Development Of Castration-resistant Prostate Cancer Research Articles

Comparative Transcriptomes of Canine and Human Prostate Cancers Identify Mediators of Castration Resistance.

Prostate cancer continues to be one of the most lethal cancers in men. While androgen deprivation therapy is initially effective in treating prostate cancer, most cases of advanced prostate cancer eventually progress to castration-resistant prostate cancer (CRPC), which is incurable. Similarly, the most aggressive form of prostatic carcinoma occurs in dogs that have been castrated. To identify molecular similarities between canine prostate cancer and human CRPC, we performed a comparative analysis of gene expression profiles. Through this transcriptomic analysis, we found that prostatic carcinoma in castrated dogs demonstrates an androgen-indifferent phenotype, characterised by low-androgen receptor and neuroendocrine-associated genes. Notably, we identified two genes, ISG15 and AZGP1, that were consistently up- and down-regulated, respectively, in both canine prostatic carcinoma and human CRPC. Additionally, we identified several other genes, including GPX3, S100P and IFITM1, that exhibited similar expression patterns in both species. Protein-protein interaction network analysis demonstrated that these five genes were part of a larger network of interferon-induced genes, suggesting that they may act together in signalling pathways that are disrupted in prostate cancer. Accordingly, our findings suggest that the interferon pathway may play a role in the development and progression of CRPC in both dogs and humans and chart a new therapeutic approach.

Clinico-Pathological Factors and AR-LBD Mutations in Early and Late Castration-Resistant Prostate Cancer.

Prostate cancer (PCa) is not well understood because of its enormous biological heterogeneity and unreliable progression. We conducted this retrospective analysis to examine the variables predicting early and late progression to castration-resistant PCa (CRPC) for better management of this disease. This single institutional retrospective study was conducted from January 2018 to January 2022. A total of 98 consecutive men meeting with the diagnosis of CRPC as per the inclusion criteria were included in the study and were stratified in four quartiles on the basis of time to CRPC (time to castration resistance [TTCR]) development. Early CRPC (1st quartile, TTCR = 6-12 months) and late CRPC (4th quartile, TTCR = 38-120 months) were then compared on the basis of different clinical, pathological and AR-LBD sequence to find the correlation with response duration. Median time to develop castration resistance was 25 ± 26.44 months. The mean age of the patients was 66.8 ± 9.20 years and median baseline PSA was calculated 100±685.06 ng/mL respectively. Higher Gleason score (≥7-10) was found to be significantly associated with early development of CRPC (p<0.001) and lower nadir PSA was significantly indicating late CRPC progression (p<0.005). No mutations were found in androgen receptor exon-5, 6, 7 except a homozygous mutation in the 7th intronic region, which is involved in splice variants formation playing noteworthy role in CRPC development. Time for metastatic PCa to CRPC ranges from 6-120 months revealing its heterogeneous nature. Early age presentation in the clinic and high initial PSA and high grade (GS>7) at diagnosis were positively associated with early CRPC while lower nadir PSA was correlated with late CRPC progression. No remarkable genomic mutations were discovered. Therefore, more data are needed and further research is required with large no. of patients to discover the predictive prognostic biomarkers for better patients' management.

Treatment-induced stemness and lineage plasticity in driving prostate cancer therapy resistance.

Most human cancers are heterogeneous consisting of cancer cells at different epigenetic and transcriptional states and with distinct phenotypes, functions, and drug sensitivities. This inherent cancer cell heterogeneity contributes to tumor resistance to clinical treatment, especially the molecularly targeted therapies such as tyrosine kinase inhibitors (TKIs) and androgen receptor signaling inhibitors (ARSIs). Therapeutic interventions, in turn, induce lineage plasticity (also called lineage infidelity) in cancer cells that also drives therapy resistance. In this Perspective, we focus our discussions on cancer cell lineage plasticity manifested as treatment-induced switching of epithelial cancer cells to basal/stem-like, mesenchymal, and neural lineages. We employ prostate cancer (PCa) as the prime example to highlight ARSI-induced lineage plasticity during and towards development of castration-resistant PCa (CRPC). We further discuss how the tumor microenvironment (TME) influences therapy-induced lineage plasticity. Finally, we offer an updated summary on the regulators and mechanisms driving cancer cell lineage infidelity, which should be therapeutically targeted to extend the therapeutic window and improve patients' survival.

Comparative Transcriptomes of Canine and Human Prostate Cancers Identify Mediators of Castration Resistance.

Prostate cancer continues to be one of the most lethal cancers in men. While androgen-deprivation therapy is initially effective in treating prostate cancer, most cases of advanced prostate cancer eventually progress to castration-resistant prostate cancer (CRPC), which is incurable. Similarly, the most aggressive form of prostatic carcinoma occurs in dogs that have been castrated. To identify molecular similarities between canine prostate cancer and human CRPC, we performed a comparative analysis of gene expression profiles. Through this transcriptomic analysis, we found that prostatic carcinoma in castrated dogs demonstrate an androgen indifferent phenotype, characterized by low androgen receptor and neuroendocrine associated genes. Notably, we identified two genes, ISG15 and AZGP1 that were consistently up- and downregulated, respectively, in both canine prostatic carcinoma and human CRPC. Additionally, we identified several other genes, including GPX3, S100P, and IFITM1, that exhibited similar expression patterns in both species. Protein-protein interaction network analysis demonstrated that these 5 genes were part of a larger network of interferon-induced genes, suggesting that they may act together in signaling pathways that are disrupted in prostate cancer. Accordingly, our findings suggest that the interferon pathway may play a role in the development and progression of CRPC in both dogs and humans and chart a new therapeutic approach.

GATA2 promotes castration-resistant prostate cancer development by suppressing IFN-β axis-mediated antitumor immunity.

Castration-resistant prostate cancer (CRPC) nearly inevitably develops after long-term treatment with androgen deprivation therapy (ADT), leading to significant mortality. Investigating the mechanisms driving CRPC development is imperative. Here, we determined that the pioneer transcription factor GATA2, which is frequently amplified in CRPC patients, inhibits interferon (IFN)-β-mediated antitumor immunity, thereby promoting CRPC progression. Employing a genetically engineered mouse model (GEMM), we demonstrated that GATA2 overexpression hindered castration-induced cell apoptosis and tumor shrinkage, facilitating tumor metastasis and CRPC development. Notably, GATA2 drives castration resistance predominantly via repressing castration-induced activation of IFN-β signaling and CD8+ T-cell infiltration. This finding aligns with the negative correlation between GATA2 expression and IFNB1 expression, as well as CD8+ T-cell infiltration in CRPC patients. Mechanistically, GATA2 recruited PIAS1 as corepressor, and reprogramed the cistrome of IRF3, a key transcription factor of the IFN-β axis, in an androgen-independent manner. Furthermore, we identified a novel silencer element that facilitated the function of GATA2 and PIAS1 through looping to the IFNB1 promoter. Importantly, depletion of GATA2 augmented antitumor immunity and attenuated CRPC development. Consequently, our findings elucidate a novel mechanism wherein GATA2 promotes CRPC progression by suppressing IFN-β axis-mediated antitumor immunity, underscoring GATA2 as a promising therapeutic target for CRPC.

Molecular landscape for risk prediction and personalized therapeutics of castration-resistant prostate cancer: at a glance.

Prostate cancer (PCa) is commonly occurred with high incidence in men worldwide, and many patients will be eventually suffered from the dilemma of castration-resistance with the time of disease progression. Castration-resistant PCa (CRPC) is an advanced subtype of PCa with heterogeneous carcinogenesis, resulting in poor prognosis and difficulties in therapy. Currently, disorders in androgen receptor (AR)-related signaling are widely acknowledged as the leading cause of CRPC development, and some non-AR-based strategies are also proposed for CRPC clinical analyses. The initiation of CRPC is a consequence of abnormal interaction and regulation among molecules and pathways at multi-biological levels. In this study, CRPC-associated genes, RNAs, proteins, and metabolites were manually collected and integrated by a comprehensive literature review, and they were functionally classified and compared based on the role during CRPC evolution, i.e., drivers, suppressors, and biomarkers, etc. Finally, translational perspectives for data-driven and artificial intelligence-powered CRPC systems biology analysis were discussed to highlight the significance of novel molecule-based approaches for CRPC precision medicine and holistic healthcare.

Thio-2 Inhibits Key Signaling Pathways Required for the Development and Progression of Castration-resistant Prostate Cancer.

Therapies that abrogate persistent androgen receptor (AR) signaling in castration-resistant prostate cancer (CRPC) remain an unmet clinical need. The N-terminal domain of the AR that drives transcriptional activity in CRPC remains a challenging therapeutic target. Herein we demonstrate that BCL-2-associated athanogene-1 (BAG-1) mRNA is highly expressed and associates with signaling pathways, including AR signaling, that are implicated in the development and progression of CRPC. In addition, interrogation of geometric and physiochemical properties of the BAG domain of BAG-1 isoforms identifies it to be a tractable but challenging drug target. Furthermore, through BAG-1 isoform mouse knockout studies, we confirm that BAG-1 isoforms regulate hormone physiology and that therapies targeting the BAG domain will be associated with limited "on-target" toxicity. Importantly, the postulated inhibitor of BAG-1 isoforms, Thio-2, suppressed AR signaling and other important pathways implicated in the development and progression of CRPC to reduce the growth of treatment-resistant prostate cancer cell lines and patient-derived models. However, the mechanism by which Thio-2 elicits the observed phenotype needs further elucidation as the genomic abrogation of BAG-1 isoforms was unable to recapitulate the Thio-2-mediated phenotype. Overall, these data support the interrogation of related compounds with improved drug-like properties as a novel therapeutic approach in CRPC, and further highlight the clinical potential of treatments that block persistent AR signaling which are currently undergoing clinical evaluation in CRPC.

Agent-based modeling of the prostate tumor microenvironment uncovers spatial tumor growth constraints and immunomodulatory properties

Inhibiting androgen receptor (AR) signaling through androgen deprivation therapy (ADT) reduces prostate cancer (PCa) growth in virtually all patients, but response may be temporary, in which case resistance develops, ultimately leading to lethal castration-resistant prostate cancer (CRPC). The tumor microenvironment (TME) plays an important role in the development and progression of PCa. In addition to tumor cells, TME-resident macrophages and fibroblasts express AR and are therefore also affected by ADT. However, the interplay of different TME cell types in the development of CRPC remains largely unexplored. To understand the complex stochastic nature of cell-cell interactions, we created a PCa-specific agent-based model (PCABM) based on in vitro cell proliferation data. PCa cells, fibroblasts, “pro-inflammatory” M1-like and “pro-tumor” M2-like polarized macrophages are modeled as agents from a simple set of validated base assumptions. PCABM allows us to simulate the effect of ADT on the interplay between various prostate TME cell types. The resulting in vitro growth patterns mimic human PCa. Our PCABM can effectively model hormonal perturbations by ADT, in which PCABM suggests that CRPC arises in clusters of resistant cells, as is observed in multifocal PCa. In addition, fibroblasts compete for cellular space in the TME while simultaneously creating niches for tumor cells to proliferate in. Finally, PCABM predicts that ADT has immunomodulatory effects on macrophages that may enhance tumor survival. Taken together, these results suggest that AR plays a critical role in the cellular interplay and stochastic interactions in the TME that influence tumor cell behavior and CRPC development.

Glycolysis related lncRNA SNHG3 / miR-139-5p / PKM2 axis promotes castration-resistant prostate cancer (CRPC) development and enzalutamide resistance

Although androgen deprivation therapy (ADT) by the anti-androgen drug enzalutamide (Enz) may improve the survival level of patients with castration-resistant prostate cancer (CRPC), most patients may eventually fail due to the acquired resistance. The reprogramming of glucose metabolism is one type of the paramount hallmarks of cancers. PKM2 (Pyruvate kinase isozyme typeM2) is a speed-limiting enzyme in the glycolytic mechanism, and has high expression in a variety of cancers. Emerging evidence has unveiled that microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) have impact on tumor development and therapeutic efficacy by regulating PKM2 expression. Herein, we found that lncRNA SNHG3, a highly expressed lncRNA in CRPC via bioinformatics analysis, promoted the invasive ability and the Enz resistance of the PCa cells. KEGG pathway enrichment analysis indicated that glucose metabolic process was tightly correlated with lncRNA SNHG3 level, suggesting lncRNA SNHG3 may affect glucose metabolism. Indeed, glucose uptake and lactate content determinations confirmed that lncRNA SNHG3 promoted the process of glycolysis. Mechanistic dissection demonstrated that lncRNA SNHG3 facilitated the advance of CRPC by adjusting the expression of PKM2. Further explorations unraveled the role of lncRNA SNHG3 as a ‘sponge’ of miR-139-5p and released its binding with PKM2 mRNA, leading to PKM2 up-regulation. Together, Our studies suggest that lncRNA SNHG3 / miR-139-5p / PKM2 pathway promotes the development of CRPC via regulating glycolysis process and provides valuable insight into a novel therapeutic approach for the disordered disease.

Identification of PRDX5 as A Target for The Treatment of Castration-Resistant Prostate Cancer.

Treatment of castration-resistant prostate cancer (CRPC) is a long-standing clinical challenge. Traditionally, CRPC drugs work by either reducing dihydrotestosterone biosynthesis or blocking androgen receptor (AR) signaling. Here it is demonstrated that AR inhibitor treatment gives rise to a drug-tolerant persister (DTP) state. The thioredoxin/peroxiredoxin pathway is up-regulated in DTP cells. Peroxiredoxin 5 (PRDX5) promotes AR inhibitor resistance and CRPC development. Inhibition of PRDX5 suppresses DTP cell proliferation in culture, dampens CRPC development in animal models, and stabilizes PSA progression and metastatic lesions in patients. Therefore, the study provides a novel mechanism and potential target for the management of castration-resistant prostate cancer.

JNK promotes the progression of castration-resistant prostate cancer.

Prostate cancer is one of the most common cancers in men worldwide. This study aims to elucidate the roles of c-Jun N-terminal kinase (JNK) in the progression of castration-resistant prostate cancer (CRPC). JNK overexpressing and knockdown cell lines were established on the PC-3 prostate cell line. qPCR and Western blotting were performed to determine the mRNA and protein levels of target genes in prostate tissues and cell lines. MTT and Matrigel invasion assays were conducted to evaluate the cell viability and invasive ability, respectively. The Kaplan-Meier estimator was performed to estimate the overall survival rate and second progression-free survival rate. Pearson's correlation coefficient was used to evaluate the relationship between JNK and prostate-specific antigen (PSA). Relative JNK expression was correlated with Gleason score and PSA value in patients with CRPC. Kaplan-Meier analysis revealed that patients with low JNK expression exhibited high overall survival and second progression-free survival rate. In vitro assays demonstrated that JNK overexpression promoted cell viability and invasion as well as the protein expressions of extracellular signal-regulated kinase (ERK) and matrix metalloproteinase 1 (MMP1) in PC-3 cell lines. JNK overexpression promotes the development of CRPC via the regulation of ERK and MMP1.

Newly developed preclinical models reveal broad-spectrum CDK inhibitors as potent drugs for CRPC exhibiting primary resistance to enzalutamide.

Androgen-deprivation therapy is a standard treatment for advanced prostate cancer. However, most patients eventually acquire resistance and progress to castration-resistant prostate cancer (CRPC). In this study, we established new CRPC cell lines, AILNCaP14 and AILNCaP15, from LNCaP cells under androgen-deprived conditions. Unlike most pre-existing CRPC cell lines, both cell lines expressed higher levels of androgen receptor (AR) and prostate-specific antigen (PSA) than parental LNCaP cells. Moreover, these cells exhibited primary resistance to enzalutamide. Since AR signaling plays a significant role in the development of CRPC, PSA promoter sequences fused with GFP were introduced into AILNCaP14 cells to conduct GFP fluorescence-based chemical screening. We identified flavopiridol, a broad-spectrum CDK inhibitor, as a candidate drug that could repress AR transactivation of CRPC cells, presumably through the inhibition of phosphorylation of AR on the serine 81 residue (pARSer81 ). Importantly, this broad-spectrum CDK inhibitor inhibited the proliferation of AILNCaP14 cells both in vitro and in vivo. Moreover, a newly developed liver metastatic model using AILNCaP15 cells revealed that the compound attenuated tumor growth of CRPC harboring highly metastatic properties. Finally, we developed a patient-derived xenograft (PDX) model of CRPC and DCaP CR from a patient presenting therapeutic resistance to enzalutamide, abiraterone, and docetaxel. Flavopiridol successfully suppressed the tumor growth of CRPC in this PDX model. Since ARSer81 was found to be phosphorylated in clinical CRPC samples, our data suggested that broad-spectrum CDK inhibitors might be a potent candidate drug for the treatment of CRPC, including those exhibiting primary resistance to enzalutamide.

THU496 A Positive Relationship Exists Between CARF And AR In Prostate Cancer

Abstract Disclosure: K.M. Hasan: None. H. Khambati: None. R.R. Huerta: None. J. Vadgama: None. A.P. Sinha-Hikim: None. T.C. Friedman: None. Prostate cancer (PCa) is the second most prevalent cancer among men worldwide. Since PCa onset is androgen dependent, androgen deprivation therapy (ADT) is the first treatment choice for a primary tumor or metastatic PCa. However, ADT eventually leads to the development of castration resistant PCa (CRPC), which is the leading cause of higher mortality in PCa. Thus, there is a need to identify the underlying mechanisms of CRPC to manage this aggressive disease. Increased androgen receptor (AR) expression is one of the most important factors contributing to the development of CRPC. It has been shown that tumor suppressor p53 negatively regulates the expression of AR. So, loss of p53 functions has been associated with increased expression of AR in advanced PCa. However, the mechanism of p53-mediated inhibition of AR is not well understood. In this study, we demonstrated that CARF (CDKN2AIP), a p53 pathway regulatory protein, is highly expressed in PCa, but its significance in PCa development is unknown. Since, like AR, CARF is negatively regulated by p53, we hypothesize that a reciprocal relationship between CARF and p53 could regulate AR expression in PCa cells. Indeed, we found that activation of p53 by DNA damage stress inhibited both CARF and AR in LnCap and 22RV1, AR-positive, and wtp53 cell lines. Our result indicated that CARF and AR were decreased dose-dependent manner, and presumably, that could trigger cell death. Consistent with this speculation, we found that silencing CARF by ShRNA in LnCap triggered apoptosis and inhibition of cell proliferation. With great interest, we further demonstrated that silencing of CARF downregulated the AR level in LnCap and 22RV1 cells suggesting that CARF regulates the expression of AR in PCa. RT-PCR results showed that AR transcripts remained unchanged in CARF-depleted LnCap cells. This result indicated that CARF could regulate the AR stability but not the transcription. Intriguingly, we found that the expression of NEDD4, one of the AR-targeting E3 ligases, was increased in CARF-depleted cells. Therefore, by enhancing the stability, CARF could positively regulate the expression of AR in PCa cells. Further studies are in progress to know more details about the CARF-mediated AR regulation and its impact on androgen-independent PCa development and progression. Presentation: Thursday, June 15, 2023

IGF-1 axis changes with ADT and docetaxel in metastatic prostate cancer.

Androgen deprivation therapy (ADT) forms the cornerstone of treatment in locally advanced and metastatic prostate cancer (PCa). Since the growth hormone-insulin-like growth factor (GH-IGF-1) axis has been implicated in prostate tumorigenesis, we aimed to evaluate the association between IGF-1 and its binding proteins on outcomes in men with metastatic PCa treated with ADT, with or without docetaxel (D). We analyzed serum samples for IGF-1 and its family proteins from baseline, 6 months post-randomization, and at the time of progression in men enrolled to receive ADT +/- D in the phase 3 CHAARTED trial. The key outcomes were time to the development of castrate-resistant prostate cancer and overall survival (OS). About 560 patients had samples available for analysis. At 6 months, significant increases in IGF-BP1 (mean Δ+27.4%, P = 0.033), IGF-BP3 (mean Δ+10.3%, P < 0.001), and IGF-BP4 (mean Δ+31.1%, P < 0.001) were seen in the ADT + D group, while the ADT group showed an increase in IGF-BP3 (mean Δ+5.5%, P = 0.015). A higher IGF-1:IGF-BP1 ratio at baseline and after 6 months was associated with improved OS in both the ADT (baseline: hazard ratio (HR) = 0.77, P = 0.026; 6 months: HR = 0.83, P = 0.036) and ADT + D groups (baseline: HR = 0.78, P = 0.04; 6 months: HR = 0.81, P = 0.018). Patients with a log10IGF-1:IGF-BP1 ratio >1.3 at baseline had improved OS when meta-analyzed with data from a prior cohort (HR = 0.71). A higher baseline and 6-month IGF-1:IGF-BP1 ratio was associated with better OS. Further exploration of the IGF-1 axis will be important to assess its role as a predictive biomarker and to target this axis in therapeutic trials.

The Critical Interplay of CAF Plasticity and Resistance in Prostate Cancer.

Prostate cancer is a common malignancy driven by the androgen receptor (AR) pathway, with androgen deprivation therapy (ADT) being a standard treatment. However, the development of castration-resistant prostate cancer (CRPC) poses a significant challenge. CRPC is characterized by significantly increased tumor heterogeneity and lineage plasticity. Current research has primarily emphasized intrinsic tumor mechanisms, paying less attention to the role of the tumor microenvironment in cancer recurrence and drug resistance. In their recent study published in Cancer Cell, Wang and colleagues used single-cell RNA sequencing in genetically engineered mouse models with prostate tumors at different stages. They revealed that SPP1+ myofibroblastic cancer-associated fibroblasts (myCAF), induced by ADT, play an instrumental role in CRPC development. Their work also underscores the association between therapy-induced phenotypic alterations of CAFs and disease progression. This discovery highlights the potential for stromal compartment targeting as a means to mitigate CRPC development and overcome treatment resistance.

Spinal Instability as a Prognostic Factor in Patients With Spinal Metastasis of Castration-resistant Prostate Cancer.

To evaluate the Spinal Instability Neoplastic Score (SINS) for prediction of survival in patients with spinal column metastasis of castration-resistant prostate cancer (CRPC). A retrospective study of spinal instability was performed in patients with CRPC using SINS. Overall survival was evaluated starting from the time of SINS evaluation. The subjects were 42 patients with CRPC among 261 cases diagnosed with metastatic spinal tumors by radiologists, among 42,152 cases that underwent a body computed tomography scan at Kawasaki Medical School Hospital within 32 months from December 2013 to July 2016. The median age was 78 (range=55-91 years), the median prostate-specific antigen (PSA) level at SINS evaluation was 42.1 (0.1-3,121.6) ng/ml, and 11 patients had visceral metastasis. The median periods from diagnosis of bone metastasis and development of CRPC to SINS evaluation were 17 (0-158) and 20 (0-149) months, respectively. The spine was stable in 32 cases (group S) and potentially unstable or unstable in 10 (24%) (group U). The median observation period was 17.5 (0-83) months and 36 patients died. The median survival period after SINS evaluation was longer in group S than that in group U (20 vs. 10 months, p=0.0221). In multivariate analysis, PSA level, visceral metastasis, and spinal instability were significant prognostic factors. The hazard ratio for patients in group U was 2.60 (95%CI=1.07-5.93, p=0.0345). Spinal stability evaluated using SINS is a new prognostic factor for survival of patients with spinal metastasis of CRPC.

Lineage plasticity and treatment resistance in prostate cancer: the intersection of genetics, epigenetics, and evolution.

Androgen deprivation therapy is a cornerstone of treatment for advanced prostate cancer, and the development of castrate-resistant prostate cancer (CRPC) is the primary cause of prostate cancer-related mortality. While CRPC typically develops through a gain in androgen receptor (AR) signaling, a subset of CRPC will lose reliance on the AR. This process involves genetic, epigenetic, and hormonal changes that promote cellular plasticity, leading to AR-indifferent disease, with neuroendocrine prostate cancer (NEPC) being the quintessential example. NEPC is enriched following treatment with second-generation anti-androgens and exhibits resistance to endocrine therapy. Loss of RB1, TP53, and PTEN expression and MYCN and AURKA amplification appear to be key drivers for NEPC differentiation. Epigenetic modifications also play an important role in the transition to a neuroendocrine phenotype. DNA methylation of specific gene promoters can regulate lineage commitment and differentiation. Histone methylation can suppress AR expression and promote neuroendocrine-specific gene expression. Emerging data suggest that EZH2 is a key regulator of this epigenetic rewiring. Several mechanisms drive AR-dependent castration resistance, notably AR splice variant expression, expression of the adrenal-permissive 3βHSD1 allele, and glucocorticoid receptor expression. Aberrant epigenetic regulation also promotes radioresistance by altering the expression of DNA repair- and cell cycle-related genes. Novel therapies are currently being developed to target these diverse genetic, epigenetic, and hormonal mechanisms promoting lineage plasticity-driven NEPC.

Abstract A026: BMX inhibition reverses HSD3B1-driven resistance in prostate cancer

Abstract Background: Prostate cancer is the second leading cause of cancer-related death in men in the United States and is dependent on androgens and androgen receptor (AR) activation. Androgen deprivation therapy (ADT) is the mainstay treatment, but it as well as next-generation treatments eventually fail. Disease then progresses as castration-resistant prostate cancer (CRPC), which is driven by reactivation of the androgen-AR axis. 3β-hydroxysteroid dehydrogenase-1 (3βHSD1) catalyzes the rate-limiting step for potent androgen synthesis from adrenal-derived precursors, thereby stimulating CRPC. HSD3B1, which encodes for 3βHSD1, has a common missense-encoding germline variation that enhances conversion from adrenal DHEA to potent androgens. Clinical studies demonstrate that this “adrenal-permissive” HSD3B1 genotype confers more rapid progression on ADT, and recent studies show that overall survival is shorter in patients with the adrenal-permissive genotype who are treated with ADT + enzalutamide. The Etk/BMX kinase may be involved in the development and progression of CRPC. We sought to determine whether phosphorylation of 3βHSD1 is required for its activation and that the necessary kinase could be a potential target. Methods: In prostate cancer lines, mouse xenograft models, and fresh patient prostatectomy tissues, mass spectrometry and HPLC were used to identify steroid metabolites. Genetic and pharmacological methods were used to identify inhibition of BMX-mediated 3βHSD1 phosphorylation in CRPC. Results: BMX inhibition suppressed castration-resistant prostate cancer through targeting 3βHSD1 phosphorylation. 3βHSD1 transcription level and enzyme activity were induced in enzalutamide-resistant prostate cancer cell lines. 3βHSD1 and SF-1 transcription levels were positively correlated in prostate adenocarcinoma (TCGA database). BMX inhibition by zanubrutinib suppressed enzalutamide resistance induced 3βHSD1 enzyme activity. Conclusions: BMX promotes CRPC by regulating 3βHSD1 phosphorylation. BMX inhibition has potential as a new therapy to optimize CRPC treatment. Citation Format: Xiuxiu Li, Michael Berk, Christopher Goins, Mohammad Alyamani, Yoon-Mi Chung, Chenyao Wang, Monaben Patel, Nityam Rathi, Ziqi Zhu, Belinda Willard, Shaun Stauffer, Eric Klein, Nima Sharifi. BMX inhibition reverses HSD3B1-driven 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 A026.

Castration-resistant prostate cancer (CRPC) on PSMA-PET: Imaging features, disease distribution, and a comparison to castration-sensitive prostate cancer (CSPC).

e17062 Background: 18F-DCFPyL PET/CT is increasingly used in the staging and response assessment of patients (pts) with prostate cancer. Recent studies suggest that short-term ADT increases prostate-specific membrane antigen (PSMA) expression, whereas long-term ADT suppresses PSMA. Changes in PSMA expression after the development of CRPC are uncertain. We described 18F-DCFPyL PET findings in pts with CRPC and compared them to findings in CSPC. Methods: We analyzed 538 18F-DCFPyL scans performed at our large academic center. CRPC was defined as rising PSA w/ testosterone &lt; 50 ng/dL on ADT. M0 CRPC was defined as absence of extra-pelvic disease (dz) and oligometastatic CRPC (oCRPC) was defined as ≤ 5 LN + osseous lesions and absence of visceral dz. Highest SUV max (hSUVmax) was abstracted from radiologist impression. Means between groups were compared using two-tailed t-tests; undetectable PSA levels were scored as “0”. Logistic regression was used to compare dz distribution between castrate states. Significance was defined as p &lt; 0.05. Results: There were 81 pts with CRPC, 72 pts with metastatic CRPC (mCRPC) and 123 pts with mCSPC. The median ages of pts with mCRPC (74.5 years) and mCSPC (71) were similar. The mean PSAs of mCSPC (20.2 ng/mL) and mCRPC (69.4) were significantly different. hSUVmax was higher in mCRPC (mean 40.3, 95% CI 32.7 – 47.8) than in mHSPC (22.6, 18.4 – 26.9), p &lt; 0.001. Distribution of mCRPC lesions was as follows: prostate bed (26.4%), local pelvic LN (25%), distant LN (M1a, 41.7%), osseous (M1b, 16.7%), and visceral (M1c, 16.7%). In a multivariate analysis mCRPC pts had lower rates of pelvic LN dz and higher rates of M1c, with a trend toward increased M1b (p &lt; 0.10), compared to mCSPC pts. ADT and androgen pathway inhibition did not affect hSUVmax in CRPC. Within CRPC, there were 9 pts with M0 dz, 24 pts with oCRPC, and 48 pts with polymetastatic dz (pmCRPC). The ages (Table) of pmCRPC and oCRPC pts were similar. The mean PSA of pmCRPC (100.9) was higher than that of oCRPC (8.8) and M0 CRPC (5.7). hSUVmax between oCRPC (40.3) and pmCRPC (40.3) was similar. Conclusions: The greater hSUVmax in mCRPC may implicate the effect of ADT on PSMA expression or may describe differing tumor biology. mCRPC pts had less local dz and more frequent distant metastases, likely reflecting more advanced disease. These findings will help inform detection of developing castrate resistance on PSMA-PET. More data are needed on the classification of oligometastatic dz on PSMA-PET and the impact of hormone therapy on PSMA in CRPC. [Table: see text]

TRAF4-mediated nonproteolytic ubiquitination of androgen receptor promotes castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) poses a major clinical challenge with the androgen receptor (AR) remaining to be a critical oncogenic player. Several lines of evidence indicate that AR induces a distinct transcriptional program after androgen deprivation in CRPCs. However, the mechanism triggering AR binding to a distinct set of genomic loci in CRPC and how it promotes CRPC development remain unclear. We demonstrate here that atypical ubiquitination of AR mediated by an E3 ubiquitin ligase TRAF4 plays an important role in this process. TRAF4 is highly expressed in CRPCs and promotes CRPC development. It mediates K27-linked ubiquitination at the C-terminal tail of AR and increases its association with the pioneer factor FOXA1. Consequently, AR binds to a distinct set of genomic loci enriched with FOXA1- and HOXB13-binding motifs to drive different transcriptional programs including an olfactory transduction pathway. Through the surprising upregulation of olfactory receptor gene transcription, TRAF4 increases intracellular cAMP levels and boosts E2F transcription factor activity to promote cell proliferation under androgen deprivation conditions. Altogether, these findings reveal a posttranslational mechanism driving AR-regulated transcriptional reprogramming to provide survival advantages for prostate cancer cells under castration conditions.