retaining early genomic events and acquiring new molecular features that lead to tumor proliferation independent of androgen receptor activity, and ultimately demonstrating a lineage switch from a luminal prostate cancer phenotype to a small cell neuroendocrine carcinoma. Identifying the subset of prostate tumors most vulnerable to lineage plasticity and developing strategies for earlier detection and intervention for patients with NEPC may ultimately improve prognosis. Clinical trials focused on drug targeting of the lineage plasticity process and/or NEPC will require careful patient selection. Here, we review emerging targets and discuss biomarker considerations that may be informative for the design of future clinical studies.

Treatment-emergent neuroendocrine prostate cancer with a germline BRCA2 mutation: identification of a candidate reversion mutation associated with platinum/PARP-inhibitor resistance.

Neuroendocrine prostate cancer (NEPC) is a highly aggressive histologic subtype of prostate cancer associated with a poor prognosis. Its incidence is expected to increase as castration-resistant disease emerges from the widespread use of potent androgen receptor-targeting therapies, such as abiraterone and enzalutamide. Defects in homologous recombination repair genes, such as BRCA1/2, are also being increasingly detected in individuals with advanced prostate cancer. We present the case of a 65-yr-old man with a germline BRCA2 mutation who developed explosive treatment-emergent, small-cell neuroendocrine prostate cancer. He achieved a complete response to platinum-containing chemotherapy, but a limited remission duration with the use of olaparib, a poly(ADP-ribose) polymerase (PARP) inhibitor, as maintenance therapy. Upon relapse, tumor genomic profiling revealed a novel 228-bp deletion in exon 11 of the BRCA2 gene. The addition of the anti-PD1 drug pembrolizumab to olaparib was ineffective. This case highlights the ongoing challenges in treating neuroendocrine prostate cancer, even in the setting of homologous recombination repair deficiency.

Nerve growth factor interacts with CHRM4 and promotes neuroendocrine differentiation of prostate cancer and castration resistance

Nerve growth factor (NGF) contributes to the progression of malignancy. However, the functional role and regulatory mechanisms of NGF in the development of neuroendocrine prostate cancer (NEPC) are unclear. Here, we show that an androgen-deprivation therapy (ADT)-stimulated transcription factor, ZBTB46, upregulated NGF via ZBTB46 mediated-transcriptional activation of NGF. NGF regulates NEPC differentiation by physically interacting with a G-protein-coupled receptor, cholinergic receptor muscarinic 4 (CHRM4), after ADT. Pharmacologic NGF blockade and NGF knockdown markedly inhibited CHRM4-mediated NEPC differentiation and AKT-MYCN signaling activation. CHRM4 stimulation was associated with ADT resistance and was significantly correlated with increased NGF in high-grade and small-cell neuroendocrine prostate cancer (SCNC) patient samples. Our results reveal a role of the NGF in the development of NEPC that is linked to ZBTB46 upregulation and CHRM4 accumulation. Our study provides evidence that the NGF-CHRM4 axis has potential to be considered as a therapeutic target to impair NEPC progression.

Dynamic Plasticity of Prostate Cancer Intermediate Cells During Androgen Receptor Targeted Therapy

The prevalence of treatment induced small cell neuroendocrine prostate cancer (t-SCNC) is increasing due to the extended use of potent AR signaling inhibitors. Understanding the kinetics and potential for reversibility of t-SCNC progression has been hampered by the lack of model systems suitable for studying intermediate tumor cell states. Here, we define a transcriptional reporter model that provides dynamic measures of treatment induced changes in human prostate cancer cell subpopulations. With this system we have identified intermediate tumor cells, defined as double high in expression for prostate specific antigen (PSA) and neuron specific enolase (NSE) expression. This tumor cell subpopulation functions as a necessary and sufficient component for the cellular conversion to an NE transcriptional signature when under the selective pressure of androgen ablation or AR signaling inhibitors. Such transcriptional plasticity was found to be reversible in a hormone and genetic driver dependent manner. Our data provide novel and mechanistic in site for understanding the contribution of transition cell populations to the emergence of therapeutic resistance in advanced castration resistant prostate cancer (CRPC).

Abstract 3083: Selective inhibition of transcription factor BRN2 as a treatment strategy for Small Cell Prostate Cancer

Abstract Introduction: Resistance to newly developed androgen receptor pathway inhibitors (ARPIs), such as Enzalutamide (ENZ), rapidly emerges. In particular, a subset of patients who relapse following ARPI therapy their dependence on AR signaling and emerge with neuroendocrine features. These tumors, termed treatment induced small-cell prostate cancer (t-SCPC) or neuroendocrine prostate cancer (t-NEPC), carry an extremely poor prognosis and, to date, treatment remains decades old cytotoxic chemotherapies. Previously, our group identified the neural transcription factor BRN2 as a major clinically relevant driver of SCPC and now report that targeting BRN2 is a promising strategy to prevent neuroendocrine differentiation or treat NEPC.Methods/Results: In silico screening of small molecules was conducted on a model of BRN2 which was later validated with the first-in-field crystal structure of BRN2 DNA binding domain. On the basis of the model, several small molecules were identified that showed direct binding to BRN2 and inhibited its activity. Pharmacokinetic studies measured stability and bioavailability of med-chem optimized lead compound (BRN2i) that significantly reduced tumor growth in multiple xenograft models with no measurable side-effects. In silico modeling predicted a 7Å “closing” in the DBD once it was bound to BRN2i, this shift translated to reduced interaction with DNA by chromatin fractionation and ChIP-seq, thus confirming the mode of action for BRN2i is through loss of DNA binding. Loss of BRN2 binding reduced cell proliferation in tSCPC cell line 42DENZR, de novo SCPC cell line NCI-H660 and NEPC organoids as well as downregulated several known targets like EZH2, ASCL1, SOX2 and PEG10. Down-regulation of these target genes was also measured in the xenograft tumors, confirming on target effect in vivo. Moreover, the specificity of BRN2i was validated with CRISPR/Cas9 mediated knockout of BRN2 with downstream mRNA expression and phenotypic changes. Conclusion: The described work aims to lay the pre-clinical foundation for the integration of BRN2 targeted therapies into the treatment landscape to improve survival for patients suffering from small-cell neuroendocrine prostate cancer. Citation Format: Daksh Thaper, Ravi Munuganti, Adeleke Aguda, Soojin Kim, Shungyu Ku, Sahil Kumar, Sepideh Vahid, Shaghayegh Nouruzi, Olena Sivak, Dwaiyapan Ganguli, Colm Morrissey, Eva Corey, Himisha Beltran, Amina Zoubeidi. Selective inhibition of transcription factor BRN2 as a treatment strategy for Small Cell 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 3083.

Specificities of small cell neuroendocrine prostate cancer: Adverse prognostic value of TTF1 expression

ObjectivesTo determine whether small cell neuroendocrine prostate cancers (NEPCa) emerging after anti-androgen treatments are different from the rarest cases diagnosed de novo, and to identify effective predictive markers. Material and methodsThe expression of neuroendocrine markers, androgen receptor (AR) and androgen-regulated genes, as well as markers of aggressiveness, were analyzed by immunohistochemistry on a tissue microarray containing samples of 30 sNEPCa, either pure or admixed with conventional PCa, and including 14 cases diagnosed de novo and 16 cases subsequent to prior androgen deprivation. ResultsChromogranin A is a better marker of NE differentiation than synaptophysin in post-treatment NEPCa, with 94% and 44% of positive tumors, respectively, while both markers are equally expressed in de novo cases. Despite the acquisition of a NE phenotype, more than half of NEPCa expressed AR and the androgen-regulated gene NKX3.1, more frequently in cases admixed with conventional PCa. TTF1 staining, present in half of NEPCa, was associated with loss of androgen-regulated genes and with markers of aggressiveness, including increased proliferation, Zeb1 expression and PTEN loss. In multivariate analysis, only TTF1 expression was significantly associated with shorter overall survival. ConclusionThese results suggest the persistence of androgen signaling in a number of NEPCa cases, and the interest of TTF1 staining as a predictive biomarker.

Down-regulation of ADRB2 expression is associated with small cell neuroendocrine prostate cancer and adverse clinical outcomes in castration-resistant prostate cancer

ObjectivesThe net oncogenic effect of β2-adrenergic receptor ADRB2, whose downstream elements induce neuroendocrine differentiation and whose expression is regulated by EZH2, is unclear. ADRB2 expression and associated clinical outcomes in metastatic castration-resistant prostate cancer (mCRPC) are unknown. Methods and materialsThis was a retrospective analysis of a multi-center, prospectively enrolled cohort of mCRPC patients. Metastatic biopsies were obtained at progression, and specimens underwent laser capture microdissection and RNA-seq. ADRB2 expression was stratified by histology and clustering based on unsupervised hierarchical transcriptome analysis and correlated with EZH2 expression; an external dataset was used for validation. The association between ADRB2 expression and overall survival (OS) was assessed by log-rank test and a multivariable Cox proportional hazard model. ResultsOne hundred and twenty-seven patients with progressive mCRPC had sufficient metastatic tumor for RNA-seq. ADRB2 expression was lowest in the small cell-enriched transcriptional cluster (P < 0.01) and correlated inversely with EZH2 expression (r = -0.28, P < 0.01). These findings were validated in an external cohort enriched for neuroendocrine differentiation. Patients with tumors harboring low ADRB2 expression (lowest quartile) had a shorter median OS than those with higher (9.5 vs. 20.5 months, P = 0.02). In multivariable analysis, low ADRB2 expression was associated with a trend toward shorter OS (HR for death = 1.54, 95%CI 0.98–2.44). Conversely, higher expression of upstream transcriptional regulator EZH2 was associated with shortened OS (HR for death = 3.01, 95%CI 1.12–8.09). ConclusionsLow ADRB2 expression is associated with neuroendocrine differentiation and is associated with shortened survival. EZH2 is a potential therapeutic target for preventing neuroendocrine transdifferentiation and improving outcomes in mCRPC. Further studies of agents targeting β-adrenergic signaling are warranted.

Germline genetic mutational landscape and characteristics of men with prostate cancer (PCa): A single institution experience.

e13679 Background: The role of germline genetic testing (GGT) is rapidly changing for men with PCa. We describe the characteristics of men with PCa diagnosed with pathogenic (P) and likely pathogenic (LP) mutations on GGT. Methods: We conducted a retrospective single-institution study for all men with PCa who received single gene or multi-gene GGT from 1997-2019, unselected for disease stage, Gleason score, or age at diagnosis, and while most had a family history of cancer, some did not. All participants were from the Risk Assessment Program (RAP) database at FCCC and consented for research purposes at the time of GGT. Results: 160 men with PCa had GGT. 72/160 (45%) patients had no mutations. 41/160 (26%) patients had a variant of undetermined significance (VUS) (13 with 2 VUS, 1 with 3 VUS). 47/160 (29%) men were found to have a P or LP germline mutation. 26/47 (55%) with recurrent disease, and 1/47 (2%) unknown. 46 were Caucasian, and 1 was African American ( PALB2). 28/47 (60%) had Gleason Scores (GS) ≤7. 6/47 (13%) had a Prostate Specific Antigen (PSA) at diagnosis &lt; 4.0 ng/mL. 23/47 (49%) were diagnosed &lt; 60 years of age, and 8/47 (17%) at ≤ 50. 19/23 (83%) PCa cases with P/LP diagnosed below age 60 had DNA repair genes: BRCA2 (8), BRCA1 (4), CHEK2 (4), ATM (2), and PALB2 (1). 74/160 (46%) were tested after PCa NCCN genetics guidelines changed (October 2017), of which 19/74 (25%) had P/LP, and of those positive for P/LP, 6/19 (32%) had non-metastatic disease. Two patients had small cell neuroendocrine PCa ( CHEK2 and BRCA2), the remaining had adenocarcinoma PCa. Please see Table for full results. Conclusions: To our knowledge, this is the largest single-institution study reporting PCa characteristics and incidence of P/LP germline mutations. Rates of DNA-repair gene mutations were higher than previously reported, possibly reflecting our specialized cancer center’s population. While BRCA1/2 mutations were the most represented (55%), we describe PCa patients with mutations in ATM, CHEK2, NBN, PALB2, CFTR, and MUTYH, recognizing a few are not known to be linked to PCa. More than half of P/LP mutation carriers had GS ≤7. Additionally, 13% of the men with P/LP germline mutations had low PSA ( &lt; 4.0 ng/mL) at diagnosis. Our findings highlight the importance of the new guidelines and GGT importance in some men with PCa, particularly if they could benefit from a different therapeutic approach, or be influenced into cascade GGT. [Table: see text]

MP16-12 METHYLATION CAN REGULATE THE EXPRESSION OF PD-L1 IN SMALL CELL PROSTATE CANCER

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology I (MP16)1 Apr 2020MP16-12 METHYLATION CAN REGULATE THE EXPRESSION OF PD-L1 IN SMALL CELL PROSTATE CANCER Yi Sun*, Qiang Wei, Jiaoti Huang, and Lu Yang Yi Sun*Yi Sun* More articles by this author , Qiang WeiQiang Wei More articles by this author , Jiaoti HuangJiaoti Huang More articles by this author , and Lu YangLu Yang More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000000841.012AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: As a broad generality, programmed death-ligand 1 (PD-L1)–positive tumors tend to have a higher rate of objective response to PD-1/PD-L1 blockade, and PD-L1 expression remains an important clinically validated predictive biomarker for response, in addition, according to some published paper, the expression of PD-L1 is much higher in small cells neuroendocrine prostate cancer. So we focus on the mechanism of this phenomena. METHODS: We collect the human tissue samples and performed the Immunohistochemistry (IHC) stain to test the expression of PD-L1, and also use the Interferon-g (IFN-g) to treat some cells lines test the expression of PD-L1. Moreover, we also test the expression of PD-L1 in xenograft mice model treated by IFN-g. And then we test the expression and the activation of the whole IFN respond pass-way in human tissue samples, mice tumor samples and cell lines. To test the effect of JAK/STAT pass-way on this process, we block the JAK/STAT pass-way and then test the IFN respond again. And then we test the impact of methylation on the expression of JAK1 also the INF respond. RESULTS: The comprehensive evaluation of PD-L1 expression in prostate cancer showed that PD-L1 expression is rare in primary prostate cancers, but increased rates of PD-L1 positivity were observed in Small Cell Neuroendocrine (SCNE) prostate cancer. Similar results could be found in Small Cell Neuroendocrine Cancer (SCNC) cells and the SCNC mice model under the stimulation of IFN-g. Block the JAK1/STAT1 pass-way could drastically inhibit this process. The expression of JAK1 and this whole process also suppressed by demethylation. CONCLUSIONS: This study demonstrated that PD-L1 expression is much higher in a small cell prostate cancer. And the reason behind this phenomenon is the JAK/STAT pass-way regulated by methylation. Source of Funding: This study was supported by the National Natural Science Foundation of China (Grant No. 81370855, 81300627, 81702536, 81770756 and 81200551), This study was supported by the National key research and development program of China (Grant No. SQ2017YFSF090096), the Prostate Cancer Foundation Young Investigator Award 2013, Foundation of Science &Technology Department of Sichuan Province (Grant No. 2015SZ0230, 2013SZ0006 and 2013SZ0093), Programs from Science and Technology Department of Sichuan Province (Grant No. 2018JY0089 and 2017HH0063), Young Investigator Award of Sichuan University 2017, and the Scientific Research Project of Health Department of Sichuan Province (No. 120203). © 2020 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 203Issue Supplement 4April 2020Page: e219-e220 Advertisement Copyright & Permissions© 2020 by American Urological Association Education and Research, Inc.MetricsAuthor Information Yi Sun* More articles by this author Qiang Wei More articles by this author Jiaoti Huang More articles by this author Lu Yang More articles by this author Expand All Advertisement PDF downloadLoading ...

Identification of Therapeutic Vulnerabilities in Small-cell Neuroendocrine Prostate Cancer.

Small-cell neuroendocrine prostate cancer (SCNPC) exhibits an aggressive clinical course and incidence rates seem to be increasing following resistance to potent androgen receptor (AR) antagonists. Currently, treatment options are limited and few model systems are available to identify new approaches for treatment. We sought to evaluate commonalities between SCNPC and other aggressive neuroendocrine carcinomas to identify therapeutic targets. We generated whole transcriptome RNA-sequencing data from AR-active prostate cancers (ARPCs) and SCNPCs from tumors collected at rapid autopsy and two other neuroendocrine carcinomas, Merkel cell carcinoma (MCC), and small-cell lung cancer. We performed cross-tumor comparisons to identify conserved patterns of expression of druggable targets. We tested inhibitors to highly upregulated drug targets in a panel of prostate cancer cell lines and in vivo patient-derived xenograft (PDX) models. We identified BCL2 as highly upregulated in SCNPC compared with ARPC. Inhibitors targeting BCL2 induced apoptotic cell death in SCNPC cell lines at nanomolar concentrations while ARPC cell lines were resistant. Treatment with the BCL2 inhibitor navitoclax leads to a reduction of growth of SCNPC PDX tumors in vivo, whereas ARPC PDX models were more resistant. We identified Wee1 as a second druggable target upregulated in SCNPC. Treatment with the combination of navitoclax and the Wee1 inhibitor AZD-1775 repressed the growth of SCNPC PDX resistant to single-agent BCL2 inhibitors. The combination of BCL2 and Wee1 inhibition presents a novel therapeutic strategy for the treatment of SCNPC.