Androgen Receptor Signaling Inhibitors Research Articles

Metastatic Prostate Cancer-A Review of Current Treatment Options and Promising New Approaches.

Androgen deprivation therapy (ADT) alone has been the standard of care for many years in men with metastatic prostate cancer. Due to the limited survival under this monotherapy, many new treatment options have been developed in the last few years. Regarding hormone-sensitive prostate cancer, combination therapies of two or three agents of ADT, androgen receptor signaling inhibitors (ARSI) and chemotherapy have been established and led to a significant benefit in overall survival. Additionally, in patients with metastatic castration-resistant prostate cancer, there are many new therapeutic approaches. Chemotherapy alone has been the standard of care in this situation. In the last years, some new therapeutic options have been developed, which led to an improved survival after progression under chemotherapy. These therapies include ARSI, PARP inhibitors and Lu-PSMA radioligand therapy. The use of a bispecific T-cell engager (BiTE) in this setting is a new promising therapeutic approach, which has not been established as standard of care yet. The role of immunotherapy in prostate cancer is still under investigation. Overall, many new treatment options make prostate cancer therapy a challenging and promising field.

Molecular features and race-associated outcomes of SPOP-mutant metastatic castration-resistant prostate cancer.

Inactivating alterations in SPOP frequently occur in prostate cancer and promote increased dependency on androgen receptor (AR)-mediated oncogenic signaling. The presence of SPOP mutation (SPOP-mutant [SPOP-mut]) may therefore impact therapeutic outcomes with AR-directed therapies and docetaxel in metastatic castration-resistant (mCRPC). This was a retrospective study of mCRPC patients treated at an urban academic hospital (n = 103). Patients underwent tumor DNA sequencing to determine SPOP mutational status (SPOP-mut). Outcomes measured were overall survival (OS) from diagnosis and treatment with second-generation AR signaling inhibitor (ARSI) or docetaxel and time to PSAprogression (prostate-specific antigen-progression-free survival[PSA-PFS]) compared by SPOP status using Kaplan-Meier curves and log-rank test. The univariable and multivariable Cox proportional hazard model evaluated the association of SPOPmutation and outcomes adjusted for clinicopathologic features. SPOP-mut was associated with longer PSA-PFS in mCRPC (median 1.79 vs. 0.84 years; p = 0.06) andmultivariate analysis (hazard ratio [HR] = 0.37;95% confidence interval [CI]: 0.17-0.84;p = 0.02). SPOP-mut demonstrated a higher median PSA decline compared to SPOP wild-type (median decline 100% vs. 92%, p = 0.02). SPOP-mut was not associated with OS from the start of ARSI or docetaxel (median OS not reached vs. 2.0 years)or PSA-PFS on docetaxel (median PSA-PFS 0.4vs. 0.5 years) in mCRPC. The majority of SPOPmutations were identified in African American (AA) patients (69.2%) compared to Caucasian patients (30.8%). Race-associated multivariate analysis revealed no significant differences in OS from the start of ARSI or the start of docetaxeland no differences in ARSI or docetaxel PSA-PFS between AA and Caucasian patients. Molecular profiling demonstrated that AA patients had a higher frequency of SPOPmutations and greater heterogeneity of SPOP variants within the coding sequence. Analysis of concurrent genomic alterations revealed that SPOPmutationsco-occur with APC mutations (p = 0.001) and alterations in the Wnt pathway (p = 0.017). Inactivating mutations in SPOP are associated with better response to ARSI treatment in mCRPC overall. Additional analysis with a larger cohort is needed to evaluate the association of SPOP status and outcomes with docetaxel. Race-associated clinical outcomes and molecular features were observed, suggesting the benefit of biomarker-directed therapy selection for individualized patient subsets in guiding treatment decisions for mCRPC patients.

Novel inhibition of AKR1C3 and androgen receptor axis by PTUPB synergizes enzalutamide treatment in advanced prostate cancer.

Castration-resistant prostate cancer (CRPC) is the main driving force of mortality in prostate cancer patients. Among the parameters contributing to the progression of CRPC and treatment failure, elevation of the steroidogenic enzyme AKR1C3 and androgen receptor variant 7 (AR-V7) are frequently reported. The AKR1C3/AR-V7 complex has been recognized as a major driver for drug resistance in advanced prostate cancer. Herein we report that the level of AKR1C3 is reciprocally regulated by the full-length androgen receptor (AR-FL) through binding to the distal enhancer region of the AKR1C3 gene. A novel function of PTUPB in AKR1C3 inhibition was discovered and PTUPB showed more effectiveness than indomethacin and celecoxib in suppressing AKR1C3 activity and CRPC cell growth. PTUPB synergizes with enzalutamide treatment in tumor suppression and gene signature regulation. Combination treatments with PTUPB and enzalutamide provide benefits by blocking AR/AR-V7 signaling, which inhibits the growth of castration relapsed VCaP xenograft tumors and patient-derived xenograft organoids. Targeting of the ARK1C3/AR/AR-V7 axis with PTUPB and enzalutamide may overcome drug resistance to AR signaling inhibitors in advanced prostate cancer.

Systemic Therapies for Metastatic Castration-Resistant Prostate Cancer: An Updated Review.

The introduction of novel therapeutic agents for advanced prostate cancer has led to a wide range of treatment options for patients with metastatic castration-resistant prostate cancer (mCRPC). In the past decade, new treatment options for mCRPC, including abiraterone, enzalutamide, docetaxel, cabazitaxel, sipuleucel-T, radium-223, 177Lu-PSMA-617, and Olaparib, have demonstrated a survival benefit in phase 3 trials. Bone-modifying agents have become part of the overall treatment strategy for mCRPC, in which denosumab and zoledronic acid reduce skeletal-related events. Recently, androgen receptor-signaling inhibitors (ARSIs) and docetaxel have been used upfront against metastatic castration-sensitive prostate cancer. Further, triplet therapy with ARSI, docetaxel, and androgen deprivation therapy is emerging. However, cross-resistance may occur between these treatments, and the optimal treatment sequence must be considered. The sequential administration of ARSIs, such as abiraterone and enzalutamide, is associated with limited efficacy; however, cabazitaxel is effective for patients with mCRPC who were previously treated with docetaxel and had disease progression during treatment with ARSI. Radioligand therapy with 177Lu-PSMA-617 is a new effective class of therapy for patients with advanced PSMA-positive mCRPC. Tumors with gene alterations that affect homologous recombination repair, such as BRCA1 and BRCA2 alterations, are sensitive to poly (adenosine diphosphate-ribose) polymerase (PARP) inhibitors in mCRPC. This review sought to highlight recent advances in systemic therapy for mCRPC and strategies to support patient selection and treatment sequencing.

M6A-modified circRBM33 promotes prostate cancer progression via PDHA1-mediated mitochondrial respiration regulation and presents a potential target for ARSI therapy.

N6-Methyladenosine (m6A) is the most prevalent RNA modification in various types of RNA, including circular RNAs (circRNAs). Mounting evidence has shown that circRNAs may play critical roles in diverse malignancies. However, the biological relevance of m6A modification of circRNAs in prostate cancer (PCa) remains unclear and needs to be elucidated. Our data showed that circRBM33 was m6A-modified and was more highly expressed in PCa cells than in normal cells/tissues. The in vitro and in vivo experiments showed that downregulation/upregulation of circRBM33 inhibited/promoted tumour growth and invasion, respectively. Decreasing m6A levels rescued the tumour-promoting effect of circRBM33. Additionally, once modified by m6A, circRBM33 interacts with FMR1 by forming a binary complex that sustains the mRNA stability of PDHA1, a downstream target gene. Suppressed/overexpressed circRBM33 lowered/enhanced the ATP production, the acetyl-CoA levels and the NADH/NAD+ ratio. Moreover, depletion of circRBM33 significantly increased the response sensitivity to androgen receptor signalling inhibitor (ARSI) therapy, including enzalutamide and darolutamide, in prostate tumours. Our study suggested that the m6A-mediated circRBM33-FMR1 complex can activate mitochondrial metabolism by stabilizing PDHA1 mRNA, which promotes PCa progression, and can attenuate circRBM33 increased ARSI effectiveness in PCa treatment. This newly discovered circRNA may serve as a potential therapeutic target for PCa.

Clinical outcomes of volume of disease on patients receiving enzalutamide versus abiraterone acetate plus prednisone as first-line therapy for metastatic castration-resistant prostate cancer.

Androgen receptor signaling inhibitors (ARSis) abiraterone acetate (AA) plus prednisone and enzalutamide (Enza), are currently the most administered first-line treatments for metastatic castration-resistant prostate cancer (mCRPC). AA and Enza have shown similar overall survival (OS) benefits and there is no consensus upon the best option for mCRPC first-line treatment. Volume of disease may represent a useful biomarker to predict response to therapy in such patients. In this study, we seek to evaluate the impact of volume of disease on patients treated with first-line AA versus Enza for mCRPC. We retrospectively evaluated a cohort of consecutive patients with mCRPC categorized by volume of disease [high volume (HV) or low volume (LV) per E3805 criteria] at ARSi onset and treatment type (AA or Enza), assessing OS and radiographic progression-free survival (rPFS), from therapy start, as co-primary endpoints. Of the 420 patients selected, 170 (40.5%) had LV and received AA (LV/AA), 76 (18.1%) LV and had Enza (LV/Enza), 124 (29.5%) HV and were given AA (HV/AA), and 50 (11.9%) HV and received Enza (HV/Enza). Among patients with LV, OS was significantly longer when treated with Enza [57.2 months; 95% confidence interval (CI): 52.1-62.2 months] versus AA (51.6 months; 95% CI, 42.6-60.6 months; p = 0.003). Consistently, those with LV receiving Enza showed increased rPFS (40.3 months; 95 CI, 25.0-55.7 months) than those having AA (22.0 months; 95% CI, 18.1-26.0 months; p = 0.004). No significant difference in OS or rPFS was observed in those with HV treated with AA versus Enza (p = 0.51 and p = 0.73, respectively). In multivariate analysis of patients with LV, treatment with Enza was independently associated with better prognosis than AA. Within the intrinsic limitations of a retrospective design and small population, our report suggests that volume of disease could be a useful predictive biomarker for patients starting first-line ARSi for mCRPC.

Genetic Perspectives on Prostate Cancer: Unveiling the Impact on Targeted Radionuclide Therapies

Prostate cancer (PCa) is the 2nd most common malignancy in males and the leading cause of cancer-related deaths among men. In recent years, novel therapies have emerged for metastatic castration-resistant prostate cancer (mCRPC) including immunotherapy, androgen-receptor signaling inhibitors, and radio-nuclide therapies. DNA Damage Repair (DDR) genes are frequently mutated in advance PCa and are useful biomarkers for targeted therapy such as poly-ADP ribose polymerase (PARP) inhibitors. DDR gene defects may affect tissue radio-sensitivity and could serve as biomarkers for therapy with alpha and beta-emitting radionuclides. Preliminary clinical reports suggest a potential trend toward longer survival in DDR+ subjects when treated with α-emitters, however, survival benefit was not significant in patients treated with β-emitting radionuclides. A comprehensive study regarding the impact of DDR genes in prostate cancer patients treated with alpha emitters is vital.

Capsaicin exerts anti-benign prostatic hyperplasia effects via inhibiting androgen receptor signaling pathway

Capsaicin exerts anti-benign prostatic hyperplasia effects via inhibiting androgen receptor signaling pathway

Abstract P008: Native Cell-Free DNA sequence analysis reliably infers epigenetically diverse subtypes of prostate cancer

Abstract Background: With the adoption of potent AR signaling inhibitors, there has been a prominent rise in the frequency of treatment-resistant tumor phenotypes. Highly aggressive transdifferentiated tumors may emerge as AR low or AR null prostate cancers (PCa) with or without neuroendocrine signatures. An accurate determination of these epigenetically diverse phenotypic subtypes has direct clinical implications, including therapy choice. Current approaches for disease subtype determination often require tissue biopsies, limiting due to the high risk of comorbidity. For a temporally evolving cancer, a minimally invasive molecular assay is urgently needed to determine disease subtypes accurately to guide clinical decisions. Methods & Results: Cell-free DNA assay emerging as a nextgen tool for cancer early detection and real-time tumor evolution monitoring tool. Cell-free DNA primarily consists of DNA protected by nucleosomes and DNA binding elements and is shed into the bloodstream by cells that undergo apoptosis. We hypothesized that a nucleosome protection map and transcriptional regulation could be reliably determined from circulating tumor DNA (ctDNA) analysis. This analysis can accurately classify advanced prostate cancer into epigenetically divergent subclasses such as adenocarcinoma (ARPC) and neuroendocrine (NEPC). For developing robust phenotype-specific signatures, we performed whole-genome sequencing on plasma cfDNA from 30 PDX lines to achieve moderately deep coverage (>10X) of “pure” human ctDNA sequence data. We applied an analysis framework “Griffin” to determine transcription factor binding sites and transcription start site nucleosome protection signatures, predictive of specific transcription factor activity. We also generated H3K27ac, H3K27me1, and H3K27me3 histone profiles from resected PDX tumors and observed that ctDNA fragmentation and coverage patterns are consistent with histone modifications. Guided by differential nucleosome profiles, we derived a novel ctDNA fragment size variability signature that accurately predicted expression deregulation for phenotype-defining genes. These signatures helped us build an unsupervised statistical model that accurately classified PCa subtypes. We applied our model to 2 clinical cohorts and attained 96% accuracy for classifying patients with well-defined subtypes of advanced PCa, using low coverage sequencing. Conclusion: We have developed a ctDNA analysis method that can accurately classify epigenetically diverse subtypes of advanced prostate cancer, spanning AR active and neuroendocrine subtypes. This scalable and cost-effective approach is also suitable for longitudinal monitoring and prediction of treatment-emergent prostate cancer resulting from therapeutic resistance. Citation Format: Navonil De Sarkar. Native Cell-Free DNA sequence analysis reliably infers epigenetically diverse subtypes of prostate cancer. [abstract]. In: Proceedings of the AACR Special Conference: Precision Prevention, Early Detection, and Interception of Cancer; 2022 Nov 17-19; Austin, TX. Philadelphia (PA): AACR; Can Prev Res 2023;16(1 Suppl): Abstract nr P008.

How the Analysis of the Pathogenetic Variants of DDR Genes Will Change the Management of Prostate Cancer Patients.

Herein, we analyze answers achieved, open questions, and future perspectives regarding the analysis of the pathogenetic variants (PV) of DNA damage response (and repair) (DDR) genes in prostate cancer (PC) patients. The incidence of PVs in homologous recombination repair (HRR) genes among men with metastatic PC varied between 11% and 33%, which was significantly higher than that in non-metastatic PC, and BRCA2 mutations were more frequent when compared to other DDR genes. The determination of the somatic or germline PVs of BRCA2 was able to define a tailored therapy using PARP inhibitors in metastatic castration-resistant prostate cancer (mCRPC) progression after first-line therapy, with significant improvements in the radiologic progression-free survival (rPFS) and overall survival (OS) rates. We propose testing all metastatic PC patients for somatic and germline HRR mutations. Somatic determination on the primary site or on historic paraffin preparations with a temporal distance of no longer than 5 years should be preferred over metastatic site biopsies. The prognostic use of DDR PVs will also be used in selected high-risk cases with non-metastatic stages to better arrange controls and therapeutic primary options. We anticipate that the use of poly-ADP-ribose polymerase (PARP) inhibitors in hormone-sensitive prostate cancer (HSPC) and in combination with androgen receptor signaling inhibitors (ARSI) will be new strategies.

Comparative Proteomic and Transcriptomic Analysis of the Impact of Androgen Stimulation and Darolutamide Inhibition.

Several inhibitors of androgen receptor (AR) function are approved for prostate cancer treatment, and their impact on gene transcription has been described. However, the ensuing effects at the protein level are far less well understood. We focused on the AR signaling inhibitor darolutamide and confirmed its strong AR binding and antagonistic activity using the high throughput cellular thermal shift assay (CETSA HT). Then, we generated comprehensive, quantitative proteomic data from the androgen-sensitive prostate cancer cell line VCaP and compared them to transcriptomic data. Following treatment with the synthetic androgen R1881 and darolutamide, global mass spectrometry-based proteomics and label-free quantification were performed. We found a generally good agreement between proteomic and transcriptomic data upon androgen stimulation and darolutamide inhibition. Similar effects were found both for the detected expressed genes and their protein products as well as for the corresponding biological programs. However, in a few instances there was a discrepancy in the magnitude of changes induced on gene expression levels compared to the corresponding protein levels, indicating post-transcriptional regulation of protein abundance. Chromatin immunoprecipitation DNA sequencing (ChIP-seq) and Hi-C chromatin immunoprecipitation (HiChIP) revealed the presence of androgen-activated AR-binding regions and long-distance AR-mediated loops at these genes.

Suppression of androgen receptor signaling induces prostate cancer migration via activation of the CCL20-CCR6 axis.

The suppression of androgen receptor (AR) expression exacerbates the migration potential of prostate cancer. This study identified a previously unrecognized regulation of the AR-controlled pathway that promotes migration potential in prostate cancer cells. Prostate cancer cells that pass through a transwell membrane (mig cells) have a higher migration potential with a decreased AR expression than parental cells. In this study, we aimed to elucidate the mechanism of migration enhancement associated with the suppression of AR signaling. Expression of C-C motif ligand 20 (CCL20) is upregulated in mig cells, unlike in the parental cells. Knockdown of AR with small interfering RNA (siAR) in LNCaP and C4-2B cells increased CCL20 secretion and enhanced the migration of cancer cells. Mig cells, CCL20-treated cells, and siAR cells promoted cell migration with an enhancement of AKT phosphorylation and Snail expression, while the addition of a C-C chemokine receptor 6 (CCR6, the specific receptor of CCL20) inhibitor, anti-CCL20 antibody, and AKT inhibitor suppressed the activation of AKT and Snail. With 59 samples of prostate cancer tissue, CCL20 secretion was profuse in metastatic cases despite low AR expression levels. Snail expression was associated with the expression of CCL20 and CCR6. A xenograft study showed that the anti-CCL20 antibody significantly inhibited Snail expression, thereby suggesting a new therapeutic approach for castration-resistant prostate cancer with the inhibition of the axis between CCL20 and CCR6.

Androgen Receptor Signaling Inhibition in Advanced Castration Resistance Prostate Cancer: What Is Expected for the Near Future?

The androgen signaling pathway is the cornerstone in the treatment of high risk or advanced prostate cancer patients. However, in recent years, different mechanisms of resistance have been defined in this field, limiting the efficacy of the currently approved antiandrogen drugs. Different therapeutic approaches are under research to assess the role of combination therapies against escape signaling pathways or the development of novel antiandrogen drugs to try to solve the primary or acquired resistance against androgen dependent or independent pathways. The present review aims to summarize the current state of androgen inhibition in the therapeutic algorithm of patients with advanced prostate cancer and the mechanisms of resistance to those available drugs. In addition, this review conducted a comprehensive overview of the main present and future research approaches in the field of androgen receptor inhibition to overcome these resistances and the potential new drugs under research coming into this setting.

Acetyl-CoA Counteracts the Inhibitory Effect of Antiandrogens on Androgen Receptor Signaling in Prostate Cancer Cells.

The commonly used therapeutic management of PC involves androgen deprivation therapy (ADT) followed by treatment with AR signaling inhibitors (ARSI). However, nearly all patients develop drug-resistant disease, with a median progression-free survival of less than 2 years in chemotherapy-naïve men. Acetyl-coenzyme A (acetyl-CoA) is a central metabolic signaling molecule with key roles in biosynthetic processes and cancer signaling. In signaling, acetyl-CoA serves as the acetyl donor for acetylation, a critical post-translational modification. Acetylation affects the androgen receptor (AR) both directly and indirectly increasing expression of AR dependent genes. Our studies reveal that PC cells respond to the treatment with ARSI by increasing expression of ATP-citrate lyase (ACLY), a major enzyme responsible for cytosolic acetyl-CoA synthesis, and up-regulation of acetyl-CoA intracellular levels. Inhibition of ACLY results in a significant suppression of ligand-dependent and -independent routes of AR activation. Accordingly, the addition of exogenous acetyl-CoA, or its precursor acetate, augments AR transcriptional activity and diminishes the anti-AR activity of ARSI. Taken together, our findings suggest that PC cells respond to antiandrogens by increasing activity of the acetyl-coA pathway in order to reinstate AR signaling.

Ginsenoside compound K suppresses tumour growth in the 22Rv1 xenograft model and inhibits androgenic responses via the transcriptional mechanism in human prostate cancer cells.

Androgen receptor (AR) signalling is known to be dispensable for the biology of castration-resistant prostate cancer (CRPC), whereas the AR itself and the residual androgens after castration are crucial for the growth and progression of CRPC. Therefore, there is high demand for novel therapeutic candidates targeting AR itself or aberrant AR signalling to suppress the progression to or the growth of CPRC. Here, we report that ginsenoside compound K (GCK), the primary bioactive metabolite biotransformed from protopanaxadiol (PPD) ginsenoside, acts as a novel AR signalling inhibitor by transcriptionally suppressing AR expression and tumour growth in athymic nude mice. GCK inhibited cell growth in LNCaP, PC-3 and 22Rv1 prostate cancer cell lines and suppressed the expression levels of cell cycle regulators. GCK down-regulated epithelial-mesenchymal transition markers such as vimentin and matrix metalloproteinase 9 (MMP9), whereas E-cadherin was significantly increased in GCK-stimulated LNCaP and 22Rv1 cells. Moreover, GCK treatment markedly decreased both AR and AR-V7 protein levels in LNCaP and 22Rv1 cells, possibly by decreasing AR promoter activity. Experiments with AR promoter-deleted constructs revealed that the region between -412 and -227 is critical for GCK regulation. GCK treatment in athymic nude mice implanted with 22Rv1 CRPC cell lines significantly suppressed tumour growth and AR expression levels in tumour tissues. Collectively, our results suggest that GCK, as a novel AR inhibitor, could be a potential therapeutic agent against prostate cancer and an effective chemopreventive agent to delay the progression to CRPC.

A clinical-grade liquid biomarker detects neuroendocrine differentiation in prostate cancer.

BackgroundNeuroendocrine prostate cancer (NEPC) is an aggressive subtype, the presence of which changes the prognosis and management of metastatic prostate cancer.MethodsWe performed analytical validation of a Circulating Tumor Cell (CTC) multiplex RNA qPCR assay to identify the limit of quantification (LOQ) in cell lines, synthetic cDNA, and patient samples. We next profiled 116 longitudinal samples from a prospectively collected institutional cohort of 17 patients with metastatic prostate cancer (7 NEPC, 10 adenocarcinoma) as well as 265 samples from 139 patients enrolled in 3 adenocarcinoma phase II trials of androgen receptor signaling inhibitors (ARSIs). We assessed a NEPC liquid biomarker via the presence of neuroendocrine markers and the absence of androgen receptor (AR) target genes.ResultsUsing the analytical validation LOQ, liquid biomarker NEPC detection in the longitudinal cohort had a per-sample sensitivity of 51.35% and a specificity of 91.14%. However, when we incorporated the serial information from multiple liquid biopsies per patient, a unique aspect of this study, the per-patient predictions were 100% accurate, with a receiver-operating-curve (ROC) AUC of 1. In the adenocarcinoma ARSI trials, the presence of neuroendocrine markers, even while AR target gene expression was retained, was a strong negative prognostic factor.ConclusionOur analytically validated CTC biomarker can detect NEPC with high diagnostic accuracy when leveraging serial samples that are only feasible using liquid biopsies. Patients with expression of NE genes while retaining AR-target gene expression may indicate the transition to neuroendocrine differentiation, with clinical characteristics consistent with this phenotype.FundingNIH (DP2 OD030734, 1UH2CA260389, R01CA247479, and P30 CA014520), Department of Defense (PC190039 and PC200334), and Prostate Cancer Foundation (Movember Foundation - PCF Challenge Award).

Association between age and efficacy of combination systemic therapies in patients with metastatic hormone-sensitive prostate cancer: a systematic review and meta-analysis.

Combination systemic therapies have become the standard for metastatic hormone-sensitive prostate cancer (mHSPC). However, the effect of age on oncologic outcomes remains unknown. Our aim was to perform a systematic review, meta-analysis, and network meta-analysis (NMA) on the effect of chronological age on overall survival (OS) in patients treated with combination therapies for mHSPC. We searched the PubMed®, Web of ScienceTM, and Scopus® databases to identify randomized controlled trials (RCTs) that analyzed the efficacy of combination systemic therapies using ADT plus docetaxel and/or androgen receptor signaling inhibitor (ARSI) in patients with mHSPC. We included studies, which provided separate hazard ratios (HRs) for younger vs. older patients. The selected age cut-off was 70 years (±5 years). Our outcome of interest was OS. We included nine RCTs with a total of 9183 patients. Younger and older men constituted 51% and 49% of included patients, respectively. Docetaxel plus ADT significantly improved OS among both older (HR 0.79, 95% CI 0.63-0.99, p = 0.04) and younger patients (HR 0.79, 95% CI 0.69-0.90, p < 0.001) with no differences according to age. ARSI plus ADT improved OS in older (HR 0.72, 95% CI 0.64-0.80, p < 0.001) and younger (HR 0.58, 95% CI 0.51-0.66, p < 0.001) patients; younger patients did benefit more (p = 0.02). On NMA treatment ranking, triplet therapy showed the highest probability of OS benefit irrespective of age group; in older patients, the benefit of triplet therapy compared to doublet was less expressed. Patients with mHSPC benefit from combination systemic therapies irrespective of age; the effect is, however, more evident in younger patients. Chronological age alone seems not to be a selection criteria for the administration of combination systemic therapies.

A COP1-GATA2 axis suppresses AR signaling and prostate cancer

Androgen receptor (AR) signaling is crucial for driving prostate cancer (PCa), the most diagnosed and the second leading cause of death in male patients with cancer in the United States. Androgen deprivation therapy is initially effective in most instances of AR-positive advanced or metastatic PCa. However, patients inevitably develop lethal castration-resistant PCa (CRPC), which is also resistant to the next-generation AR signaling inhibitors. Most CRPCs maintain AR expression, and blocking AR signaling remains a main therapeutic approach. GATA2 is a pioneer transcription factor emerging as a key therapeutic target for PCa because it promotes AR expression and activation. While directly inhibiting GATA2 transcriptional activity remains challenging, enhancing GATA2 degradation is a plausible therapeutic strategy. How GATA2 protein stability is regulated in PCa remains unknown. Here, we show that constitutive photomorphogenesis protein 1 (COP1), an E3 ubiquitin ligase, drives GATA2 ubiquitination at K419/K424 for degradation. GATA2 lacks a conserved [D/E](x)xxVP[D/E] degron but uses alternate BR1/BR2 motifs to bind COP1. By promoting GATA2 degradation, COP1 inhibits AR expression and activation and represses PCa cell and xenograft growth and castration resistance. Accordingly, GATA2 overexpression or COP1 mutations that disrupt COP1-GATA2 binding block COP1 tumor-suppressing activities. We conclude that GATA2 is a major COP1 substrate in PCa and that COP1 promotion of GATA2 degradation is a direct mechanism for regulating AR expression and activation, PCa growth, and castration resistance.

Adverse events associated with androgen receptor signaling inhibitors in the treatment of prostate cancer: A systematic review and network meta-analysis.

317 Background: Androgen receptor signaling inhibitors (ARSi) are emerging as standard treatments for prostate cancer across the disease spectrum. With multiple available agents approved, comparing adverse effects between different therapies may guide clinical decision-making. The purpose of this meta-analysis was to compare adverse events (AE) and serious adverse events (sAE) between the ARSi drugs abiraterone, apalutamide, darolutamide, and enzalutamide. Methods: PubMed, Web of Science, Embase, and Clinicaltrials.gov were searched for double-blind, randomized controlled trials for ARSi therapy in the treatment of prostate cancer (both metastatic and non-metastatic settings). Two independent teams extracted AE and sAE data. Studies were synthesized using R with the “Netmeta” package. Results: Thirteen double-blinded, randomized trials of abiraterone, apalutamide, darolutamide or enzalutamide were included in this study. The relative risk ratio (RR) of the most common any-grade AE compared to placebo was highest in enzalutamide with a RR of 1.30 (95% confidence interval [CI], 1.13-1.50), followed by apalutamide (1.20, [0.95-1.53]), abiraterone (1.19, [0.98-1.44]), and darolutamide (1.17, [0.83-1.65]). The risk of any sAE was highest in darolutamide (1.80, [0.91-3.57]), followed by apalutamide (1.75, [1.07-2.87]), abiraterone (1.56, [1.08-2.25]), and enzalutamide (1.57, [1.18-2.09]). For overall ARSi analysis, special sAE of interest included acute coronary syndrome, arrhythmia, and seizure, for which ARSi therapy was associated with an odds ratio (OR) of 2.85 (1.65-4.91), 1.75 (1.25-2.44), and 1.31 (0.57-3.00) respectively. Amongst themselves, enzalutamide had the highest risk of cardiovascular AE compared to non-enzalutamide ARSi (RR = 1.77, [1.42-2.20], p &lt; 0.05). Abiraterone had the lowest risk of musculoskeletal AEs compared to non-abiraterone ARSi (0.79, [0.70-0.88], p &lt; 0.05). No significant differences existed in the other domains of interest. Conclusions: ARSi therapy was associated with a higher risk of AE and sAE in various domains compared to placebo. Our findings suggest that the side-effect profiles of ARSis do not significantly differ except in the case of increased cardiovascular risk with enzalutamide and decreased musculoskeletal risk with abiraterone. This data may aid clinicians in determining personalized therapeutic options for their patents based on side effect profiles.

296 (PB076) - Cellular hormone metabolism is critical for canonical androgen receptor antagonist activity

Background: Second-generation androgen receptor (AR) antagonists and an androgen synthesizing enzyme inhibitor have become the standard of care for advanced prostate cancer (PCa). Clinically-approved AR antagonists bind to the AR ligand binding domain (LBD) and competitively inhibit AR function. Dual action AR inhibitors (DAARIs), which bind to the N-terminal domain (NTD) of the AR inhibit AR signaling and lead AR protein degradation, have been identified by our group as potential therapeutics for PCa.