Prostate cancer-induced endothelial-cell-to-osteoblast transition drives immunosuppression in the bone-tumor microenvironment through Wnt pathway-induced M2 macrophage polarization.

Immune checkpoint therapy has limited efficacy for patients with bone-metastatic castration-resistant prostate cancer (bmCRPC). To improve immunotherapy for bmCRPC, we aimed to identify the mechanism of bmCRPC-induced changes in the immune microenvironment. Among bmCRPC patients, higher levels of a 32-gene M2-like macrophage signature in bone metastasis samples correlated with shorter overall survival. Immunohistochemistry showed that CD206-positive (CD206+) macrophages were enriched in bmCRPC bone biopsy specimens compared with primary tumors or lymph node metastases. In preclinical osteogenic prostate cancer (Pca) xenograft models, CD206+ macrophages were recruited to areas with tumor-induced bone. RNA sequencing (RNAseq) analysis showed higher expression of an M2-like gene signature, with activated canonical and noncanonical Wnt pathways, in tumor-associated macrophages isolated from osteogenic tumors (bone-TAMs) than in TAMs isolated from nonosteogenic tumors (ctrl-TAMs). Mechanistic studies showed that endothelial cells (ECs) that had undergone EC-to-osteoblast (EC-to-OSB) transition, the precursors of tumor-induced OSBs, produced paracrine factors, including Wnts, CXCL14, and lysyl oxidase, which induced M2 polarization and recruited M2-like TAMs to the bone-tumor microenvironment (bone-TME). Bone-TAMs suppressed CD8+ T cells' proliferation and cytolytic activity, and these effects were partially reversed by treating bone-TAMs with Wnt inhibitors. Genetic or pharmacological inhibition of Pca-induced EC-to-OSB transition reduced the levels of M2-like macrophages in osteogenic tumors. Our study demonstrates that Pca-induced EC-to-OSB transition drives immunosuppression in the bone-TME, suggesting that therapies that reduce Pca-induced bone formation may improve immunotherapeutic outcomes for bmCRPC.

Cabazitaxel plus carboplatin for the treatment of men with metastatic castration-resistant prostate cancers: a randomised, open-label, phase 1-2 trial.

BACKGROUND: Taxane-platinum combinations have shown promising activity in metastatic castration-resistant prostate cancers in single-group clinical studies but not in randomised trials. Distinct biological subsets of the disease might derive the greatest benefit from the addition of platinum. We aimed to determine whether adding carboplatin to cabazitaxel would improve the outcomes of men with metastatic castration-resistant prostate cancer. METHODS: We did a phase 1-2, open label, randomised study at two centres in men with progressive metastatic castration-resistant prostate cancer. In phase 1, patients received intravenous cabazitaxel 20-25 mg/m2 and intravenous carboplatin area under the curve (AUC) 3-4 mg/mL per min every 21 days. The maximum tolerated dose was defined as the highest dose cohort studied in which one of six or fewer patients experienced a dose-limiting toxicity. In phase 2, patients were randomly assigned (1:1) centrally by a computerised algorithm to intravenous cabazitaxel 25 mg/m2 with or without intravenous carboplatin AUC 4 mg/mL per min. All patients received growth factor support and oral prednisone 10 mg daily. The primary endpoints were the maximum tolerated dose of the combination in phase 1 and investigator-assessed progression-free survival in phase 2. This trial is registered at ClinicalTrials.gov, number NCT01505868. FINDINGS: Between Aug 17, 2012, and May 11, 2015, nine patients completed phase 1 as planned, and 160 were randomly assigned to cabazitaxel (n=79) or cabazitaxel plus carboplatin (n=81) in phase 2. During phase I, grade 3 adverse events were anaemia (n=2), fatigue (n=1), thrombocytopenia (n=1), hypomagnesaemia (n=1), diarrhoea (n=1), hypokalaemia (n=1), anorexia (n=1), and dehydration (n=1), and no grade 4 adverse events occurred. No dose-limiting toxicities were observed, therefore, a maximum tolerated dose of cabazitaxel of 25 mg/m2 and carboplatin of AUC 4 mg/mL per min was selected for phase 2. At a median follow-up of 31·0 months (IQR 20·5-37·1), the combination improved the median progression-free survival from 4·5 months (95% CI 3·5-5·7) to 7·3 months (95% CI 5·5-8·2; hazard ratio 0·69, 95% CI 0·50-0·95, p=0·018). In the phase 2 study, the most common grade 3-5 adverse events were fatigue (7 [9%] of 79 in the cabazitaxel group vs 16 [20%] of 81 in the combination group), anaemia (3 [4%] vs 19 [23%]), neutropenia (3 [4%] vs 13 [16%]), and thrombocytopenia (1 [1%] vs 11 [14%]). There were no treatment-related deaths. INTERPRETATION: Carboplatin added to cabazitaxel showed improved clinical efficacy compared with cabazitaxel alone for men with metastatic castration-resistant prostate cancer. Although adverse events were more common with the combination, the treatment was safe and generally well tolerated. Our data suggest that taxane-platinum combinations have a clinically beneficial role in advanced prostate cancer and a randomised phase 3 study is planned. FUNDING: Sanofi Genzyme, University of Texas MD Anderson Cancer Center Prostate Cancer Moon Shot Program, and Solon Scott III Prostate Cancer Research Fund.

The combination of serum insulin, osteopontin, and hepatocyte growth factor predicts time to castration-resistant progression in androgen dependent metastatic prostate cancer- an exploratory study.

BACKGROUND: We hypothesized that pretreatment serum levels of insulin and other serum markers would predict Progression-free survival (PFS), defined as time to castration-resistant progression or death, in metastatic androgen-dependent prostate cancer (mADPC). METHODS: Serum samples from treatment-naïve men participating in a randomized phase 3 trial of ADT +/- chemotherapy were retrospectively analyzed using multiplex assays for insulin and multiple other soluble factors. Cox proportional hazards regression models were used to identify associations between individual factor levels and PFS. RESULTS: Sixty six patients were evaluable (median age = 72 years; median prostate surface antigen [PSA] = 31.5 ng/mL; Caucasian = 86 %; Gleason score ≥8 = 77 %). In the univariable analysis, higher insulin (HR = 0.81 [0.67, 0.98] p = 0.03) and C-peptide (HR = 0.62 [0.39, 1.00]; p = 0.05) levels were associated with a longer PFS, while higher Hepatocyte Growth Factor (HGF; HR = 1.63 [1.06, 2.51] p = 0.03) and Osteopontin (OPN; HR = 1.56 [1.13, 2.15]; p = 0.01) levels were associated with a shorter PFS. In multivariable analysis, insulin below 2.1 (ln scale; HR = 2.55 [1.24, 5.23]; p = 0.011) and HGF above 8.9 (ln scale; HR = 2.67 [1.08, 3.70]; p = 0.027) levels were associated with longer PFS, while adjusted by OPN, C-peptide, trial therapy and metastatic volume. Four distinct risk groups were identified by counting the number of risk factors (RF) including low insulin, high HGF, high OPN levels, and low C-peptide levels (0, 1, 2, and 3). Median PFS was 9.8, 2.0, 1.6, and 0.7 years for each, respectively (p < 0.001). CONCLUSION: Pretreatment serum insulin, HGF, OPN, and C-peptide levels can predict PFS in men with mADPC treated with ADT. Risk groups based on these factors are superior predictors of PFS than each marker alone.

Prognosis of patients with metastatic renal cell carcinoma and pancreatic metastases.

OBJECTIVES: To identify the clinical outcomes of patients with metastatic renal cell carcinoma (mRCC) with pancreatic metastases (PM) treated with either pazopanib or sunitinib and assess whether PM is an independent prognostic variable in the current therapeutic environment. PATIENTS AND METHODS: A retrospective review of patients with mRCC in an outpatient clinic was carried out for the period January 2006 to November 2011. Patient characteristics, including demographics, laboratory data and outcomes, were analysed. Baseline characteristics were compared using chi-squared and t-tests and overall survival (OS) and cancer-specific survival (CSS) rates were estimated using Kaplan-Meier methods. Predictors of OS were analysed using Cox regression. RESULTS: A total of 228 patients were reviewed, of whom 44 (19.3%) had PM and 184 (81.7%) had metastases to sites other than the pancreas. The distribution of baseline characteristics was equal in both groups, with the exception of a higher incidence of previous nephrectomy, diabetes and number of metastatic sites in the PM group. Four patients had isolated PM, but the majority of patients (68%) with PM had at least three different organ sites of metastases, as compared with 29% in patients without PM (P < 0.01). The distribution of organ sites of metastases was similar, excluding the pancreas, in those with and those without PM (P > 0.05). The median OS was 39 months (95% confidence interval [CI] 24-57, hazard ratio 0.66, 95% CI 0.42-0.94; P = 0.02) for patients with PM, compared with 26 months (95% CI 21-31) for patients without PM (P < 0.01). CSS was 42 months (95% CI 30-57) in the PM group and 27 months (95% CI 22-33) in the control group (P = 0.05). CONCLUSIONS: Despite a higher number of affected organ sites in the PM cohort, mRCC behaviour in this cohort appears to be more indolent, as demonstrated by a higher median OS. These findings suggest that host or tumour features associated with PM may represent a less aggressive tumour phenotype.

Src signaling pathways in prostate cancer.

Knowledge of the molecular events that contribute to prostate cancer progression has created opportunities to develop novel therapy strategies. It is now well established that c-Src, a non-receptor tyrosine kinase, regulates a complex signaling network that drives the development of castrate-resistance and bone metastases, events that signal the lethal phenotype of advanced disease. Preclinical studies have established a role for c-Src and Src Family Kinases (SFKs) in proliferation, angiogenesis, invasion and bone metabolism, thus implicating Src signaling in both epithelial and stromal mechanisms of disease progression. A number of small molecule inhibitors of SFK now exist, many of which have demonstrated efficacy in preclinical models and several that have been tested in patients with metastatic castrate-resistant prostate cancer. These agents have demonstrated provocative clinic activity, particularly in modulating the bone microenvironment in a therapeutically favorable manner. Here, we review the discovery and basic biology of c-Src and further discuss the role of SFK inhibitors in the treatment of advanced prostate cancer.

Randomized phase 2 study of bone-targeted therapy containing strontium-89 in advanced castrate-sensitive prostate cancer.

BACKGROUND: Radiopharmaceutical use may improve the survival time of patients with castrate-resistant prostate cancer and bone metastases. Whether androgen-deprivation therapy (ADT) combined with bone-targeted therapy provides a clinical benefit to patients with advanced castrate-sensitive prostate cancer has not been investigated. METHODS: Eighty male patients were enrolled, and 79 were randomized: 40 to the control arm and 39 to the strontium-89 (Sr-89) arm. After randomization, patients in both study arms received ADT, doxorubicin, and zoledronic acid. Kaplan-Meier methodology was used to evaluate the progression-free survival (PFS) time. Multivariate Cox proportional hazards regression was used to evaluate the effects of Sr-89 after controlling for the number of bone metastases. RESULTS: The median follow-up time for the 29 patients alive at the last follow-up was 76.9 months (range, 0.07-103.4 months). The median PFS time was 18.5 months (95% confidence interval, 9.7-49.4 months) for the control arm and 12.9 months (95% confidence interval, 8.9-72.5 months) for the Sr-89 arm (P = .86). No patient developed myelodysplastic syndrome or a hematologic malignancy. An unplanned subgroup analysis suggested increased efficacy of bone-targeted therapy with a greater extent of bone involvement (ie, >6 bone metastases vs ≤6 bone metastases on the bone scan). CONCLUSIONS: The data showed that bone-targeted therapy using 1 dose of Sr-89 combined with chemohormonal ablation therapy did not favorably affect the PFS of patients with castrate-sensitive prostate cancer. The combined therapy was feasible and safe. Whether such bone-targeted therapy provides a favorable outcome for those patients with a greater tumor burden in the bone warrants further investigation.

Radium-223 Treatment Produces Prolonged Suppression of Resident Osteoblasts and Decreased Bone Mineral Density in Trabecular Bone in Osteoblast Reporter Mice.

Radium 223 (Ra-223) is an α-emitting bone-homing radiopharmaceutical that targets tumor-induced osteoblasts and is used to reduce bone pain and prolong overall survival in men with bone-metastatic, castrate-resistant prostate cancer. However, increased fracture risk in skeletal sites with no bone metastasis has been observed in patients treated with Ra-223. Both luciferase- or green fluorescence protein (GFP)-labeled osteoblast reporter mice were used to monitor the effect of Ra-223 on resident osteoblasts and normal bone structure. Upon Ra-223 treatment, 70% of resident osteoblasts were reduced within 2 days, and the osteoblast reduction lasted for at least 18 weeks without detectable recovery, as measured by in vivo bioluminescent imaging. In GFP-labeled osteoblast reporter mice, Ra-223 mainly reduced osteoblasts localized in the trabecular bone areas; the osteoblasts in the growth plates were less affected. Micro-computed tomography analyses showed that Ra-223 significantly reduced bone mineral density and bone microstructure in the trabecular area of femurs but not in the cortical bone. Tumor-induced bone was generated by inoculating osteogenic TRAMP-BMP4 prostate cancer cells into the mouse femurs; Ra-223 treatment significantly reduced tumor-induced osteoblasts. Our study shows that Ra-223 affects bone structures that are not involved in bone metastasis. Strategies that improve bone health may reduce fracture risk in patients receiving Ra-223.

Updated 5-year results for short course abiraterone acetate and LHRH agonist for unfavorable intermediate and favorable high-risk prostate cancer.

Combined androgen deprivation therapy (ADT) and radiotherapy (RT) improves outcomes for intermediate and high-risk prostate cancer. Treatment intensification with abiraterone acetate/prednisone (AAP) provides additional benefit for high-risk disease. We previously reported 3-year outcomes of a single-arm prospective multicenter trial (AbiRT trial) of 33 patients with unfavorable intermediate risk (UIR) and favorable high risk (FHR) prostate cancer undergoing short course, combination therapy with ADT, AAP, and RT. Here we report the final analysis demonstrating a high rate of testosterone recovery (97%) and excellent biochemical progression-free survival (97%) at 5 years. These data support comparative prospective studies of shorter, more potent ADT courses in favorable high-risk prostate cancer.

Integrative Molecular Analyses of the MD Anderson Prostate Cancer Patient-derived Xenograft (MDA PCa PDX) Series.

PURPOSE: Develop and deploy a robust discovery platform that encompasses heterogeneity, clinical annotation, and molecular characterization and overcomes the limited availability of prostate cancer models. This initiative builds on the rich MD Anderson (MDA) prostate cancer (PCa) patient-derived xenograft (PDX) resource to complement existing publicly available databases by addressing gaps in clinically annotated models reflecting the heterogeneity of potentially lethal and lethal prostate cancer. EXPERIMENTAL DESIGN: We performed whole-genome, targeted, and RNA sequencing in representative samples of the same tumor from 44 PDXs derived from 38 patients linked to donor tumor metadata and corresponding organoids. The cohort includes models derived from different morphologic groups, disease states, and involved organ sites (including circulating tumor cells), as well as paired samples representing heterogeneity or stages before and after therapy. RESULTS: The cohort recapitulates clinically reported alterations in prostate cancer genes, providing a data resource for clinical and molecular interrogation of suitable experimental models. Paired samples displayed conserved molecular alteration profiles, suggesting the relevance of other regulatory mechanisms (e.g., epigenomic) influenced by the microenvironment and/or treatment. Transcriptomically, models were grouped on the basis of morphologic classification. DNA damage response-associated mechanisms emerged as differentially regulated between adenocarcinoma and neuroendocrine prostate cancer in a cross-interrogation of PDX/patient datasets. CONCLUSIONS: We addressed the gap in clinically relevant prostate cancer models through comprehensive molecular characterization of MDA PCa PDXs, providing a discovery platform that integrates with patient data and benchmarked to therapeutically relevant consensus clinical groupings. This unique resource supports robust hypothesis generation and testing from basic, translational, and clinical perspectives.

A Modular Trial of Androgen Signaling Inhibitor Combinations Testing a Risk-Adapted Strategy in Patients with Metastatic Castration-Resistant Prostate Cancer.

PURPOSE: To determine the efficacy and safety of risk-adapted combinations of androgen signaling inhibitors and inform disease classifiers for metastatic castration-resistant prostate cancers. PATIENTS AND METHODS: In a modular, randomized phase II trial, 192 men were treated with 8 weeks of abiraterone acetate, prednisone, and apalutamide (AAPA; module 1) and then allocated to modules 2 or 3 based on satisfactory (≥50% PSA decline from baseline and <5 circulating tumor cell/7.5 mL) versus unsatisfactory status. Men in the former were randomly assigned to continue AAPA alone (module 2A) or with ipilimumab (module 2B). Men in the latter group had carboplatin + cabazitaxel added to AAPA (module 3). Optional baseline biopsies were subjected to correlative studies. RESULTS: Median overall survival (from allocation) was 46.4 [95% confidence interval (CI), 39.2-68.2], 41.4 (95% CI, 33.3-49.9), and 18.7 (95% CI, 14.3-26.3) months in modules 2A (n = 64), 2B (n = 64), and 3 (n = 59), respectively. Toxicities were within expectations. Of 192 eligible patients, 154 (80.2%) underwent pretreatment metastatic biopsies. The aggressive-variant prostate cancer molecular profile (defects in ≥2 of p53, RB1, and PTEN) was associated with unsatisfactory status. Exploratory analyses suggested that secreted phosphoprotein 1-positive and insulin-like growth factor-binding protein 2-positive macrophages, druggable myeloid cell markers, and germline pathogenic mutations were enriched in the unsatisfactory group. CONCLUSIONS: Adding ipilimumab to AAPA did not improve outcomes in men with androgen-responsive metastatic castration-resistant prostate cancer. Despite the addition of carboplatin + cabazitaxel, men in the unsatisfactory group had shortened survivals. Adaptive designs can enrich for biologically and clinically relevant disease subgroups to contribute to the development of marker-informed, risk-adapted therapy strategies in men with prostate cancer.

Body composition as a determinant of the therapeutic index with androgen signaling inhibition.

BACKGROUND: Androgen signaling is central to prostate cancer and men's health. Prior data indicates that increasing body fat is unfavorable in the localized setting yet associated with favorable outcomes in men with metastatic disease. Understanding the biological links between adiposity and prostate cancer may optimize the therapeutic index with ASI. We hypothesized that host adiposity and androgen synthesis are linked to the efficacy and toxicity of ASI for men with metastatic castration-resistant prostate cancer (mCRPC). METHODS: A post-hoc analysis was done of NCT02703623 where men with mCRPC (n = 186) were treated for 8 weeks with abiraterone acetate, prednisone, and apalutamide (AAPA), and a satisfactory response was defined as a PSA decline >50%. Body composition was measured on baseline CT scans. Germline DNA WES was performed with a focus on variants in steroidogenic genes. Adipokine levels were measured in pre-treatment plasma. RESULTS: Germline polymorphisms in 3 genes involved in androgen synthesis (AKR1C3 rs12529, CYP17A1 rs6162, SRD5A2 rs523349) were associated with differences in body composition at baseline on ADT alone (prior to receipt of AAPA). Elevated subcutaneous adipose tissue index (SATi, p = 0.02), visceral adipose tissue index (VATi, p = 0.03), and BMI (p = 0.04) were associated with satisfactory response to AAPA. Leptin had positive correlation with VATi (r = 0.47) and SATi (r = 0.48). CONCLUSION: Inherited polymorphisms in androgen synthesis correlated with differences in body composition after exposure to ADT and warrant further investigation as candidate markers for body composition toxicity. Elevated subcutaneous and visceral adiposity were associated with improved response to ASI.

Optimal therapy sequencing in metastatic castration-resistant prostate cancer.

Prostate cancer is the most common cancer in men worldwide, accounting for approximately 242,000 new cases and 28,000 deaths annually in the USA. Although localized disease is often curable, advanced disease is generally not, especially when the cancer becomes castration-resistant and metastasizes to bone. Fortunately, advances in research have led to the recent approval of several novel therapies for the treatment of metastatic disease, and many other promising agents are in development. With this success arises the distinct challenge of optimizing both sequencing and the design of rational combinations with these agents. This review focuses on practical and experimental approaches to this challenge.

Tat-binding protein-1, a component of the 26S proteasome, contributes to the E3 ubiquitin ligase function of the von Hippel-Lindau protein.

von Hippel-Lindau (VHL) gene inactivation occurs in von Hippel-Lindau (VHL) disease. The protein pVHL functions in a multi-subunit E3 ubiquitin ligase that targets the hypoxia-inducible transcription factor Hif1 alpha for proteasomal degradation during normoxia. We establish that pVHL binds to Tat-binding protein-1 (TBP-1), a component of the 19S regulatory complex of the proteasome. TBP-1 associates with the beta-domain of pVHL and complexes with pVHL and Hif1 alpha in vivo. Overexpression of TBP-1 promotes degradation of Hif1 alpha in a pVHL-dependent manner that requires the ATPase domain of TBP-1. Blockade of TBP-1 expression by small interfering RNA (siRNA) causes prolonged degradation kinetics of Hif1 alpha. Several distinct mutations in exon 2 of VHL disrupt binding of pVHL to TBP-1. A pVHL mutant containing a P154L substitution coimmunoprecipitates with Hif1 alpha, but not TBP-1, and does not promote degradation of Hif1 alpha. Thus, the ability of pVHL to degrade Hif1 alpha depends in part on its interaction with TBP-1 and suggests a new mechanism for Hif1 alpha stabilization in some pVHL-deficient tumors.

Monitoring Glucocorticoid Receptor in Plasma-derived Extracellular Vesicles as a Marker of Resistance to Androgen Receptor Signaling Inhibition in Prostate Cancer.

Disease progression following androgen ablation was shown to be associated with upregulation of the glucocorticoid receptor (GR). Longitudinal monitoring of GR expression in circulating extracellular vesicles (EV) may reflect changes in the tumor cell and facilitates detection of acquired resistance. We utilized LNCaP, LREX cells and a patient-derived xenograft, MDA PDX 322-2-6a, for in vitro and in vivo experiments. Plasma-derived EVs were isolated from patients with localized high-risk prostate cancer undergoing androgen ablation. The mRNA levels of GR in EVs and their responsive genes were detected by transcriptome analysis, qRT-PCR and the protein levels by Western blot analysis. We detected changes in GR expression at mRNA and protein levels in EVs derived from LNCaP and LREX cells in in vitro studies. In in vivo experiments, LNCaP and the PDX MDA 322-2-6a-bearing mice were treated with enzalutamide. GR levels in plasma-derived EVs were increased only in those tumors that did not respond to enzalutamide. Treatment of mice bearing enzalutamide-resistant tumors with a GR inhibitor in combination with enzalutamide led to a transient pause in tumor growth in a subset of tumors and decreased GR levels intracellular and in plasma-derived EVs. In a subgroup of patients with high-risk localized prostate cancer treated with androgen signaling inhibition, GR was found upregulated in matching tissue and plasma EVs. These analyses showed that GR levels in plasma-derived EVs may be used for monitoring the transition of GR expression allowing for early detection of resistance to androgen ablation treatment. SIGNIFICANCE: Longitudinal monitoring of GR expression in plasma-derived EVs from patients with prostate cancer treated with androgen signaling inhibitors facilitates early detection of acquisition of resistance to androgen receptor signaling inhibition in individual patients.

Prostate cancer-induced endothelial-to-osteoblast transition generates an immunosuppressive bone tumor microenvironment.

Immune checkpoint therapy has limited efficacy for patients with bone metastatic castrate-resistant prostate cancer (bmCRPC). In this study, we revealed a novel mechanism that may account for the relative resistance of bmCRPC to immune checkpoint therapy. We found that prostate cancer (PCa)-induced bone via endothelial-to-osteoblast (EC-to-OSB) transition causes an ingress of M2-like macrophages, leading to an immunosuppressive bone tumor microenvironment (bone-TME). Analysis of a bmCRPC RNA-seq dataset revealed shorter overall survival in patients with an M2-high versus M2-low signature. Immunohistochemical (IHC) analysis showed CD206 + M2-like macrophages were enriched in bmCRPC specimens compared with primary tumors or lymph node metastasis. In osteogenic PCa xenografts, CD206 + macrophages were enriched adjacent to tumor-induced bone. FACS analysis showed an increase in CD206 + cells in osteogenic tumors compared to non-osteogenic tumors. Genetic or pharmacological inhibition of the EC-to-OSB transition reduced aberrant bone and M2-like macrophages in osteogenic tumors. RNAseq analysis of tumor-associated macrophages from osteogenic (bone-TAMs) versus non-osteogenic (ctrl-TAMs) tumors showed high expression of an M2-like gene signature, canonical and non-canonical Wnt pathways, and a decrease in an M1-like gene signature. Isolated bone-TAMs suppressed T-cell proliferation while ctrl-TAMs did not. Mechanistically, EC-OSB hybrid cells produced paracrine factors, including Wnts, CXCL14 and LOX, which induced M2 polarization and recruited M2-like TAMs to bone-TME. Our study thus links the unique EC-to-OSB transition as an "upstream" event that drives "downstream" immunosuppression in the bone-TME. These studies suggest that therapeutic strategies that inhibit PCa-induced EC-to-OSB transition may reverse immunosuppression to promote immunotherapeutic outcomes in bmCRPC. Significance: The insight that prostate cancer-induced bone generates an immunosuppressive bone tumor microenvironment offers a strategy to improve responses to immunotherapy approaches in patients with bone metastatic castrate-resistant prostate cancer.

SPOP Mutations Target STING1 Signaling in Prostate Cancer and Create Therapeutic Vulnerabilities to PARP Inhibitor-Induced Growth Suppression.

PURPOSE: Speckle-type POZ protein (SPOP) is important in DNA damage response (DDR) and maintenance of genomic stability. Somatic heterozygous missense mutations in the SPOP substrate-binding cleft are found in up to 15% of prostate cancers. While mutations in SPOP predict for benefit from androgen receptor signaling inhibition (ARSi) therapy, outcomes for patients with SPOP-mutant (SPOPmut) prostate cancer are heterogeneous and targeted treatments for SPOPmut castrate-resistant prostate cancer (CRPC) are lacking. EXPERIMENTAL DESIGN: Using in silico genomic and transcriptomic tumor data, proteomics analysis, and genetically modified cell line models, we demonstrate mechanistic links between SPOP mutations, STING signaling alterations, and PARP inhibitor vulnerabilities. RESULTS: We demonstrate that SPOP mutations are associated with upregulation of a 29-gene noncanonical (NC) STING (NC-STING) signature in a subset of SPOPmut, treatment-refractory CRPC patients. We show in preclinical CRPC models that SPOP targets and destabilizes STING1 protein, and prostate cancer-associated SPOP mutations result in upregulated NC-STING-NF-κB signaling and macrophage- and tumor microenvironment (TME)-facilitated reprogramming, leading to tumor cell growth. Importantly, we provide in vitro and in vivo mechanism-based evidence that PARP inhibitor (PARPi) treatment results in a shift from immunosuppressive NC-STING-NF-κB signaling to antitumor, canonical cGAS-STING-IFNß signaling in SPOPmut CRPC and results in enhanced tumor growth inhibition. CONCLUSIONS: We provide evidence that SPOP is critical in regulating immunosuppressive versus antitumor activity downstream of DNA damage-induced STING1 activation in prostate cancer. PARPi treatment of SPOPmut CRPC alters this NC-STING signaling toward canonical, antitumor cGAS-STING-IFNß signaling, highlighting a novel biomarker-informed treatment strategy for prostate cancer.

Immune and pathologic responses in patients with localized prostate cancer who received daratumumab (anti-CD38) or edicotinib (CSF-1R inhibitor).

BACKGROUND: The prostate tumor microenvironment (TME) is immunosuppressive, with few effector T cells and enrichment of inhibitory immune populations, leading to limited responses to treatments such as immune checkpoint therapies (ICTs). The immune composition of the prostate TME differs across soft tissue and bone, the most common site of treatment-refractory metastasis. Understanding immunosuppressive mechanisms specific to prostate TMEs will enable rational immunotherapy strategies to generate effective antitumor immune responses. Daratumumab (anti-CD38 antibody) and edicotinib (colony-stimulating factor-1 receptor (CSF-1R) inhibitor) may alter the balance within the prostate TME to promote antitumor immune responses. HYPOTHESIS: Daratumumab or edicotinib will be safe and will alter the immune TME, leading to antitumor responses in localized prostate cancer. PATIENTS AND METHODS: In this presurgical study, patients with localized prostate cancer received 4 weekly doses of daratumumab or 4 weeks of daily edicotinib prior to radical prostatectomy (RP). Treated and untreated control (Gleason score ≥8 in prostate biopsy) prostatectomy specimens and patient-matched pre- and post-treatment peripheral blood mononuclear cells (PBMCs) and bone marrow samples were evaluated. The primary endpoint was incidence of adverse events (AEs). The secondary endpoint was pathologic complete remission (pCR) rate. RESULTS: Twenty-five patients were treated (daratumumab, n=15; edicotinib, n=10). All patients underwent RP without delays. Grade 3 treatment-related AEs with daratumumab occurred in 3 patients (12%), and no ≥grade 3 treatment-related AEs occurred with edicotinib. No changes in serum prostate-specific antigen (PSA) levels or pCRs were observed. Daratumumab led to a decreased frequency of CD38+ T cells, natural killer cells, and myeloid cells in prostate tumors, bone marrow, and PBMCs. There were no consistent changes in CSF-1R+ immune cells in prostate, bone marrow, or PBMCs with edicotinib. Neither treatment induced T cell infiltration into the prostate TME. CONCLUSIONS: Daratumumab and edicotinib treatment was safe and well-tolerated in patients with localized prostate cancer but did not induce pCRs. Decreases in CD38+ immune cells were observed in prostate tumors, bone marrow, and PBMCs with daratumumab, but changes in CSF-1R+ immune cells were not consistently observed with edicotinib. Neither myeloid-targeted agent alone was sufficient to generate antitumor responses in prostate cancer; thus, combinations with agents to induce T cell infiltration (eg, ICTs) will be needed to overcome the immunosuppressive prostate TME.

Addition of Metastasis-Directed Therapy to Intermittent Hormone Therapy for Oligometastatic Prostate Cancer: The EXTEND Phase 2 Randomized Clinical Trial.

Importance: Despite evidence demonstrating an overall survival benefit with up-front hormone therapy in addition to established synergy between hormone therapy and radiation, the addition of metastasis-directed therapy (MDT) to hormone therapy for oligometastatic prostate cancer, to date, has not been evaluated in a randomized clinical trial. Objective: To determine in men with oligometastatic prostate cancer whether the addition of MDT to intermittent hormone therapy improves oncologic outcomes and preserves time with eugonadal testosterone compared with intermittent hormone therapy alone. Design, Setting, Participants: The External Beam Radiation to Eliminate Nominal Metastatic Disease (EXTEND) trial is a phase 2, basket randomized clinical trial for multiple solid tumors testing the addition of MDT to standard-of-care systemic therapy. Men aged 18 years or older with oligometastatic prostate cancer who had 5 or fewer metastases and were treated with hormone therapy for 2 or more months were enrolled to the prostate intermittent hormone therapy basket at multicenter tertiary cancer centers from September 2018 to November 2020. The cutoff date for the primary analysis was January 7, 2022. Interventions: Patients were randomized 1:1 to MDT, consisting of definitive radiation therapy to all sites of disease and intermittent hormone therapy (combined therapy arm; n = 43) or to hormone therapy only (n = 44). A planned break in hormone therapy occurred 6 months after enrollment, after which hormone therapy was withheld until progression. Main Outcomes and Measures: The primary end point was disease progression, defined as death or radiographic, clinical, or biochemical progression. A key predefined secondary end point was eugonadal progression-free survival (PFS), defined as the time from achieving a eugonadal testosterone level (≥150 ng/dL; to convert to nanomoles per liter, multiply by 0.0347) until progression. Exploratory measures included quality of life and systemic immune evaluation using flow cytometry and T-cell receptor sequencing. Results: The study included 87 men (median age, 67 years [IQR, 63-72 years]). Median follow-up was 22.0 months (range, 11.6-39.2 months). Progression-free survival was improved in the combined therapy arm (median not reached) compared with the hormone therapy only arm (median, 15.8 months; 95% CI, 13.6-21.2 months) (hazard ratio, 0.25; 95% CI, 0.12-0.55; P < .001). Eugonadal PFS was also improved with MDT (median not reached) compared with the hormone therapy only (6.1 months; 95% CI, 3.7 months to not estimable) (hazard ratio, 0.32; 95% CI, 0.11-0.91; P = .03). Flow cytometry and T-cell receptor sequencing demonstrated increased markers of T-cell activation, proliferation, and clonal expansion limited to the combined therapy arm. Conclusions and Relevance: In this randomized clinical trial, PFS and eugonadal PFS were significantly improved with combination treatment compared with hormone treatment only in men with oligometastatic prostate cancer. Combination of MDT with intermittent hormone therapy may allow for excellent disease control while facilitating prolonged eugonadal testosterone intervals. Trial Registration: ClinicalTrials.gov Identifier: NCT03599765.

Comparative Effectiveness Analysis of Treatment Strategies for Surgically Resectable Neuroendocrine Carcinoma of the Urinary Tract.

BACKGROUND: Neoadjuvant chemotherapy (neoCTX) has been recommended as the optimal strategy in surgically resectable neuroendocrine carcinoma (NEC) of the urinary tract (NEC-URO). OBJECTIVE: To determine the systemic therapy regimen and timing, which are most active against NEC-URO. DESIGN, SETTING, AND PARTICIPANTS: We used our institutional historical clinical and pathological database to study 203 patients (cT2, 74%; cT3/4a, 22%; and cTx, 4%) with surgically resectable NEC-URO between November 1985 and May 2020. A total of 141 patients received neoCTX and 62 underwent initial radical surgery, 24 of whom received adjuvant CTX (adjCTX). INTERVENTION: Neoadjuvant CTX with etoposide/cisplatin (EP), an alternating doublet of ifosfamide/doxorubicin (IA) and EP, dose-dense methotrexate/vinblastine/doxorubicin/cisplatin (MVAC), gemcitabine/cisplatin (GC), or others. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Overall survival (OS), downstaging rate, and pathological complete response using a multivariable model adjusting for tumor- and patient-related factors. RESULTS AND LIMITATIONS: Downstaging rate was significantly improved with neoCTX versus initial surgery (49.6% vs 14.5%, p < 0.0001), stage cT2N0 versus cT3/4N0 (44% vs 25%, p = 0.01), or presence of carcinoma in situ (47% vs 28%, p = 0.01). Downstaging was greatest with IA/EP (65%) versus EP (39%), MVAC/GC (27%), or others (36%, p = 0.04). After adjusting for age and Eastern Cooperative Oncology Group performance status, IA/EP was still associated with improved downstaging (odds ratio = 3.7 [1.3-10.2], p = 0.01). At a median follow-up of 59.7 mo, 5-yr OS rates for neoCTX followed by surgery, surgery alone, and surgery followed by adjCTX were 57%, 22%, and 30%, respectively. An NEC regimen (IA/EP or EP) versus a urothelial regimen (MVAC/GC or others) was associated with improved survival (145.4 vs 42.5 mo, hazard ratio = 0.49, 95% confidence interval: 0.25-0.94). CONCLUSIONS: Neoadjuvant CTX remains the standard-of-care treatment for NEC-URO with an advantage for NEC regimens over traditional urothelial regimens. IA/EP improves pathological downstaging at the time of surgery compared with EP, but is reserved for younger and higher function patients. PATIENT SUMMARY: In this report, we looked at the outcomes from invasive neuroendocrine carcinoma of the urinary tract in a large US population. We found that the outcomes varied with treatment strategy. We conclude that the best outcomes are seen in patients treated with chemotherapy prior to surgery and regimens tailored to histology and tolerance.

Retinoic Acid Receptor Activation Reduces Metastatic Prostate Cancer Bone Lesions by Blocking the Endothelial-to-Osteoblast Transition.

Metastatic prostate cancer in the bone induces bone-forming lesions that contribute to progression and therapy resistance. Prostate cancer-induced bone formation originates from endothelial cells (EC) that have undergone endothelial-to-osteoblast (EC-to-OSB) transition in response to tumor-secreted BMP4. Current strategies targeting prostate cancer-induced bone formation are lacking. Here, we show that activation of retinoic acid receptor (RAR) inhibits EC-to-OSB transition and reduces prostate cancer-induced bone formation. Treatment with palovarotene, an RARγ agonist being tested for heterotopic ossification in fibrodysplasia ossificans progressiva, inhibited EC-to-OSB transition and osteoblast mineralization in vitro and decreased tumor-induced bone formation and tumor growth in several osteogenic prostate cancer models, and similar effects were observed with the pan-RAR agonist all-trans-retinoic acid (ATRA). Knockdown of RARα, ß, or γ isoforms in ECs blocked BMP4-induced EC-to-OSB transition and osteoblast mineralization, indicating a role for all three isoforms in prostate cancer-induced bone formation. Furthermore, treatment with palovarotene or ATRA reduced plasma Tenascin C, a factor secreted from EC-OSB cells, which may be used to monitor treatment response. Mechanistically, BMP4-activated pSmad1 formed a complex with RAR in the nucleus of ECs to activate EC-to-OSB transition. RAR activation by palovarotene or ATRA caused pSmad1 degradation by recruiting the E3-ubiquitin ligase Smad ubiquitination regulatory factor1 (Smurf1) to the nuclear pSmad1/RARγ complex, thus blocking EC-to-OSB transition. Collectively, these findings suggest that palovarotene can be repurposed to target prostate cancer-induced bone formation to improve clinical outcomes for patients with bone metastasis. SIGNIFICANCE: This study provides mechanistic insights into how RAR agonists suppress prostate cancer-induced bone formation and offers a rationale for developing RAR agonists for prostate cancer bone metastasis therapy. See related commentary by Bhowmick and Bhowmick, p. 2975.