Prostate Cancer Cell Models Research Articles

P099 Effect of the PARP inhibitor talazoparib in combination with radiation and enzalutamide in prostate cancer cell models

P099 Effect of the PARP inhibitor talazoparib in combination with radiation and enzalutamide in prostate cancer cell models

Enhancing Effects of Olaparib by Alpha- and Beta-Emitting Radionuclides, X-Rays, and Ultraviolet A Light in Combination with Ortho-IodoHoechst in a Prostate Cancer Cell Model

Background: New therapeutic strategies for metastatic castration-resistant prostate cancer (mCRPC) have been developed in the past to achieve the best response rates. Most recently, the use of combination therapies has been explored to optimize patient outcomes. Poly(ADP-ribose) polymerase inhibitors (PARPi) may help to treat mCRPC more effectively. Objectives: This study aimed to determine whether the combination of a PARPi with different radiation qualities results in different levels of radiosensitization of PC-3 cells. Methods: The radiosensitizing potential of Olaparib in combination with 177Lu, 223Ra, X-rays and photodynamic therapy (PDT) using the UVA light-activated photosensitizer ortho-iodoHoechst33258 (oIH) was evaluated by determining the clonogenic survival, DNA damage and cell cycle analysis. Results: Here, we show that this combination strategy differentially sensitized PC-3 cells to different radiation qualities. The combination of 177Lu with Olaparib increased the numbers of persistent double-strand breaks (DSBs) by a factor of 3.3 and cell death in PC-3 cells. Overall, the β-emitter 177Lu indicated a higher radiosensitization efficacy compared to 223Ra, with X-rays corresponding to dose modification factors (DMF) of 1.77, 1.17 and 1.16 respectively. Even in the case of the α-emitter 223Ra, the effects were much less pronounced than for 177Lu. PARPi also showed a slight potentiation of the cytotoxic effects both in co-treatment with X-rays and with PDT. Conclusions: The results of our study indicate a potential role for Olaparib in further optimizing the PSMA radioligand therapy (PRLT) outcomes. However, further evaluation of the combination of PARPi with PRLT is needed to gain more insights into improving the benefit to patients suffering from mCRPC.

SRSF6 modulates histone-chaperone HIRA splicing to orchestrate AR and E2F activity in prostate cancer.

Despite novel therapeutic strategies, advanced-stage prostate cancer (PCa) remains highly lethal, pointing out the urgent need for effective therapeutic strategies. While dysregulation of the splicing process is considered a cancer hallmark, the role of certain splicing factors remains unknown in PCa. This study focuses on characterizing the levels and role of SRSF6 in this disease. Comprehensive analyses of SRSF6 alterations (copy number/mRNA/protein) were conducted across eight well-characterized PCa cohorts and the Hi-MYC transgenic model. SRSF6 was up-regulated in PCa samples, correlating with adverse clinical parameters. Functional assays, both in vitro (cell proliferation, migration, colony, and tumorsphere formation) and in vivo (xenograft tumors), demonstrated the impact of SRSF6 modulation on critical cancer hallmarks. Mechanistically, SRSF6 regulates the splicing pattern of the histone-chaperone HIRA, consequently affecting the activity of H3.3 in PCa and breast cancer cell models and disrupting pivotal oncogenic pathways (AR and E2F) in PCa cells. These findings underscore SRSF6 as a promising therapeutic target for PCa/advanced-stage PCa.

Abstract C098: CYR61 expression in prostate cancer patients at City of Hope

Abstract In the US, African-American (AA) and Hispanic/Latino (H/L) men have higher rates of advanced prostate cancer (PCa), increased PCa-specific mortality, and are more likely to undergo metastasis than non-Hispanic White (NHW) men attributed to a lack of access to early screening, and a higher prevalence of risk factors such as obesity, diet, and genetic differences. Consequently, effective treatment of advanced PCa and elimination of racial and ethnic disparities for this malignancy require the identification of mechanisms of disease progression. In PCa, the cysteine-rich angiogenic inducer 61 (CYR61) contributes to malignant cell growth through interactions with extracellular ligands, such as integrins avb3 and a6b4. In previous studies, we have found that CYR61 is upregulated in metastatic PCa cell lines and knockdown of this protein significantly reduced metastatic cell proliferation, viability, prostasphere formation, and activation of the PI3/AKT pathway, indicating a potential utilization of CYR61 inhibition in the therapy of metastatic PCa. Interestingly, we have observed that in metastatic PCa cell models, IGF1 induction increased CYR61 protein expression. However, the correlation between PCa aggressiveness and levels of CYR61 in tumor-derived tissues from patients is poorly studied. Our goal with this study is to identify possible correlations in CYR61 expression that may reflect health disparities in PCa outcomes. We used in silico analyses from whole exome paired tumor/normal DNA sequencing and tumor RNA sequencing data available on 542 PCa cases in the City of Hope POSEIDON database to determine whether gene expression of CYR61 and IGF1 was correlated with genetic ancestry, Gleason score, and tumor purity. In univariate analyses, we found that H/L PCa cases had significantly higher levels of expression of CYR61 than NHW PCa cases (p = 0.043) and that both H/L and AA PCa cases had higher IGF1 expression levels, although only significant in AA (p=0.031). We also found that PCa patients with Gleason scores of 8 and higher had significantly lower expression of IGF1 than those with Gleason scores of 7 or less (p=0.006). Both CYR61 and IGF1 expression levels were significantly lower in those with luminal B (p=0.00000000053, p=0.000009, respectively) and with basal subtypes (p=0.00035, p=0.000069, respectively compared to luminal A subtype. Tumor purity was estimated by RNA-seq based on 141 genes specific to stroma and 141 genes specific to immune cells. CYR61 expression was significantly correlated with stromal and immune infiltration. These results suggest that reduced CYR61 expression is associated with more aggressive PCa. Additional analyses are ongoing to understand the interplay of variables of race and ethnicity, age, Gleason score, and tumor purity and to investigate outcomes of biochemical recurrence and death from PCa. Citation Format: Greisha L. Ortiz-Hernandez, Yuan Chun Ding, Susan L. Neuhausen. CYR61 expression in prostate cancer patients at City of Hope [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C098.

Abstract C097: PVT1 exon 9-dependent overexpression of RSAD2 is a characteristic of prostate cancer in males of African ancestry

Abstract Aggressive prostate cancer (PCa), including castrate-resistant and neuroendocrine subtypes, is projected to increase in incidence 5% each year. Aggressive PCa disproportionally impacts African American men, has limited effective treatment options and high mortality rates. Although racial disparities are established in PCa development, attributed to multiple contributory factors including systemic racism, differences in socioeconomic status and distrust in the medical system, work is still needed to understand the contribution of biological factors. We found the exon 9 region of plasmacytoma variant translocation 1 (PVT1) overexpressed in aggressive PCa cell lines derived from African American (AA) men. We found PVT1 exon 9 overexpression induced phenotypic changes to normal prostate epithelial cells in vitro and led to tumor formation in vivo. RNA-sequencing analysis revealed 156 significantly differentially expressed genes influenced by PVT1 exon 9 overexpression and radical S-adenosyl methionine domain containing 2 (RSAD2) was the top significantly overexpressed gene (log2Fold change 1.71, p-value < 0.05). We utilized the GSE223405 publicly available dataset to identify whether our identified PVT1 exon 9 downstream genes were enriched in AA prostate cancer cells. RSAD2 was significantly overexpressed in AA prostate cancer cells compared to prostate cancer cells from men of European ancestry (moEA) (log2Fold change 6.18, p-value < 0.05). Comparing normal cells to prostate cancer cells between these groups, we found that normal AA prostate cells had significantly higher expression of RSAD2 (log2fold change 4.25, p-value < 0.001) whereas moEA samples did not (log2fold change 0.837, p-value=0.150). From analysis of data obtained from cBioPortal, we found RSAD2 alteration significantly correlates (p-value < 0.001) with self-identified race and copy number overexpression of RSAD2 was found to be enriched in AA patients (18.16% moEA versus 24% AA). Finally, we found 88.6% of the significantly differentially expressed genes within our PVT1 exon 9 RNA-sequencing dataset were significantly differentially expressed in GSE223405 AA samples and of those, 51.7% of genes exhibited a similar differential expression pattern suggesting that the PVT1 exon 9/RSAD2 dependent pathway may be more prominent in AA men. Mechanistically, we found two differing pathways of RSAD2 overexpression in aggressive prostate cancer cell models, one dependent and one independent of PVT1 exon 9 overexpression, with similar but differing biological functions related to epigenetic processes and metabolism. Ongoing work is investigating the RSAD2 and PVT1 exon 9 expression axis in a diverse set of human prostate cancer tissues and investigating their utilization as a therapeutic target in prostate cancer. Citation Format: Rachel E. Sexton-Bonacci1, Murtaza Barkarar1, Chindeum Udekwu1, Olorunseun O. Ogunwobi1. PVT1 exon 9-dependent overexpression of RSAD2 is a characteristic of prostate cancer in males of African ancestry [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr C097.

Inhibition of the Sterol Regulatory Element Binding Protein SREBF-1 Overcomes Docetaxel Resistance in Advanced Prostate Cancer

Resistance to anti-androgens and chemotherapy (Cx) limits therapeutic options for patients with hormone-sensitive (mHSPC) and hormone-resistant prostate cancer (mCRPC). In this context, upregulation of the glucocorticoid receptor (GR) has been identified as a potential bypass mechanism in mCRPC, and a combination of docetaxel and mifepristone (Doc + RU-486), an inhibitor of GR, re-sensitized docetaxel-resistant cell models to Cx. This study was designed to elucidate the molecular mechanisms responsible for this phenomenon. RNA sequencing (RNA-seq) in docetaxel-resistant PCa cell models after Doc + RU-486 treatment with consecutive functional assays were performed. Expression of selected proteins was verified in prostatic tissue from prostate cancer (PCa) patients with progressive disease. Treatment with Doc + RU-486 significantly reduced cancer cell viability and RNA-Seq. revealed sterol regulatory element of binding transcription factor 1 (SREBF-1), a transcription factor of cholesterol and lipid biosynthesis, as a significantly downregulated target. Functional assays confirmed that SREBF-1 downregulation is partially responsible for this observation. In concordance, SREBF-1 knockdown and pharmacological SREBP inhibition, together with other key enzymes in the cholesterol pathway, showed similar results. Furthermore, SREBF-1 expression is significantly elevated in advanced PCa tissues, demonstrating its potential involvement in tumor progression and emerging therapy resistance. Therefore, specific inhibition of cholesterol and lipid biosynthesis might also target Cx-resistant cancer cells and represent a potential additive future therapeutic option to improve mCRPC therapy.

AI Based Discovery of a New AKR1C3 Inhibitor for Anticancer Applications.

AKR1C3 is an upregulated enzyme in prostate and other cancers; in addition to regulating hormone synthesis, this enzyme is thought to play a role in the aggressiveness of tumors and in the defense against drugs. We here used an unbiased method to discover new potent AKR1C3 inhibitors: through an AI-based virtual drug screen, compound 4 was identified as a potent and selective enzymatic inhibitor able to translate this activity into a pronounced antiproliferative effect in the 22RV1 prostate cancer cell model. As other known AKR1C3 inhibitors, compound 4 determined a significantly increased activity of abiraterone, a drug approved for advanced prostate cancer. Compound 4 also showed a synergic effect with doxorubicin in osteosarcoma cell lines; specifically, the effect is correlated with AKR1C3 expression. In this research work, therefore, the use of AI allowed the identification of a new structure as an AKR1C3 inhibitor and its potential to enhance the effect of chemotherapeutics.

Characterization of structural, biochemical, pharmacokinetic, and pharmacodynamic properties of the LSD1 inhibitor bomedemstat in preclinical models.

Lysine-specific demethylase 1 (LSD1) is emerging as a critical mediator of tumor progression in metastatic castration-resistant prostate cancer (mCRPC). Neuroendocrine prostate cancer (NEPC) is increasingly recognized as an adaptive mechanism of resistance in mCRPC patients failing androgen receptor axis-targeted therapies. Safe and effective LSD1 inhibitors are necessary to determine antitumor response in prostate cancer models. For this reason, we characterize the LSD1 inhibitor bomedemstat to assess its clinical potential in NEPC as well as other mCRPC pathological subtypes. Bomedemstat was characterized via crystallization, flavine adenine dinucleotide spectrophotometry, and enzyme kinetics. On-target effects were assessed in relevant prostate cancer cell models by measuring proliferation and H3K4 methylation using western blot analysis. In vivo, pharmacokinetic (PK) and pharmacodynamic (PD) profiles of bomedemstat are also described. Structural, biochemical, and PK/PD properties of bomedemstat, an irreversible, orally-bioavailable inhibitor of LSD1 are reported. Our data demonstrate bomedemstat has >2500-fold greater specificity for LSD1 over monoamine oxidase (MAO)-A and -B. Bomedemstat also demonstrates activity against several models of advanced CRPC, including NEPC patient-derived xenografts. Significant intra-tumoral accumulation of orally-administered bomedemstat is measured with micromolar levels achieved in vivo (1.2 ± 0.45 µM at the 7.5 mg/kg dose and 3.76 ± 0.43 µM at the 15 mg/kg dose). Daily oral dosing of bomedemstat at 40 mg/kg/day is well-tolerated, with on-target thrombocytopenia observed that is rapidly reversible following treatment cessation. Bomedemstat provides enhanced specificity against LSD1, as revealed by structural and biochemical data. PK/PD data display an overall safety profile with manageable side effects resulting from LSD1 inhibition using bomedemstat in preclinical models. Altogether, our results support clinical testing of bomedemstat in the setting of mCRPC.

Abstract 6282: Novel androgen related gene network in prostate cancer cell model

Abstract Prostate cancer stands as the foremost cause of cancer-related deaths among men in the United States, with the primary treatment being androgen receptor (AR) antagonists relying on current androgen signaling knowledge. Most of this knowledge is derived from next-generation sequencing experiments, but the oversight of splice variants and highly similar sequences in multiple loci can hinder a comprehensive understanding. In an effort to unveil the complete androgen receptor transcriptional program, we employed a novel sequencing analysis protocol. Using a R1881-LNCaP model, we identified 212 upregulated and 92 downregulated genes, of which a notable one-third (68 upregulated and 39 downregulated) had not been previously associated with androgen. Among these novel transcripts, 5.6% lacked splice variants, while 16.3% exhibited one or more splice variants, including 3.8% from seven unique gene families. Recognized androgen-regulated genes, such as ORM1, STEAP4, NPPC, ORM2, and KLK3, were validated as upregulated, while GRB10, FN1, PPFIA2, and PLA2G2A were confirmed as downregulated in this in-vitro model. Utilizing chromatin immunoprecipitation-sequencing (ChIP-seq) data, we found that 13% of the genes contained at least one androgen response element within 5 kb upstream or downstream. Further validation through real-time PCR confirmed the expression levels of 90% of the selected genes (18). Ingenuity Pathway Analysis revealed two major regulators (ESRRA and ARFGEF2) in causal networks likely interacting with the novel genes. Intriguingly, 57.1% of ESRRA-involved genes contained at least one ESRRA binding site in a ChIP-seq dataset. Although ESRRA is known to activate androgen biosynthesis in castration-resistant prostate cancer, its interaction with AR and co-regulation of androgen signaling remain unknown. Ongoing studies involve the characterization of these networks in prostate cancer cell lines, examining anchorage-independent capacity, invasion, migration, proliferation, and progression. Data collection and comparison will ascertain whether the signaling is driven by mutated AR, and the role of ARv7 will be elucidated through gene lockdown experiments. Citation Format: Alex L. McDonald, Spencer Snow, Shuk-mei Ho, Yuet-kin Leung. Novel androgen related gene network in prostate cancer cell model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6282.

Abstract C061: The impact of the BRG1/BRM-associated factor (BAF) complex on the androgen receptor cistrome in African American prostate cancer

Abstract We aimed to establish in prostate cancer (PCa) how and why the androgen receptor displays differential functions in a manner driven by genomic ancestry, namely between African American (AA) and European American (EA) PCa, with the goal to assess how this may contribute to PCa health disparities. We utilized EA and AA non-malignant prostate and PCa cell models with confirmed genomic ancestry and defined the basal and dihydrotestosterone (DHT)-regulated AR and H3K27ac cistromes using CUT&RUN, and integrated these data with publicly available genomic counterparts. The DHT-dependent AR and H3K27ac cistromes significantly overlapped within AA cells and EA cells but there was significantly less overlap between AA and EA cells. For example, H3K27ac distributions were frequent (~15-20k sites) in each of non-malignant AA RC43N and EA HPr1AR, and malignant RC43T and LNCaP, and the significance of the overlaps were comparable for basal and DHT treated cells, but this was not significantly impacted by ancestry. By contrast the AR cistrome was highly DHT-dependent, with ~2k sites notably in LNCaP and RC43T, which very significantly overlapped with H3K27ac in the same cells but significantly less so across cells. Thus, although the H3K27ac cistrome was comparable across cells, the overlap with AR was driven by genomic ancestry. To investigate this, we focused on the BAF complexes as previously we identified reduced expression of a key component, SMARCA5, in AA PCa. These large multimeric complexes regulate nucleosome positioning during gene transcription and DNA repair. In PCa, the cBAF complex impacts different transcription factors, including ERG, and it is tempting to speculate that the corruption of cBAF identified in AA PCa phenocopies the impact of TMPRSS2-ETS impact observed in EA PCa. To test the possibility that the cBAF complex corrupts AR genomic functions in AA PCa we exploited scRNA-Seq data from PCa organoids from the Rb and Pten double knockout (PBCre4:Rb1f/f:Pten f/f ) to establish that expression of genes in the cBAF genes complex were collectively significantly altered in neuroendocrine PCa (NEPC) and Pouf23 androgen indifferent lineages. Secondly, knockdown of another cBAF component, SMARCC1, enhanced Enzalutamide sensitivity in same organoids. Finally, to test the impact of cBAF complex on AR signaling we have generated AA and EA PCa cell lines that stably express dCRISPR-activator (VP64) or repressor (KRAB) proteins and designed gRNAs to regulate expression of, for example, SMARCA5 and measure the impact on the AR cistrome and function. In summary, these findings identified that the shared AR and H3K27ac cistromes are driven by genomic ancestry, and that reduced expression of SMARCA5 and other components of the cBAF complex are significant in AA and advanced PCa, and impact AR signaling. Our future directions are focused on how SMARCA5 expression disrupts the balance between transcription factor functions, such as for the AR and other transcription factors, and effective DNA repair. Citation Format: Shahid S. Hussain, Debasis Nayak, David W. Goodrich, Clayton Yates, Moray Campbell. The impact of the BRG1/BRM-associated factor (BAF) complex on the androgen receptor cistrome in African American prostate cancer [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr C061.

Glucocorticoid treatment influences prostate cancer cell growth and the tumor microenvironment via altered glucocorticoid receptor signaling in prostate fibroblasts

Despite significant therapeutic advances in recent years, treatment of metastatic prostate cancer (PCa) remains palliative, owing to the inevitable occurrence of drug resistance. There is increasing evidence that epithelial glucocorticoid receptor (GR) signaling and changes in the tumor-microenvironment (TME) play important roles in this process. Since glucocorticoids (GCs) are used as concomitant medications in the course of PCa treatment, it is essential to investigate the impact of GCs on stromal GR signaling in the TME. Therefore, general GR mRNA and protein expression was assessed in radical prostatectomy specimens and metastatic lesions. Elevated stromal GR signaling after GC treatment resulted in altered GR-target gene, soluble protein expression, and in a morphology change of immortalized and primary isolated cancer-associated fibroblasts (CAFs). Subsequently, these changes affected proliferation, colony formation, and 3D-spheroid growth of multiple epithelial PCa cell models. Altered expression of extra-cellular matrix (ECM) and adhesion-related proteins led to an ECM remodeling. Notably, androgen receptor pathway inhibitor treatments did not affect CAF viability. Our findings demonstrate that GC-mediated elevated GR signaling has a major impact on the CAF secretome and the ECM architecture. GC-treated fibroblasts significantly influence epithelial tumor cell growth and must be considered in future therapeutic strategies.

Tricyclic Diterpenoids Selectively Suppress Androgen Receptor-Positive Prostate Cancer Cells.

Androgen receptor (AR) is a viable therapeutic target for lethal castration-resistant prostate cancer (CRPC), because the continued progression of CRPC is mainly driven by the reactivation of AR transcriptional activity. The current FDA-approved AR antagonists binding to ligand binding domain (LBD) become ineffective in CRPC with AR gene amplification, LBD mutation, and the evolution of LBD-truncated AR splice variants. Encouraged by the fact that tricyclic aromatic diterpenoid QW07 has recently been established as a potential N-terminal AR antagonist, this study aims to explore the structure-activity relationship of tricyclic diterpenoids and their potential to suppress AR-positive cell proliferation. Dehydroabietylamine, abietic acid, dehydroabietic acid, and their derivatives were selected, since they have a similar core structure as QW07. Twenty diterpenoids were prepared for the evaluation of their antiproliferative potency on AR-positive prostate cancer cell models (LNCaP and 22Rv1) using AR-null cell models (PC-3 and DU145) as comparisons. Our data indicated that six tricyclic diterpenoids possess greater potency than enzalutamide (FDA-approved AR antagonist) towards LNCaP and 22Rv1 AR-positive cells, and four diterpenoids are more potent than enzalutamide against 22Rv1 AR-positive cells. The optimal derivative possesses greater potency (IC50 = 0.27 µM) and selectivity than QW07 towards AR-positive 22Rv1 cells.

Abstract A005: Androgen receptor variants mRNA absolute quantification in prostate cancer cell models

Abstract Background: Patients treated with Androgen Deprivation Therapy (ADT) have been shown to increase the expression of constitutively active Androgen Receptor (AR) splice variants (AR-Vs). These splice variants lack the ligand binding domain at the C-terminus of AR, required for binding to antiandrogen therapies. AR-V7 has also been correlated to the development and progression of castration resistant prostate cancer (CRPC). As not all circulating tumor cells (CTCs) contain AR-V7, we hypothesized that other AR-Vs are involved in the mechanism of resistance to ADT commonly seen in CRPC. To test this, we developed an mRNA quantitative assay targeting AR-Vs and then correlated our results with a targeted mass spectrometry (MS) based protein assay. This work will provide a feasible quantification of AR-V transcripts and that may provide a stratification for predicted responses to ADT treatment in patients that could be useful to clinicians. Methods: The absolute copy number of total AR, AR-V2, AR-V7, AR-V12, and AR-V23 were determined in eight different PCa cell lines and 48 patient derived xenografts (PDXs) using qRT-PCR assays. We performed siRNA targeting of these variants to evaluate primer specificity by evaluating knockdown efficiencies. These results will be correlated to targeted MS quantification of AR-Vs in each cell model. Results: We found that the most highly expressed variants in PCa cell lines were AR-V7 and AR-V12. In the LuCaP PDX model, AR-V12 was shown to have the highest expression of the AR-Vs tested. Specificity of AR-V knockdown was tested using AD-1 (which only expresses the full- length AR transcript) and R1-D567 (which only expresses AR-V567es, an AR-V12-like variant) cell lines. Conclusions: We were able to determine the landscape of AR-V mRNA expression in eight PCa cell lines and in 48 PDX tumor samples. This data will be correlated to protein expression currently being analyzed using a targeted MS method developed in our lab. Our work will be useful to help clinicians stratify PCa patients based on their AR-V expression profiles. This will establish a prognostic biomarker program that measures AR-V proteins in real time from clinical biopsy tissues, circulating tumor cells, or exosomes and informs the clinician on which course of treatment may be effective for each patient. Establishing a CRPC biomarker other than AR-V7 that can help explain the AR-V7 negative CRPC patients could eventually improve clinical application and predictive treatment outcomes. Citation Format: Gabrianne Larson, Zoi Sychev, Stephen Plymate, Eva Corey, Justin M. Drake. Androgen receptor variants mRNA absolute quantification in prostate cancer cell models [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 A005.

Qingdai Decoction suppresses prostate cancer growth in lethal-stage prostate cancer models.

Contemporary therapy for advanced castration-resistant prostate cancer (CRPC) employs reagents such as enzalutamide and abiraterone acetate targeting the androgen receptor (AR) transcription axis only provide a temporary response and rapidly develop resistance. Additionally, neuroendocrine prostate cancer (NEPC) is an AR pathway-independent and lethal-stage prostate cancer with no standard therapy. Qingdai Decoction (QDT), a traditional Chinese medicine formula, has various pharmacological activities and was widely used for the treatment of different diseases including prostatitis which may contribute to prostate cancer development. This study aims to explore the anti-tumor role and potential mechanism of QDT on prostate cancer. CRPC prostate cancer cell models and xenograft mice models were established for research. The effect of TCMs on cancer growth and metastasis were determined by CCK-8, wound-healing assays and the PC3-xenografted mice model. The toxicity of QDT in the major organs was investigated by H&E staining. The compound-target network was analyzed with network pharmacology. The correlation of QDT targets with prostate cancer patient's prognosis was analyzed with multiple prostate cancer patient cohorts. The expression of related proteins and mRNA were detected by western blot and real-time PCR. The gene knockdown was achieved with CRISPR-Cas13 technology. By integrating functional screening, network pharmacology analysis, CRISPR-Cas13 directed RNA targeting, and molecular biology validation in different prostate cancer models and clinical prostate cancer cohorts, we found that Qingdai Decoction (QDT), a Traditional Chinese Medicine, can repress cancer growth in advanced prostate cancer models in vitro and in vivo in an AR independent manner by targeting NOS3, TGFB1, and NCOA2. This study not only identified QDT as a novel drug for lethal-stage prostate cancer treatment but also provided an extensive Integrative research paradigm for investigating the roles and mechanisms of TCMs for the treatment of other diseases.

Abstract LB133: An orally bioavailable degrader targeting androgen receptor and the splice variant in castration resistant prostate cancer

Abstract The development and progression of prostate cancer depends on androgen receptor (AR) whose sustained activity albeit the use of anti-androgen drugs accounts for one of the major mechanisms leading to drug resistance. As such, the clinical benefits of current therapeutic agents remain rather limited for the advanced prostate cancer. Given that expression of constitutively active AR variants (AR-Vs) that lack the ligand-binding domain (LBD) clinically associates with the drug resistance and poor survival, targeting both AR and the LBD-truncated AR-Vs is anticipated an effective approach to overcome therapy resistance. Here, we present Proteolysis Targeting Chimeras (PROTAC) compound ITRI-148, capable of effectively degrading both full-length and LBD-truncated AR by targeting the proteins via the N-terminal domain to Cereblon-mediated ubiquitination and degradation. Degradation of AR and AR-V7 suppresses target gene expression, and inhibits cell proliferation with accompanied apoptosis activation in AR-V7-expressing castration-resistant prostate cancer (CRPC) cell models. In vivo, this compound displays good pharmacokinetics profiles and oral bioavailability with strong antitumor efficacy towards castration-, enzalutamide-resistant CWR22Rv1 and VCaP xenograft models. These data provide compelling evidence that by targeting AR NTD for induced degradation of active AR protein variants, ITRI-148 is a promising agent for the intervention of advanced therapy-resistant prostate cancers. Citation Format: Chiu-Lien Hung, Ling-Yu Wang, Chih-Wei Fu, Hung-Chih Hsu, Hsin-Jien Kung. An orally bioavailable degrader targeting androgen receptor and the splice variant in castration resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB133.

Abstract 1448: The YAP1/TEAD and NF-Kappa B transcription factors may cooperate to mediate prostate cancer progression

Abstract Metastatic castration-resistant prostate cancer is morbid and lethal. The transcriptional coregulator YAP1 (Yes-associated protein 1) is a nuclear effector of the Hippo pathway. The Hippo pathway regulates cell growth, motility, and carcinogenesis. Here, we investigated biochemical and functional interactions between YAP1 and the nuclear factor (NF) kappa B/RELA subunit in prostate cancer cell models. We demonstrated that endogenous YAP1 and RELA form protein complexes in the cell, as revealed by co-immunoprecipitation and western blotting. Compared with control, we found that combined treatment of cells with androgen and SDF1a (stromal cell-derived factor-1 alpha) or RANKL (receptor activator of NF-kappa Β ligand) enhanced the protein-protein interaction between YAP1 and RELA, as showed by proximity ligation assay. Our confocal microscopy experiment further showed that combined SDF1a and androgen treatment augmented the YAP1 and RELA colocalization relative to single-agent. Moreover, our promoter-reporter and RNAi experiments showed that genetic silencing YAP1 or TEAD protein, a key mediator of the YAP1 transcription, significantly reduced the NF-Kappa B promoter-reporter gene activity. Also, disruption of YAP1 activity by genetic and small molecule attenuated endogenous protein-protein interaction between TEAD and RELA. Furthermore, controlled expression of MST1/STK4, a potent inhibitor of YAP1, suppressed the NF-Kappa B-promoter reporter activity. Additionally, our unbiased bioinformatics analysis of the exiting ChIP-seq (chromatin immunoprecipitation-sequencing) data identified several genes likely co-regulated by the TEAD1-4 and NF-Kappa B transcription factors. Besides, our computational analysis of the TCGA and Stand Up To Cancer (SU2C) prostate cancer data sets indicated that expression of YAP/TEAD and NF-kappa B/RELA correlates in clinical cases. These findings suggest that cooperative androgen and cytokine signaling regulates Hippo/YAP and NF-Kappa B interaction and their functions. These may have critical roles in advanced prostate cancer downstream of the Hippo pathway. Citation Format: Bekir Cinar, Marwah M. Al-Mathkour, Abdulrahman M. Dwead, Ava M. Boston, Michael S. Lewis, Carlos S. Moreno. The YAP1/TEAD and NF-Kappa B transcription factors may cooperate to mediate prostate cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1448.

Core Structure-Activity Relationship Studies of 5,7,20-O-Trimethylsilybins in Prostate Cancer Cell Models.

Silibinin, also known as silybin, is isolated from milk thistle (Silybum marianum). Silibinin has been demonstrated to be a good lead compound due to its potential to prevent and treat prostate cancer. Its moderate potency and poor pharmacokinetic profile hindered it from moving forward to therapeutic use. Our research group has been working on optimizing silibinin for the potential treatment of castration-resistant prostate cancer. Our previous studies established 5,7,20-O-trimethylsilybins as promising lead compounds as they can selectively suppress androgen receptor (AR)-positive LNCaP cell proliferation. Encouraged by the promising data, the present study aims to investigate the relationships between the core structure of 5,7,20-O-trimethylsilybin and their antiproliferative activities towards AR-positive (LNCaP) and AR-negative prostate cancer cell lines (PC-3 and DU145). The structure-activity relationships among the four different core structures (including flavanonol-type flavonolignan (silibinin), flavone-type flavonolignan (hydnocarpin D), chalcone-type flavonolignan, and taxifolin (a flavonolignan precursor) indicate that 5,7,20-O-trimethylsilybins are the most promising scaffold to selectively suppress AR-positive LNCaP prostate cancer cell proliferation. Further investigation on the antiproliferative potency of their optically enriched versions of the most promising 5,7,20-O-trimethylsilybins led to the conclusion that (10R,11R) derivatives (silybin A series) are more potent than (10S,11S) derivatives (silybin B series) in suppressing AR positive LNCaP cell proliferation.

PD04-09 COMBINATION TREATMENT WITH HSP70/STUB1 MODULATOR AND ENZALUTAMIDE YIELDS SYNERGISTIC ACTIVITY IN ADVANCED PROSTATE CANCER

You have accessJournal of UrologyCME1 Apr 2023PD04-09 COMBINATION TREATMENT WITH HSP70/STUB1 MODULATOR AND ENZALUTAMIDE YIELDS SYNERGISTIC ACTIVITY IN ADVANCED PROSTATE CANCER Pengfei Xu, Joy C. Yang, Bo Chen, Christopher Nip, Shu Ning, Allen C. Gao, Hao Shao, Jason Gestwicki, Christopher P. Evans, and Chengfei Liu Pengfei XuPengfei Xu More articles by this author , Joy C. YangJoy C. Yang More articles by this author , Bo ChenBo Chen More articles by this author , Christopher NipChristopher Nip More articles by this author , Shu NingShu Ning More articles by this author , Allen C. GaoAllen C. Gao More articles by this author , Hao ShaoHao Shao More articles by this author , Jason GestwickiJason Gestwicki More articles by this author , Christopher P. EvansChristopher P. Evans More articles by this author , and Chengfei LiuChengfei Liu More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003228.09AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Ubiquitin proteasome system is suppressed in enzalutamide resistant prostate cancer cells and that the HSP70/STUB1 machinery is involved in androgen receptor (AR) and AR variant protein stabilization. Targeting HSP70 could be a valuable strategy to overcome the resistance of androgen receptor signaling inhibitors (ARSI) in advanced prostate cancer. In this study, we tested novel HSP70/STUB1modulators in enzalutamide resistant cells and patient-derived prostate cancer cell models. METHODS: Expression of AR-V7, HSP70 and STUB1 were determined by qRT-PCR and western blot. Expression of HSP70 and STUB1 was down-regulated using specific siRNA. HSP70/STUB1 and AR-V7 interaction was determined by co-immunoprecipitation and dual immunofluorescence. Tumor organoids were established from the patient derived xenografts (PDX) and the viability was stained by LIVE/DEAD™ Cell Imaging Kit. The effects of HSP70 inhibitors on enzalutamide sensitivity were examined in cell line model and patient-derived cell models. RESULTS: A novel HSP70 inhibitor JG98 significantly suppressed drug resistant C4-2B MDVR and CWR22Rv1 cell growth and enhanced enzalutamide treatment (p<0.001). JG98 also suppressed the PDX derived organoid growth and induced organoid death in a dose dependent manner (p<0.001). Mechanistically, JG98 suppressed AR/AR-V7 expression in resistant cells and promoted STUB1 entering into the nucleus and bound to AR-V7. Knockdown of STUB1 diminished the anti-cancer effect and AR-V7 inhibition by JG98. A more potent HSP70 inhibitor JG231 was developed from JG98. JG231 significantly improved the drug solubility and showed better pharmacokinetic characteristics than JG98. Moreover, JG231 effectively suppressed the cell growth and enhanced enzalutamide treatment in resistant cells and PDX derived prostate cancer cells (p<0.001). CONCLUSIONS: The HSP70/STUB1 machinery involved in AR/AR-V7 regulation and enzalutamide resistance. Targeting HSP70 by novel HSP70/STUB1 modulators overcome the ARSI resistance and improve their therapy. Source of Funding: This work was supported in part by grants NIH/NCI R37CA249108 (C, Liu) and R01CA251253 (C, Liu) © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e145 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Pengfei Xu More articles by this author Joy C. Yang More articles by this author Bo Chen More articles by this author Christopher Nip More articles by this author Shu Ning More articles by this author Allen C. Gao More articles by this author Hao Shao More articles by this author Jason Gestwicki More articles by this author Christopher P. Evans More articles by this author Chengfei Liu More articles by this author Expand All Advertisement PDF downloadLoading ...

PI5P4Kα supports prostate cancer metabolism and exposes a survival vulnerability during androgen receptor inhibition.

Phosphatidylinositol (PI)regulating enzymes are frequently altered in cancer and have become a focus for drug development. Here, we explore the phosphatidylinositol-5-phosphate 4-kinases (PI5P4K), a family of lipid kinases that regulate pools of intracellular PI, and demonstrate that the PI5P4Kα isoform influences androgen receptor (AR) signaling, which supports prostate cancer (PCa) cell survival. The regulation of PI becomes increasingly important in the setting of metabolic stress adaptation of PCa during androgen deprivation (AD), as we show that AD influences PI abundance and enhances intracellular pools of PI-4,5-P2. We suggest that this PI5P4Kα-AR relationship is mitigated through mTORC1 dysregulation and show that PI5P4Kα colocalizes to the lysosome, the intracellular site of mTORC1 complex activation. Notably, this relationship becomes prominent in mouse prostate tissue following surgical castration. Finally, multiple PCa cell models demonstrate marked survival vulnerability following stable PI5P4Kα inhibition. These results nominate PI5P4Kα as a target to disrupt PCa metabolic adaptation to castrate resistance.

Sonicated Extract from the Aril of Momordica Cochinchinensis Inhibits Cell Proliferation and Migration in Aggressive Prostate Cancer Cells.

Momordica cochinchinensis or gac fruit has been reported to have several biological activities, including antioxidation, anti-inflammatory, and anticancer activities. However, the effect on cancer cell metastasis has not been extensively studied. With this aim, the extract from the aril part was selected and investigated for prostate cancer cell migration. The aril extracts were prepared as boiled extract, sonicated extract, ethanol extract, and HAE (hexane:acetone:ethanol; 2 : 1 : 1) extract, while the prostate cancer cell models were PC-3 and LNCaP cells. An MTT assay was performed to compare the antiproliferative effect between prostate cancer cells and normal Vero cells. As a result, the sonicated extract had the highest efficiency in PC-3 cells, with IC50 values of 2 mg/mL and 0.59 mg/mL for 48 and 72 h, respectively, while it had less of an effect in LNCaP cells and was not toxic to normal cells. Cell damage was further confirmed using LDH and cell cycle analysis. As a result, the sonicated extract did not cause cell damage or death and only inhibited cell proliferation. The effect on cancer metastasis was further examined by wound healing, transwell migration assays, and western blotting. The results demonstrated that the sonicated extract inhibited PC-3 cell migration and decreased MMP-9 but increased TIMP-1 expression. All these results support that gac fruit is a valuable source for further development as an anticancer agent for prostate cancer patients.