Androgen Deprivation Therapy Resistance Research Articles

Single cell and spatial transcriptomics highlight the interaction of club-like cells with immunosuppressive myeloid cells in prostate cancer

Prostate cancer treatment resistance is a significant challenge facing the field. Genomic and transcriptomic profiling have partially elucidated the mechanisms through which cancer cells escape treatment, but their relation toward the tumor microenvironment (TME) remains elusive. Here we present a comprehensive transcriptomic landscape of the prostate TME at multiple points in the standard treatment timeline employing single-cell RNA-sequencing and spatial transcriptomics data from 120 patients. We identify club-like cells as a key epithelial cell subtype that acts as an interface between the prostate and the immune system. Tissue areas enriched with club-like cells have depleted androgen signaling and upregulated expression of luminal progenitor cell markers. Club-like cells display a senescence-associated secretory phenotype and their presence is linked to increased polymorphonuclear myeloid-derived suppressor cell (PMN-MDSC) activity. Our results indicate that club-like cells are associated with myeloid inflammation previously linked to androgen deprivation therapy resistance, providing a rationale for their therapeutic targeting.

Adrenal-Permissive Germline HSD3B1 Allele and Prostate Cancer Outcomes

The adrenal androgen-metabolizing 3β-hydroxysteroid dehydrogenase-1 enzyme, encoded by the HSD3B1 gene, catalyzes the rate-limiting step necessary for synthesizing nontesticular testosterone and dihydrotestosterone production. The common adrenal-permissive HSD3B1(1245C) allele is responsible for encoding the 3β-HSD1 protein with decreased susceptibility to degradation resulting in higher extragonadal androgen synthesis. Retrospective studies have suggested an association of the HSD3B1 adrenal-permissive homozygous genotype with androgen deprivation therapy resistance in prostate cancer. To evaluate differences in mortality outcomes by HSD3B1 genetic status among men with prostate cancer. This cohort study of patients with prostate cancer who were enrolled in the Million Veteran Program within the Veterans Health Administration (VHA) system between 2011 and 2023 collected genotyping and phenotyping information. HSD3B1 genotype status was categorized as AA (homozygous adrenal-restrictive), AC (heterozygous adrenal-restrictive), or CC (homozygous adrenal-permissive). The primary outcome of this study was prostate cancer-specific mortality (PCSM), defined as the time from diagnosis to death from prostate cancer, censored at the date of last VHA follow-up. Secondary outcomes included incidence of metastases and PCSM in predefined subgroups. Of the 5287 participants (median [IQR] age, 69 [64-74] years), 402 (7.6%) had the CC genotype, 1970 (37.3%) had the AC genotype, and 2915 (55.1%) had the AA genotype. Overall, the primary cause of death for 91 patients (1.7%) was prostate cancer. Cumulative incidence of PCSM at 5 years after prostate cancer diagnosis was higher among men with the CC genotype (4.0%; 95% CI, 1.7%-6.2%) compared with the AC genotype (2.1%; 95% CI, 1.3%-2.8%) and AA genotype (1.9%; 95% CI, 1.3%-2.4%) (P = .02). In the 619 patients who developed metastatic disease at any time, the cumulative incidence of PCSM at 5 years was higher among patients with the CC genotype (36.0%; 95% CI, 16.7%-50.8%) compared with the AC genotype (17.9%; 95% CI, 10.5%-24.7%) and AA genotype (18.5%; 95% CI, 12.0%-24.6%) (P = .01). In this cohort study of US veterans undergoing treatment for prostate cancer at the VHA, the HSD3B1 CC genotype was associated with inferior outcomes. The HSD3B1 biomarker may help identify patients who may benefit from therapeutic targeting of 3β-hydroxysteroid dehydrogenase-1 and the androgen-signaling axis.

Emerging Trends of Nanomedicines in the Management of Prostate Cancer: Perspectives and Potential Applications.

Prostate cancer is one of the most life-threatening disorders that occur in males. It has now become the third most common disease all over the world, and emerging cases and spiking mortality rates are becoming more challenging day by day. Several approaches have been used to treat prostate cancer, including surgery, radiation therapy, chemotherapy, etc. These are painful and invasive ways of treatment. Primarily, chemotherapy has been associated with numerous drawbacks restricting its further application. The majority of prostate cancers have the potential to become castration-resistant. Prostate cancer cells exhibit resistance to chemotherapy, resistance to radiation, ADT (androgen-deprivation therapy) resistance, and immune stiffness as a result of activating tumor-promoting signaling pathways and developing resistance to various treatment modalities. Nanomedicines such as liposomes, nanoparticles, branched dendrimers, carbon nanotubes, and quantum dots are promising disease management techniques in this context. Nanomedicines can target the drugs to the target site and enhance the drug's action for a prolonged period. They may also increase the solubility and bioavailability of poorly soluble drugs. This review summarizes the current data on nanomedicines for the prevention and treatment of prostate cancer. Thus, nanomedicine is pioneering in disease management.

Abstract B004: Genomic loss of TP53 impairs AR-targeted activity in metastatic prostate cancer

Abstract Background: Metastatic prostate cancer (mPC) is notable for a spectrum of recurrent genomic alterations, some associated with overall prognosis and others predicting response to specific therapeutics. Standard mPC interventions are designed to suppress the signaling program regulated by the androgen receptor (AR). These include androgen deprivation therapy (ADT) to reduce AR ligand levels and AR signaling inhibitors (ARSI) that directly impair AR function. While ADT and ARSI produce clinical responses in most patients, the duration and depth of response vary greatly. In addition, specific recurring genomic alterations are associated with shorter responses after ADT and ARSI therapy. Among these are mutations and/or genomic copy loss involving key tumor suppressor genes, including PTEN, RB1 and TP53. However, the mechanistic contribution of TP53 loss to AR signaling and resistance to AR pathway-directed therapy remains unresolved. Methods: Isogenic prostate cancer cell lines with intact and TP53 deletions were constructed using CRISPR/Cas9. The transcriptome profiles were determined by RNA-seq, and ChIP-seq was used to determine the chromatin landscapes of AR localization. In addition, we performed ATAC-seq to assess chromatin accessibility. Finally, to further validate the findings, we comprehensively analyzed AR-regulated gene expression and AR cistromes across a panel of patient-derived xenograft (PDX) models and clinical cohorts of mPC patient samples with respect to TP53 status. Results: Compared to TP53-wild-type (WT) cells, the transcriptional results of isogenic knockout TP53 lines showed impaired AR canonical activity. However, the downregulated AR response pathway is not caused by reduced levels of AR transcript or protein levels. Additionally, a similar trend was also found while comparing TP53-WT PDX models with TP53-loss models. We found that the loss of TP53 can shift the chromatin binding of AR, and the altered AR binding sites correlated with genes involved in neurogenesis pathways, which provide a potential mechanism of how the loss of TP53 might impact AR signaling and promote ADT and ARSI treatment resistance. We also identified additional AR chromatin binding sites that were enriched due to the loss of TP53. The targets potentially regulated by these sites are involved in multiple pathways, including cell morphogenesis involved in differentiation and response to the endogenous stimulus. Conclusions and Future Directions: Overall, the results indicate that in addition to altering DNA damage and repair pathways and contributing to cancer progression, genetic loss of TP53 in mPC may directly impair ADT and ARSI therapies, partially through alteration of AR chromatin activity. In addition, the AR cistrome reprogramming resulting from TP53 loss could also affect other pathways that could be exploited to overcome ARSI treatment resistance. Citation Format: Wanting Han, Michael D. Nyquist, Ilsa Coleman, Navonil De Sarkar, Lisa Ang, Eva Corey, Peter S. Nelson. Genomic loss of TP53 impairs AR-targeted activity in metastatic 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 B004.

Abstract A077: MicroRNA drivers of resistance to androgen deprivation therapy in prostate cancer

Abstract INTRODUCTION: Prostate cancer is the most prevalent malignancy affecting Western males. It is initially an androgen-dependent disease: androgens bind to the androgen receptor and drive expression of genes that promote proliferation and evasion of apoptosis. Despite reduced androgen dependence in advanced prostate cancer, androgen receptor signalling remains a key driver of growth. Androgen deprivation therapy (ADT) is therefore a first line treatment approach and works well initially, but resistance inevitably develops. Abiraterone and Enzalutamide are drugs widely used in ADT and are androgen synthesis and androgen receptor signalling inhibitors respectively. The shortage of other treatment options means acquired resistance to these drugs is a major clinical problem. MicroRNAs (miRs) are important mediators of post-transcriptional gene regulation and show altered expression in cancer. Several have been linked to the development of resistance to ADT. Manipulation of such miRs may be a pathway to breakthrough treatments for advanced prostate cancer. This study aimed to validate ADT resistance-implicated miRs and their clinically relevant targets. MATERIALS AND METHODS: Small RNA-sequencing of Abiraterone- and Enzalutamide-resistant C42 prostate cancer cells identified subsets of miRs dysregulated as compared to parental cells. Real-Time Quantitative Reverse Transcription PCR (qRT-PCR) was used to validate altered expression of candidate ADT resistance-implicated miRs 195-5p, 497-5p and 29a-5p in ADT-resistant and -responsive prostate cancer cell lines, patient-derived xenografts (PDXs) and primary prostate cancer explants. RESULTS AND DISCUSSION: This study suggests a possible role for miR-497-5p in the development of ADT resistance in prostate cancer. MiR-497-5p expression was increased in ADT-resistant versus ADT-responsive prostate cancer cells. Importantly, miR-497-5p expression was also increased in Enzalutamide-treated, castrated (ADT-mimicking) PDXs versus intact PDXs. MiR-195-5p was also elevated in ADT-resistant versus -responsive prostate cancer cells, while there was a drop in miR-29a-5p expression. Candidate clinically relevant targets of miR-497-5p in prostate cancer were identified by mining AGO-PAR-CLIP-seq data sets and may include AVL9 and FZD6. CONCLUSION: In summary, this study identified microRNAs that are implicated in prostate cancer resistance to androgen deprivation therapy and could represent novel therapeutic targets for advanced disease. Citation Format: Philippa C. Saunders, Claire Fletcher. MicroRNA drivers of resistance to androgen deprivation therapy in 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 A077.

Abstract B008: Tumor-stromal 3D co-cultures to study the role of cancer-associated fibroblasts in the acquisition of androgen-deprivation therapy resistance in prostate cancer

Abstract Introduction and Objective Several studies have shown that cancer-associated fibroblasts (CAFs), the most abundant component in prostate cancer (PCa) microenvironment, promote resistance to androgen deprivation therapies, and metastatic development. The aim of this study is to elucidate the mechanisms of CAF-induced therapy resistance through the establishment of in vitro 3D co-cultures. Methods In this study, the androgen-dependent PNPCa patient-derived xenograft (PDX) model (derived from soft tissue metastasis), and the androgen-independent LAPC9 PDX model (bone metastasis) are used. Epithelial and stromal cells (human and mouse origin, respectively) are separated through magnetic-associated cell sorting to generate PDX-derived organoids and fibroblasts. Fibroblast RNA and protein expression is assessed through RT-qPCR, Western Blot, and Immunofluorescence. Direct 3D co-cultures are obtained by combining fluorescently labelled organoids and fibroblasts in ultra-low attachment plates in defined media. In indirect co-cultures, organoids are cultured in Spherical Plates (Kugelmeiers) with fibroblasts on transwell inserts. Organoid viability is measured after 9 days by CellTiter-Glo 3D Assay. Results PDX-derived fibroblasts express typical CAF genes (e.g. α-smooth muscle actin and Tenascin C), and androgen receptor (AR), both at RNA and protein level. AR protein expression (as well as RNA expression of the AR target gene Fkbp5) is increased in CAFs upon treatment with dyhydrotestosterone (DHT) 10nM, while co-treatment with the AR inhibitor Enzalutamide 10mM abrogates this effect, suggestive of functional AR signaling. These CAFs can organize into tumor/CAF organoid 3D structures upon combination with PDX-derived tumor epithelial cells, providing an in vitro functional model to study tumor-stromal interactions. In indirect (transwell) co-cultures, CAFs increase the viability of the androgen dependent PNPCa organoids, but not that of androgen independent LAPC9. This growth-promoting effect is observed even upon culturing of PNPCa organoids in non-optimal growth conditions, at low DHT concentrations (DHT 0.5nM and 0.25nM versus the standard DHT 1nM). The factors mediating this process will be identified by gene expression profiling of CAFs and organoids in transwell co-cultures and/or monoculture. Conclusions Our data indicate that PCa metastatic cells modify the properties of neighbor stromal cells to support tumorigenesis, since PDX-derived fibroblasts, originally part of the mouse dermal stroma, display CAF features and active AR signaling. 3D co-cultures represent a useful tool to study the tumor-stromal interactions. Our transwell co-culture experiments suggest that CAFs play an important role in supporting the viability and growth of early metastatic androgen dependent PCa cells (PNPCa) by secreting pro-tumorigenic factors. The possibility that CAFs exert different effects depending on the tumor stage setting (early vs advanced) will be subsequently investigated. Citation Format: Francesco Bonollo, Natalie Sampson, George Thalmann, Sofia Karkampouna, Marianna Kruithof-de Julio. Tumor-stromal 3D co-cultures to study the role of cancer-associated fibroblasts in the acquisition of androgen-deprivation therapy resistance in 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 B008.

Identification of bicalutamide resistance-related genes and prognosis prediction in patients with prostate cancer.

Prostate cancer (PCa) is the second most common type of cancer and the fifth leading cause of cancer-related death in men. Androgen deprivation therapy (ADT) has become the first-line therapy for inhibiting PCa progression; however, nearly all patients receiving ADT eventually progress to castrate-resistant prostate cancer. Therefore, this study aimed to identify hub genes related to bicalutamide resistance in PCa and provide new insights into endocrine therapy resistance. The data were obtained from public databases. Weighted correlation network analysis was used to identify the gene modules related to bicalutamide resistance, and the relationship between the samples and disease-free survival was analyzed. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed, and hub genes were identified. The LASSO algorithm was used to develop a bicalutamide resistance prognostic model in patients with PCa, which was then verified. Finally, we analyzed the tumor mutational heterogeneity and immune microenvironment in both groups. Two drug resistance gene modules were identified. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses revealed that both modules are involved in RNA splicing. The protein-protein interaction network identified 10 hub genes in the brown module LUC7L3, SNRNP70, PRPF3, LUC7L, CLASRP, CLK1, CLK2, U2AF1L4, NXF1, and THOC1) and 13 in the yellow module (PNN, PPWD1, SRRM2, DHX35, DMTF1, SALL4, MTA1, HDAC7, PHC1, ACIN1, HNRNPH1, DDX17, and HDAC6). The prognostic model composed of RNF207, REC8, DFNB59, HOXA2, EPOR, PILRB, LSMEM1, TCIRG1, ABTB1, ZNF276, ZNF540, and DPY19L2 could effectively predict patient prognosis. Genomic analysis revealed that the high- and low-risk groups had different mutation maps. Immune infiltration analysis showed a statistically significant difference in immune infiltration between the high- and low-risk groups, and that the high-risk group may benefit from immunotherapy. In this study, bicalutamide resistance genes and hub genes were identified in PCa, a risk model for predicting the prognosis of patients with PCa was constructed, and the tumor mutation heterogeneity and immune infiltration in high- and low-risk groups were analyzed. These findings offer new insights into ADT resistance targets and prognostic prediction in patients with PCa.

Induction of promyelocytic leukemia zinc finger protein by miR-200c-3p restores sensitivity to anti-androgen therapy in androgen-refractory prostate cancer and inhibits the cancer progression via down-regulation of integrin α3β4.

Androgen-refractory prostate cancer (ARPC) is one of the aggressive human cancers with metastatic capacity and resistance to androgen deprivation therapy (ADT). The present study investigated the genes responsible for ARPC progression and ADT resistance, and their regulatory mechanisms. Transcriptome analysis, co-immunoprecipitation, confocal microscopy, and FACS analysis were performed to determine differentially-expressed genes, integrin α3β4 heterodimer, and cancer stem cell (CSC) population. miRNA array, 3'-UTR reporter assay, ChIP assay, qPCR, and immunoblotting were used to determine differentially-expressed microRNAs, their binding to integrin transcripts, and gene expressions. A xenograft tumor model was used to assess tumor growth and metastasis. Metastatic ARPC cell lines (PC-3 and DU145) exhibiting significant downregulation of ZBTB16 and AR showed significantly upregulated ITGA3 and ITGB4. Silencing either one of the integrin α3β4 heterodimer significantly suppressed ARPC survival and CSC population. miRNA array and 3'-UTR reporter assay revealed that miR-200c-3p, the most strongly downregulated miRNA in ARPCs, directly bound to 3'-UTR of ITGA3 and ITGB4 to inhibit the gene expression. Concurrently, miR-200c-3p also increased PLZF expression, which, in turn, inhibited integrin α3β4 expression. Combination treatment with miR-200c-3p mimic and AR inhibitor enzalutamide showed synergistic inhibitory effects on ARPC cell survival in vitro and tumour growth and metastasis of ARPC xenografts in vivo, and the combination effect was greater than the mimic alone. This study demonstrated that miR-200c-3p treatment of ARPC is a promising therapeutic approach to restore the sensitivity to anti-androgen therapy and inhibit tumor growth and metastasis.

Targeting PKLR/MYCN/ROMO1 signaling suppresses neuroendocrine differentiation of castration-resistant prostate cancer

Conventional treatment of prostate cancer (PCa) uses androgen-deprivation therapy (ADT) to inhibit androgen receptor (AR) signaling-driven tumor progression. ADT-induced PCa recurrence may progress to an AR-negative phenotype with neuroendocrine (NE) histologic features, which are associated with metabolic disturbances and poor prognoses. However, the metabolic pathways that regulate NE differentiation (NED) in PCa remain unclear. Herein, we show a regulatory mechanism in NED-associated metabolism dysfunction induced by ADT, whereby overexpression of pyruvate kinase L/R (PKLR) mediates oxidative stress through upregulation of reactive oxygen species modulator 1 (ROMO1), thereby promoting NED and aggressiveness. ADT mediates the nuclear translocation of PKLR, which binds to the MYCN/MAX complex to upregulate ROMO1 and NE-related genes, leading to altered mitochondrial function and NED of PCa. Targeting nuclear PKLR/MYCN using bromodomain and extra-terminal motif (BET) inhibitors has the potential to reduce PKLR/MYCN-driven NED. Abundant ROMO1 in serum samples may provide prognostic information in patients with ADT. Our results suggest that ADT resistance leads to upregulation of PKLR/MYCN/ROMO1 signaling, which may drive metabolic reprogramming and NED in PCa. We further show that increased abundance of serum ROMO1 may be associated with the development of NE-like PCa.

Gankyrin-mediated interaction between cancer cells and tumor-associated macrophages facilitates prostate cancer progression and androgen deprivation therapy resistance

ABSTRACT Increasing evidence reveals that the interaction between tumor cells and tumor-associated macrophages (TAMs) facilitates the progression of prostate cancer, but the related mechanisms remained unclear. This study determined how gankyrin, a component of the 19S regulatory complex of the 26S proteasome, regulates the progression and androgen deprivation therapy (ADT) resistance of prostate cancer through tumor cell–TAM interactions. In vitro functional experiments and in vivo subcutaneous tumor models were used to explore the biological role and molecular mechanisms of gankyrin in prostate cancer cell–TAM interactions. 234 prostate cancer patients were randomly divided into training and validation cohorts to examine the prognostic value of gankyrin through immunohistochemistry (IHC) and statistical analyses, and high gankyrin expression was correlated with poor prognosis. In addition, gankyrin facilitated the progression and ADT resistance of prostate cancer. Mechanistically, gankyrin recruited and upregulated non–POU-domain–containing octamer-binding protein (NONO) expression, resulting in increased androgen receptor (AR) expression. AR then bound to the high-mobility group box 1 (HMGB1) promoter to trigger HMGB1 transcription, expression, and secretion. Moreover, HMGB1 was found to promote the recruitment and activation of TAMs, which secrete IL-6 to reciprocally promote prostate cancer progression, ADT resistance and gankyrin expression via STAT3, resulting in formation of a gankyrin/NONO/AR/HMGB1/IL-6/STAT3 positive feedback loop. Furthermore, targeting the interaction between tumor cells and TAMs by blocking this loop inhibited ADT resistance in a tumor xenograft model. Taken together, the data show that gankyrin serves as a reliable prognostic indicator and therapeutic target for prostate cancer patients.

Simultaneous administration of EZH2 and BET inhibitors inhibits proliferation and clonogenic ability of metastatic prostate cancer cells

Androgen deprivation therapy (ADT) is a common treatment for recurrent prostate cancer (PC). However, after a certain period of responsiveness, ADT resistance occurs virtually in all patients and the disease progresses to lethal metastatic castration-resistant prostate cancer (mCRPC). Aberrant expression and function of the epigenetic modifiers EZH2 and BET over activates c-myc, an oncogenic transcription factor critically contributing to mCRPC. In the present work, we tested, for the first time, the combination of an EZH2 inhibitor with a BET inhibitor in metastatic PC cells. The combination outperformed single drugs in inhibiting cell viability, cell proliferation and clonogenic ability, and concomitantly reduced both c-myc and NF-kB expression. Although these promising results will warrant further in vivo validation, they represent the first step to establishing the rationale that the proposed combination might be suitable for mCRPC treatment, by exploiting molecular targets different from androgen receptor.

Epigenetic (De)regulation in Prostate Cancer.

Prostate cancer (PCa) is a heterogeneous disease exhibiting both genetic and epigenetic deregulations. Epigenetic alterations are defined as changes not based on DNA sequence, which include those of DNA methylation, histone modification, and chromatin remodeling. Androgen receptor (AR) is the main driver for PCa and androgen deprivation therapy (ADT) remains a backbone treatment for patients with PCa; however, ADT resistance almost inevitably occurs and advanced diseases develop termed castration-resistant PCa (CRPC), due to both genetic and epigenetic changes. Due to the reversible nature of epigenetic modifications, inhibitors targeting epigenetic factors have become promising anti-cancer agents. In this chapter, we focus on recent studies about the dysregulation of epigenetic regulators crucially involved in the initiation, development, and progression of PCa and discuss the potential use of inhibitors targeting epigenetic modifiers for treatment of advanced PCa.

Expression of high molecular weight cytokeratin-A novel feature of aggressive and innate hormone-refractory prostatic adenocarcinoma.

Castration-resistance is common in advanced prostatic adenocarcinomas (PACs) treated with androgen deprivation therapy (ADT) and usually occurs after 2 years following treatment. A minority of PACs confer innate ADT resistance without prior hormonal treatment. The expression of HMWCK in PAC cells has not been studied. This study aimed to investigate the clinicopathologic and genomic features of HMWCK-expressing PACs and the relationship to ADT resistance. A total of 469 PACs were studied for HMWCK expression (39 postradiotherapy, 57 post-ADT, 373 treatment-naïve PACs). Clinicopathologic correlations of the HMWCK expression with tumor grade groups, specific tumor morphologies, tumor stages and disease recurrence/persistence/progression were performed. Five HMWCK+ PACs were also sequenced for genetic alterations. Thirty one of the 469 cases (6.6%) showed variable HMWCK+ PAC. The HMWCK+ PAC often focally presented in the tumor and vast majority were associated with high Gleason scores and unfavorable growth patterns (cribriform, comedo-necrosis, and intraductal carcinoma) as well as high tumor stages. A small percentage of the HMWCK+ PCA (2/31, 6.5%) presented with frank squamous histomorphology. Vast majority (22/31, 87%) had no history of prior ADT. The HMWCK+ PAC all displayed diminished to lost expression of AR/NKX3.1. Most of the cases progressed within 12 months of ADT or disease persisted despite ADT. Of the 5 HMWCK+ PACs subjected to gene sequencing, 4 presented with PTEN/PI3K/MAPK pathway alterations. The study demonstrated HMWCK+ PAC to be a novel type of innate ADT-resistant PAC. Overexpression of HMWCK in PAC can be potentially used as a surrogate biomarker for aggressive and innate hormone-refractory PACs. The genetic alterations imply potential therapeutic implications of PI3K/MAPK inhibitors in the treatment of these deadly diseases.

Second generation anti-androgens and androgen deprivation therapy with radiation therapy in the definitive management of high-risk prostate cancer.

Evolving data suggest that men with high-risk localized prostate cancer may benefit from more potent androgen receptor inhibition in the context of curative intent radiotherapy. Recently updated American Society for Clinical Oncology (ASCO) evidence-based guidelines and the National Comprehensive Cancer Network (NCCN) Guidelines have updated recommendations for the consideration of adding second generation anti-androgens to androgen deprivation therapy (ADT) in men receiving radiation therapy (RT) for noncastrate locally advanced high and very high risk nonmetastatic or node positive prostate cancer. We conducted a comprehensive review of existing published and abstract presented evidence behind RT with ADT for the definitive management of high-risk prostate cancer, particularly focused on the current phase II and III trial evidence for the addition of second generation anti-androgens to ADT in definitive RT treatment of high-risk prostate cancer and specifically focused on the recent STAMPEDE trial results with abiraterone acetate. We review the biological mechanisms in which second generation anti-androgens may help mitigate ADT resistance and provide radiosensitization through inhibition of DNA repair. Finally, we discuss ongoing clinical trials of potent androgen receptor (AR) inhibitors with ADT in this non-metastatic high-risk radiotherapy setting that may inform on future treatment guidelines. Recent data suggest an overall survival benefit as well as increased probabilities of disease free and metastasis free survival in men with high and very high-risk localized, node positive, and oligometastatic hormone sensitive prostate cancer with abiraterone acetate and prednisone and support the use of potent AR inhibitors in this setting after informed decision making.

Prostate tumor RON receptor signaling mediates macrophage recruitment to drive androgen deprivation therapy resistance through Gas6-mediated Axl and RON signaling.

Androgen deprivation therapy (ADT), or chemical castration, is the first-line therapy for prostate cancer; however, resistance leaves few treatment options. Prostatic tumor-associated macrophages (TAMs) have been shown to promote prostate cancer growth and are abundant in castration-resistant prostate cancer (CRPC), suggesting a role in promoting CRPC. We recently showed a tumor cell-intrinsic mechanism by which RON promotes CRPC. Given previous reports that RON alters prostate cancer cell chemokine productionand RON-overexpressing tumors alter macrophage function, we hypothesized that a macrophage-dependent mechanism regulated by tumor cell intrinsic RON also promotes CRPC. Using RON-modulated genetically engineered mouse models (GEMMs) and GEMM-derived cell lines and co-cultures with bone marrow-derived macrophages, we show functional and molecular characteristics of signaling pathways in supporting CRPC. Further, we used an unbiased phosphokinase array to identify pathway interactions regulated by RON. Finally, using human prostate cancer cell lines and prostate cancer patient data sets, we show the relevance of our findings to human prostate cancer. Studies herein show that macrophages recruited into the prostate tumor microenvironment (TME) serve as a source for Gas6 secretion which serves to further enhance RON and Axl receptor activation in prostate tumor cells thereby driving CRPC. Further, we show targeting RON and macrophages in a murine model promotes CRPC sensitization to ADT. We discovered a novel role for the RON receptor in prostate cancer cells in promoting CRPC through the recruitment of macrophages into the prostate TME. Macrophage-targeting agents in combination with RON/Axl inhibition are likely to provide clinical benefits for patients with CRPC.

Abstract 397: Mesenchymal stem cell-derived systemic NRG-1 mediates a targetable molecular switch in metastatic prostate cancer

Abstract NRG-1 signals through epidermal growth factor receptor (EGFR) family members. Despite promising preclinical data, HER2 blockade in prostate cancer has failed to improve outcomes in clinical trials.1-4 We have discovered a novel complex systemic role of NRG-1 that drives sensitivity and resistance to androgen deprivation therapy (ADT) in castration-sensitive (CSPC) and castration resistant prostate cancer (CRPC), respectively. Significantly, sensitivity to ADT can be restored in CRPC by manipulating NRG-1 signaling. Our data posit NRG-1 as a systemic “switch” in prostate cancer. Plasma NRG-1 is elevated in our cohort of patients with metastatic CRPC (mean 4.9ng/ml) versus healthy controls (mean 3.2ng/ml, p<0.0001) or metastatic CSPC (mean 3.4ng/ml, p<0.0001). Paradoxically, high systemic NRG-1 predicted superior OS and PFS in CSPC but inferior clinical outcomes in CRPC. Consistently, opposite cell survival between LNCaP (CSPC) vs Du145 & PC3 (CRPC) was observed with recombinant human NRG-1 and enzalutamide (ENZ). ENZ combined with increasing NRG-1 concentration induced LNCaP cell death in an additive manner, but NRG-1 rescued Du145 & PC3 from ENZ-induced death in a dose-dependent manner. We next hypothesized that differential NRG-1 downstream signaling is mediated by engagement with distinct EGFR receptor dimers. While HER2 expression is similar, LNCaP express higher HER3 than Du145 & PC3. High ratio of HER2 to HER3 in Du145 & PC3 mirrors clinical reports of HER2 upregulation in CRPC5,6 and also predicts patient survival in the Stand Up to Cancer cohort.7 Significantly, we recapitulated the CRPC phenotype in LNCaP by inducing HER2 overexpression, HER3 suppression, and chemically-mediated HER2/HER3 dimerization. Conversely, HER2 knockdown sensitized Du145 cells to ENZ. Next, we queried composite single-cell whole human8 and CRPC9 transcriptomes for NRG-1 expression and discovered that the source of NRG-1 is the patients’ own mesenchymal stem cells (MSCs). Bone-derived MSC outgrowth cells produced copious NRG-1, which was increased substantially by coincubation with prostate cancer cell supernatants. Importantly, we were able to manipulate MSCs to reduce their NRG-1 production as a possible clinical translation. Similarly, patients treated with these compounds showed significant reduction in plasma NRG-1 levels after treatment. Additional clinical studies are pending. Together, our observations confirm that NRG-1 has differential signaling: HER3 homodimerization leads to prostate cancer cell death, whereas heterodimerization of HER3 with HER2 leads to prostate cancer cell survival via ADT resistance in a plasma NRG-1 dependent manner. Consequently, HER2 and HER3 receptor availability determine the molecular switch of NRG-1 in prostate cancer. Therefore, NRG-1 can be both a prognostic marker and therapeutic target in CRPC, and multiple clinical trials are pending. Citation Format: Jacob Orme, Roman Thaler, Dejie Wang, Siven Chinniah, Jacob Hirdler, Fernando Quevedo, Lance Pagliaro, Kwon Eugene, Alan Bryce, Brian Costello, Haojie Huang, Sean Park. Mesenchymal stem cell-derived systemic NRG-1 mediates a targetable molecular switch in metastatic prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 397.

Hypoxia-Reoxygenation Couples 3βHSD1 Enzyme and Cofactor Upregulation to Facilitate Androgen Biosynthesis and Hormone Therapy Resistance in Prostate Cancer.

Hypoxia followed by reoxygenation in prostate cancer drives androgen deprivation therapy resistance via increasing the rate-limiting enzyme and cofactors for androgen synthesis, revealing HIF2α as a therapeutic target to subvert resistance.

Tumor microenvironment mechanisms and bone metastatic disease progression of prostate cancer

During disease progression from primary towards metastatic prostate cancer (PCa), and in particular bone metastases, the tumor microenvironment (TME) evolves in parallel with the cancer clones, altering extracellular matrix composition (ECM), vasculature architecture, and recruiting specialized tumor-supporting cells that favor tumor spread and colonization at distant sites. We introduce the clinical profile of advanced metastatic PCa in terms of common genetic alterations. Findings from recently developed models of PCa metastatic spread are discussed, focusing mainly on the role of the TME (mainly matrix and fibroblast cell types), at distinct stages: premetastatic niche orchestrated by the primary tumor towards the metastatic site and bone metastasis. We report evidence of premetastatic niche formation, such as the mechanisms of distant site conditioning by extracellular vesicles, chemokines and other tumor-derived mechanisms, including altered cancer cell-ECM interactions. Furthermore, evidence supporting the similarities of stroma alterations among the primary PCa and bone metastasis, and contribution of TME to androgen deprivation therapy resistance are also discussed. We summarize the available bone metastasis transgenic mouse models of PCa from a perspective of pro-metastatic TME alterations during disease progression and give an update on the current diagnostic and therapeutic radiological strategies for bone metastasis clinical management.

THEM6‐mediated reprogramming of lipid metabolism supports treatment resistance in prostate cancer

Despite the clinical benefit of androgen‐deprivation therapy (ADT), the majority of patients with advanced prostate cancer (PCa) ultimately develop lethal castration‐resistant prostate cancer (CRPC). In this study, we identified thioesterase superfamily member 6 (THEM6) as a marker of ADT resistance in PCa. THEM6 deletion reduces in vivo tumour growth and restores castration sensitivity in orthograft models of CRPC. Mechanistically, we show that the ER membrane‐associated protein THEM6 regulates intracellular levels of ether lipids and is essential to trigger the induction of the ER stress response (UPR). Consequently, THEM6 loss in CRPC cells significantly alters ER function, reducing de novo sterol biosynthesis and preventing lipid‐mediated activation of ATF4. Finally, we demonstrate that high THEM6 expression is associated with poor survival and correlates with high levels of UPR activation in PCa patients. Altogether, our results highlight THEM6 as a novel driver of therapy resistance in PCa as well as a promising target for the treatment of CRPC.

Gankyrin-Mediated Interaction between Cancer Cells and Tumor-Associated Macrophages Facilitates Prostate Cancer Progression and Androgen Deprivation Therapy Resistance

Gankyrin-Mediated Interaction between Cancer Cells and Tumor-Associated Macrophages Facilitates Prostate Cancer Progression and Androgen Deprivation Therapy Resistance