Sensitizes Prostate Cancer Cells Research Articles

CK2-dependent degradation of CBX3 dictates replication fork stalling and PARP inhibitor sensitivity.

DNA replication is a vulnerable cellular process, and its deregulation leads to genomic instability. Here, we demonstrate that chromobox protein homolog 3 (CBX3) binds replication protein A 32-kDa subunit (RPA2) and regulates RPA2 retention at stalled replication forks. CBX3 is recruited to stalled replication forks by RPA2 and inhibits ring finger and WD repeat domain 3 (RFWD3)-facilitated replication restart. Phosphorylation of CBX3 at serine-95 by casein kinase 2 (CK2) kinase augments cadherin 1 (CDH1)-mediated CBX3 degradation and RPA2 dynamics at stalled replication forks, which permits replication fork restart. Increased expression of CBX3 due to gene amplification or CK2 inhibitor treatment sensitizes prostate cancer cells to poly(ADP-ribose) polymerase (PARP) inhibitors while inducing replication stress and DNA damage. Our work reveals CBX3 as a key regulator of RPA2 function and DNA replication, suggesting that CBX3 could serve as an indicator for targeted therapy of cancer using PARP inhibitors.

Abstract 3294: The GSPT1 molecular glue degrader MRT-2359 is active against prostate cancer

Abstract We have previously described our GSPT1 molecular glue degrader MRT-2359, which was optimized to achieve preferential antiproliferative activity in non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) expressing high N-MYC or L-MYC mRNA. A clinical trial with this new drug candidate is ongoing (NCT05546268). Here, we present pre-clinical profiling of MRT-2359 across hundreds of cancer cell lines representing multiple cancer types, aiming at identifying other cancers where preferential sensitivity is associated with high expression of a MYC family member. These studies showed that prostate cancer cell lines clearly segregate into groups that are either sensitive or insensitive. Sensitive prostate cancer cell lines could be further divided into two subgroups: (1) androgen receptor positive cell lines displaying higher c-MYC mRNA expression levels than the other prostate cancer cell lines, (2) neuroendocrine prostate cancer cell lines with or without high N-MYC. The latter is in line with our previous observation that the neuroendocrine phenotype is generally associated with heightened sensitivity to MRT-2359 independently of MYC status. The insensitive cell lines were androgen receptor and neuroendocrine negative and displayed lower c-MYC mRNA levels. GSPT1 degradation in androgen receptor-positive cell lines led to rapid and deep loss of c-MYC protein as well as reduction of androgen receptor, including the splice variant AR-V7 that is associated with resistance to agents targeting androgen signaling. In androgen receptor-negative cell lines, the levels of c-MYC protein decreased only modestly upon GSPT1 degradation. Finally, in immunocompromised mice, xenografts of the AR-V7-positive cell line 22RV1 and the neuroendocrine prostate cell line NCI-H660, both of which are sensitive to MRT-2359 in vitro, were treated with several MRT-2359 dose regimens including continuous as well as intermittent (5 days on/9 days off) dosing. Most regimens led to marked tumor regression. Tumors of both models fully regressed after a 4-week course of 10 mg/kg MRT-2359 once daily, and no tumor regrowth could be detected after cessation of treatment. No significant in vivo response was observed for xenografts of the insensitive cell line PC-3. These data support the clinical investigation of MRT-2359 in prostate cancer. Citation Format: Ralph Tiedt, Martin Schillo, Arnaud Osmont, Débora Bonenfant, Rajiv Narayan, Owen Wallace, Markus Warmuth. The GSPT1 molecular glue degrader MRT-2359 is active against prostate cancer [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 3294.

Inhibition of Chk1 stimulates cytotoxic action of platinum-based drugs and TRAIL combination in human prostate cancer cells.

Checkpoint kinase 1 (Chk1) plays an important role in regulation of the cell cycle, DNA damage response and cell death, and represents an attractive target in anticancer therapy. Small-molecule inhibitors of Chk1 have been intensively investigated either as single agents or in combination with various chemotherapeutic drugs and they can enhance the chemosensitivity of numerous tumor types. Here we newly demonstrate that pharmacological inhibition of Chk1 using potent and selective inhibitor SCH900776, currently profiled in phase II clinical trials, significantly enhances cytotoxic effects of the combination of platinum-based drugs (cisplatin or LA-12) and TRAIL (tumor necrosis factor-related apoptosis inducing ligand) in human prostate cancer cells. The specific role of Chk1 in the drug combination-induced cytotoxicity was confirmed by siRNA-mediated silencing of this kinase. Using RNAi-based methods we also showed the importance of Bak-dependent mitochondrial apoptotic pathway in the combined anticancer action of SCH900776, cisplatin and TRAIL. The triple drug combination-induced cytotoxicity was partially enhanced by siRNA-mediated Mcl-1 silencing. Our findings suggest that targeting Chk1 may be used as an efficient strategy for sensitization of prostate cancer cells to killing action of platinum-based chemotherapeutic drugs and TRAIL.

2,4-dinitrophenol enhances cisplatin and etoposide cytotoxic activity on prostate cancer cell line.

Including additional compounds that disturb the energy metabolism of cancer cells in advanced cancer therapy regimens may be an approach to overcome the problem of drug resistance and the therapeutic effectiveness of classic chemotherapeutics. One of the compounds that decouple oxidative phosphorylation, and thus alter the activity of energy-producing pathways, is 2,4-DNP (2,4- dinitrophenol). The aim of the study was to assess the ability of the 2,4-DNP to sensitize prostate cancer cells to the action of cisplatin and etoposide, or to intensify their action. The research was carried out on three prostate cancer cell lines (LNCaP, PC-3, DU-145. To assess the effect of cisplatin or etoposide with 2,4-DNP on prostate cancer cells, MTT assay, analysis of the cell cycle and apoptosis detection was performed. Oxidative stress was investigated by CellRox fluorescence staining and expression of genes related to antioxidant defence. In addition, analysis was conducted of the expression of genes related to cell cycle inhibition, transporters associated with multi-drug resistance and DNA repair. The study showed that the simultaneous incubation of 2,4-DNP with cisplatin or etoposide enhances the cytotoxic effect of the chemotherapeutic agent only in LNCaP cells (oxidative phenotype). The enhanced cytotoxic effect of chemotherapeutics by 2,4-DNP may be the result of disturbed redox balance, reduced ability of cells to repair DNA, and the oxidative metabolic phenotype of prostate cancer cells.

The key cellular senescence related molecule RRM2 regulates prostate cancer progression and resistance to docetaxel treatment

BackgroundProstate cancer is a leading cause of cancer-related deaths among men worldwide. Docetaxel chemotherapy has proven effective in improving overall survival in patients with castration-resistant prostate cancer (CRPC), but drug resistance remains a considerable clinical challenge.MethodsWe explored the role of Ribonucleotide reductase subunit M2 (RRM2), a gene associated with senescence, in the sensitivity of prostate cancer to docetaxel. We evaluated the RRM2 expression, docetaxel resistance, and ANXA1 expression in prostate cancer cell lines and tumour xenografts models. In addition, We assessed the impact of RRM2 knockdown, ANXA1 over-expression, and PI3K/AKT pathway inhibition on the sensitivity of prostate cancer cells to docetaxel. Furthermore, we assessed the sensitivity of prostate cancer cells to the combination treatment of COH29 and docetaxel.ResultsOur results demonstrated a positive association between RRM2 expression and docetaxel resistance in prostate cancer cell lines and tumor xenograft models. Knockdown of RRM2 increased the sensitivity of prostate cancer cells to docetaxel, suggesting its role in mediating resistance. Furthermore, we observed that RRM2 stabilizes the expression of ANXA1, which in turn activates the PI3K/AKT pathway and contributes to docetaxel resistance. Importantly, we found that the combination treatment of COH29 and docetaxel resulted in a synergistic effect, further augmenting the sensitivity of prostate cancer cells to docetaxel.ConclusionOur findings suggest that RRM2 regulates docetaxel resistance in prostate cancer by stabilizing ANXA1-mediated activation of the PI3K/AKT pathway. Targeting RRM2 or ANXA1 may offer a promising therapeutic strategy to overcome docetaxel resistance in prostate cancer.Graphical

The effect of Ganoderma lucidum polysaccharide extract on sensitizing prostate cancer cells to flutamide and docetaxel: an in vitro study

Ganoderma lucidum polysaccharide is the most widely used complementary therapy in cancer. The present study aims to investigate the possible interaction between Ganoderma lucidum polysaccharide and Docetaxel (a chemotherapy drug) and the first-line medication for prostate cancer treatment (Flutamide) and sensitizing the cells to these treatments. The cytotoxic effects of Ganoderma lucidum polysaccharide in combination with Docetaxel and Flutamide on prostate cancer cells were investigated by the MTT test, Hoechst staining, and flow cytometry. In addition, the expression of genes related to apoptosis, angiogenesis, Epithelial-Mesenchymal Transition pathway (EMT), and prostate cancer biomarkers by Real-Time PCR was investigated. The results demonstrated that IC50 values for Ganoderma lucidum polysaccharide (30 μM and 20 μM), Docetaxel (10 μM and 5 μM), and Flutamide (20 μM and 12 μM) with MTT were confirmed by flow cytometry in a dose and time-dependent manner. Regarding the high efficacy of Ganoderma lucidum polysaccharide in combination with Flutamide and Docetaxel, 10 μM and 5 μM Flutamide were used instead of 20 μM and 12 μM and 5 μM and 2 μM Docetaxel was used instead of 10 μM and 5 μM in PC3 and LNCap, respectively. Moreover, for the first time, it was shown that Ganoderma lucidum polysaccharide alone and in combination with Docetaxel and Flutamide significantly augmented apoptosis, reduced cell migration and colonization, and downregulated expression of KLK2 and EMT pathway genes in both PC3 and LNCap cell line (P < 0.01). Ganoderma lucidum polysaccharide synergistically increased the effect of Docetaxel and Flutamide and increased the sensitivity of the prostate cancer cell lines to these drugs. Therefore, it may provide a new therapeutic strategy against prostate cancer.

Assessing the Potential of Small Peptides for Altering Expression Levels of the Iron-Regulatory Genes FTH1 and TFRC and Enhancing Androgen Receptor Inhibitor Activity in In Vitro Prostate Cancer Models.

Recent research highlights the key role of iron dyshomeostasis in the pathogenesis of prostate cancer (PCa). PCa cells are heavily dependent on bioavailable iron, which frequently results in the reprogramming of iron uptake and storage pathways. Although advanced-stage PCa is currently incurable, bioactive peptides capable of modulating key iron-regulatory genes may constitute a means of exploiting a metabolic adaptation necessary for tumor growth. Recent annual increases in PCa incidence have been reported, highlighting the urgent need for novel treatments. We examined the ability of LNCaP, PC3, VCaP, and VCaP-EnzR cells to form colonies in the presence of androgen receptor inhibitors (ARI) and a series of iron-gene modulating oligopeptides (FT-001-FT-008). The viability of colonies following treatment was determined with clonogenic assays, and the expression levels of FTH1 (ferritin heavy chain 1) and TFRC (transferrin receptor) were determined with quantitative polymerase chain reaction (PCR). Peptides and ARIs combined significantly reduced PCa cell growth across all phenotypes, of which two peptides were the most effective. Colony growth suppression generally correlated with the magnitude of concurrent increases in FTH1 and decreases in TFRC expression for all cells. The results of this study provide preliminary insight into a novel approach at targeting iron dysmetabolism and sensitizing PCa cells to established cancer treatments.

Loss of PDE4D7 expression promotes androgen independence, neuroendocrine differentiation and alterations in DNA repair: implications for therapeutic strategies

BackgroundAndrogen signalling remains the seminal therapeutic approach for the management of advanced prostate cancer. However, most tumours eventually shift towards an aggressive phenotype, characterised by androgen independence and treatment resistance. The cyclic adenosine monophosphate (cAMP) pathway plays a crucial role in regulating various cellular processes, with the phosphodiesterase PDE4D7 being a vital modulator of cAMP signalling in prostate cancer cells.MethodsUsing shRNA-mediated PDE4D7 knockdown in LNCaP cells and downstream analysis via RNA sequencing and phenotypic assays, we replicate clinical observations that diminished PDE4D7 expression promotes an aggressive prostate cancer phenotype.ResultsOur study provides evidence that loss of PDE4D7 expression represents a pivotal switch driving the transition from an androgen-sensitive state to hormone unresponsiveness and neuroendocrine differentiation. In addition, we demonstrate that PDE4D7 loss affects DNA repair pathways, conferring resistance to poly ADP ribose polymerase (PARP) inhibitors.ConclusionReinstating PDE4D7 expression sensitises prostate cancer cells to anti-androgens, DNA damage response inhibitors, and cytotoxic therapies. These findings provide significant insight into the regulatory role of PDE4D7 in the development of lethal prostate cancer and the potential of its modulation as a novel therapeutic strategy.

Comparative proteome and serum analysis identified FSCN1 as a marker of abiraterone resistance in castration-resistant prostate cancer.

Abiraterone (Abi) is an androgen receptor signaling inhibitor that significantly improves patients' life expectancy in metastatic prostate cancer (PCa). Despite its beneficial effects, many patients have baseline or acquired resistance against Abi. The aim of this study was to identify predictive serum biomarkers for Abi treatment. We performed a comparative proteome analysis on three Abi sensitive (LNCaPabl, LAPC4, DuCaP) and resistant (LNCaPabl-Abi, LAPC4-Abi, DuCaP-Abi) PCa cell lines using liquid chromatography tandem mass spectrometry (LC-MS/MS) technique. Two bioinformatic selection workflows were applied to select the most promising candidate serum markers. Serum levels of selected proteins were assessed in samples of 100 Abi-treated patients with metastatic castration-resistant disease (mCRPC) using ELISA. Moreover, FSCN1 serum concentrations were measured in samples of 69 Docetaxel (Doc) treated mCRPC patients. Our proteome analysis identified 68 significantly, at least two-fold upregulated proteins in Abi resistant cells. Using two filtering workflows four proteins (AMACR, KLK2, FSCN1 and CTAG1A) were selected for ELISA analyses. We found high baseline FSCN1 serum levels to be significantly associated with poor survival in Abi-treated mCRPC patients. Moreover, the multivariable analysis revealed that higher ECOG status (>1) and high baseline FSCN1 serum levels (>10.22 ng/ml by ROC cut-off) were independently associated with worse survival in Abi-treated patients (p < 0.001 and p = 0.021, respectively). In contrast, no association was found between serum FSCN1 concentrations and overall survival in Doc-treated patients. Our analysis identified baseline FSCN1 serum levels to be independently associated with poor survival of Abi-treated, but not Doc-treated mCRPC patients, suggesting a therapy specific prognostic value for FSCN1.

AR activates YAP/TAZ differentially in prostate cancer.

The Hippo signalling pathway is a master regulator of cell growth, proliferation, and cancer. The transcriptional coregulators of the Hippo pathway, YAP and TAZ, are central in various cancers. However, how YAP and TAZ get activated in most types of cancers is not well understood. Here, we show that androgens activate YAP/TAZ via the androgen receptor (AR) in prostate cancer (PCa), and that this activation is differential. AR regulates YAP translation while inducing transcription of the TAZ encoding gene, WWTR1 Furthermore, we show that AR-mediated YAP/TAZ activation is regulated by the RhoA GTPases transcriptional mediator, serum response factor (SRF). Importantly, in prostate cancer patients, SRF expression positively correlates with TAZ and the YAP/TAZ target genes CYR61 and CTGF We demonstrate that YAP/TAZ are not essential for sustaining AR activity, however, targeting YAP/TAZ or SRF sensitize PCa cells to AR inhibition in anchorage-independent growth conditions. Our findings dissect the cellular roles of YAP, TAZ, and SRF in prostate cancer cells. Our data emphasize the interplay between these transcriptional regulators and their roles in prostate tumorigenesis and highlight how these insights might be exploited therapeutically.

Androgen receptor knockdown enhances prostate cancer chemosensitivity by down-regulating FEN1 through the ERK/ELK1 signalling pathway.

Flap endonuclease 1 (FEN1) is highly upregulated in prostate cancer and promotes the growth of prostate cancer cells. Androgen receptor (AR) is the most critical determinant of the occurrence, progression, metastasis, and treatment of prostate cancer. However, the effect of FEN1 on docetaxel (DTX) sensitivity and the regulatory mechanisms of AR on FEN1 expression in prostate cancer need to be further studied. Bioinformatics analyses were performed using data from the Cancer Genome Atlas and the Gene Expression Omnibus. Prostate cancer cell lines 22Rv1 and LNCaP were used. FEN1 siRNA, FEN1 overexpression plasmid, and AR siRNA were transfected into cells. Biomarker expression was evaluated by immunohistochemistry and Western blotting. Apoptosis and the cell cycle were explored using flow cytometry analysis. Luciferase reporter assay was performed to verify the target relationship. Xenograft assays were conducted using 22Rv1 cells to evaluate the in vivo conclusions. Overexpression of FEN1 inhibited cell apoptosis and cell cycle arrest in the S phase induced by DTX. AR knockdown enhanced DTX-induced cell apoptosis and cell cycle arrest at the S phase in prostate cancer cells, which was attenuated by FEN1 overexpression. In vivo experiments showed that overexpression of FEN1 significantly increased tumour growth and weakened the inhibitory effect of DTX on prostate tumour growth, while AR knockdown enhance the sensitivity of DTX to prostate tumour. AR knockdown resulted in FEN1, pho-ERK1/2, and pho-ELK1 downregulation, and the luciferase reporter assay confirmed that ELK1 can regulate the transcription of FEN1. Collectively, our studies demonstrate that AR knockdown improves the DTX sensitivity of prostate cancer cells by downregulating FEN1 through the ERK/ELK1 signalling pathway.

Abstract A002: A reciprocal signaling crosstalk between the AR and BCl2-AKT pathways induces castration resistance in castration sensitive prostate cancer

Abstract Introduction: A leading contributor to the significant mortality burden of prostate cancer (PC) is the resistance to androgen deprivation therapy (ADT). Although most PCs are initially sensitive to ADT, the duration of response is variable, and relapse invariably occurs in the transition to metastatic castration-resistant prostate cancer (mCRPC), the lethal form of the disease. Therefore, it is essential to discover and validate early resistance mechanisms that initially protect castration sensitive prostate cancer (CSPC) cells from ADT and to develop novel combination therapies that can block or delay the ADT-induced shift from CSPC to mCRPC. Overexpression of the hallmark antiapoptotic gene B-cell lymphoma 2 (BCL2) is a potential mechanism of resistance to ADT. Methods: To discover the molecular drivers of castration resistance, we analyzed the tumor transcriptomic profile of a cohort of localized PC patients (N=58) treated with neoadjuvant-intensive ADT (NCT00924469; Taplin et al, 2014, Sowalsky et al, 2018). Experimentally, we treated CSPC cells and genetically engineered mice (GEM) prostate tumors with ADT and analyzed the signaling pathways, which were enriched post-ADT treatment compared untreated samples. Results: We discovered ~10-fold increased mRNA expression of BCL2 (p&amp;lt;0.001) in ADT-treated localized PC patients compared to untreated (standard of care surgery) patients in NCT00924469 samples. Our experimental study showed that treatment with AR inhibitors strongly augments BCL2 expression in human CSPC cell lines and GEM PC model, indicating possible direct negative regulation of BCL2 by the AR-signaling pathway. Mechanistically, our preliminary data reveal a striking induction of cell metabolism pathways (fatty acid and xenobiotic metabolism), including activation of PI3K/AKT signaling in BCL2-overexpressing CSPC cells. We used siRNA-mediated BCL2 knockdown in LNCaP cells and showed that loss of BCL2 strongly suppressed ADT-induced AKT- phosphorylation. We also showed increased Bcl2 mRNA expression in PTEN-knockout mice-derived prostate organoids compared to the wild-type control. Furthermore, we observed that AKT kinase -inhibitor MK2206 strongly inhibits enzalutamide-induced BCL2 expression in LNCaP cells. Conclusion: Together our data indicate a non-canonical role of BCL2 in activating PI3K/AKT signaling in prostate cancer. For the first time, we demonstrate the crucial importance of AR-BCL2-AKT signaling pathway crosstalk in CSPC biology and reveal this complex signaling crosstalk may act as a key driver of CSPC transformation to lethal CRPC. Citation Format: Goutam Chakraborty, Rahim Hirani, Subhiksha Nandakumar, Nabila Zaman, Teja Muralidhar Kalidindi, Sai Harisha Rajanala, Gwo-Shu M. Lee, Konrad H. Stopsack, Naga Vara Kishore Pillarsetty, Lorelei A. Mucci, Daniel C. Danila, Philip W. Kantoff. A reciprocal signaling crosstalk between the AR and BCl2-AKT pathways induces castration resistance in castration sensitive 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 A002.

Abstract B022: Dopamine receptor antagonists sensitize prostate cancer cells to androgen targeted therapy

Abstract Prostate cancer (PC) incidence is predicted to reach around 2 million new cases by 2040. High fat diet and obesity are associated with the progression and mortality of PC. Palmitate is a common saturated fatty acid, it induces endoplasmic reticulum (ER) stress that activates the unfolded protein response (UPR). Failure to adapt to ER stress results in apoptosis to eliminate irreversibly damaged cells. Master regulator analysis found that Arid5a was a master regulator of saturated fat-induced cellular responses. We confirmed that exogenous palmitate activated ARID5a/UPR signaling, while further activation could induce apoptosis. In trying to determine the mechanism of ARID5a activation, we found that palmitate promoted the expression of dopamine receptors 2 and 3 (DRD2, DRD3) in prostate cancer cell lines. Since high diets have other deleterious effects, we tested the role of dopamine receptor antagonists (e.g. ONC201, prochlorperazine) and found them to serve as UPR activators, inducing apoptosis in ARCaPM and 22Rv1 cells. As our data showed that ARID5a expression could inhibit prostate-specific membrane antigen (PSMA), we next tested the role of dopamine receptor antagonists in sensitizing castrate resistant cells to androgen targeted therapy. Both castrate resistant cell lines (22Rv1 and ARCaPM) were found to be made sensitive to enzalutamide by dopamine inhibition, inhibiting cell proliferation and promoting apoptosis. These findings are especially compelling since dopamine receptor antagonist, prochlorperazine, is a commonly prescribed anti-nausea drug and ONC201 is currently in clinical trials meeting safety endpoints. Preclinical studies in mouse models of castrate resistant PC support the administration of such dopamine receptor antagonists with androgen targeted therapy to sensitize otherwise refractile tumors by the promotion of ER stress pathway, addressing a common adaptation mechanism employed by cancer cells. Citation Format: Le Zhang, Sandrine Billet, Gabrielle Gonzales, Krizia Rohena-Rivera, Hayato Muranaka, Yeonjoo Lee, Sungyong You, Edwin M. Posadas, Neil A. Bhowmick. Dopamine receptor antagonists sensitize prostate cancer cells to androgen targeted therapy [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 B022.

Cysteine depletion sensitizes prostate cancer cells to agents that enhance DNA damage and to immune checkpoint inhibition

BackgroundProstate Cancer (PCa) represents one of the most commonly diagnosed neoplasms in men and is associated with significant morbidity and mortality. Therapy resistance and significant side effects of current treatment strategies indicate the need for more effective agents to treat both androgen-dependent and androgen-independent PCa. In earlier studies, we demonstrated that depletion of L-cysteine/cystine with an engineered human enzyme, Cyst(e)inase, increased intracellular ROS levels and inhibited PCa growth in vitro and in vivo. The current study was conducted to further explore the mechanisms and potential combinatorial approaches with Cyst(e)inase for treatment of PCa.MethodsDNA single strand breaks and clustered oxidative DNA damage were evaluated by alkaline comet assay and pulsed field gel electrophoresis, respectively. Neutral comet assay and immunofluorescence staining was used to measure DNA double strand breaks. Cell survival and reactive oxygen species level were measured by crystal violet assay and DCFDA staining, respectively. Western blot was used to determine protein expression. FACS analyses were preformed for immune cell phenotyping. Allograft and xenograft tumor models were used for assessing effects on tumor growth.ResultsPCa cells treated with Cyst(e)inase lead to DNA single and double strand breaks resulted from clustered oxidative DNA damage (SSBs and DSBs). Cyst(e)inase in combination with Auranofin, a thioredoxin reductase inhibitor, further increased intracellular ROS and DNA DSBs and synergistically inhibited PCa cell growth in vitro and in vivo. A combination of Cyst(e)inase with a PARP inhibitor (Olaparib) also increased DNA DSBs and synergistically inhibited PCa cell growth in vitro and in vivo without additional ROS induction. Knockdown of BRCA2 in PCa cells increased DSBs and enhanced sensitivity to Cyst(e)inase. Finally, Cyst(e)inase treatment altered tumor immune infiltrates and PD-L1 expression and sensitized PCa cells to anti-PD-L1 treatment.ConclusionsThe current results demonstrate the importance of oxidative DNA damage either alone or in combination for Cyst(e)inase-induced anticancer activity. Furthermore, cysteine/cystine depletion alters the tumor immune landscape favoring enhanced immune checkpoint inhibition targeting PD-L1. Thus, combinatorial approaches with Cyst(e)inase could lead to novel therapeutic strategies for PCa.

OC-0430 Class I histone deacetylase inhibitor Entinostat sensitises prostate cancer cells to radiation

OC-0430 Class I histone deacetylase inhibitor Entinostat sensitises prostate cancer cells to radiation

Chronic exposure to nitric oxide sensitizes prostate cancer cells and improved ZnO/CisPt NPs cytotoxicity and selectivity

The co-therapy of common chemotherapeutics with nitric oxide (NO), an endogenous signaling molecule, is proposed as an alternative to sensitize cancer cells and enhance treatments’ efficacy. Herein, we have synthesized cisplatin-releasing zinc oxide nanoparticles (ZnO/CisPt NPs), which promoted a sustained and pH targeted release, able to release a higher amount of CisPt at tumor microenvironment conditions. This material was combined with a chronic NO treatment, at low concentration, in prostate cancer cells (PC3). NO treatment enhanced the S-NO concentration in PC3 cells, suggesting the nitrosylation or transnitrosylation processes enhancement, which are directly related to S-NO binding to proteins, function alterations and cancer cells death. Indeed, these mechanisms directly impacted the cytotoxic effect of ZnO/CisPt NPs, inducing a 30 % higher viability reduction of PC3 cells after NO treatment, along with a higher selectivity index when compared to normal human fibroblasts (FN1).

Abstract 1723: Ferroptosis is a novel therapeutic target for RB1 deficient lethal prostate cancer

Abstract Background: Although the development of next-generation antiandrogens has significantly extended the survival time of patients with metastatic castration-resistant prostate cancer (mCRPC), drug resistance inevitably developed over time. Therefore, the identification of novel therapeutic strategies targeting mCRPC is urgent. RB1 deficiency is a common genetic event and contributes to the development of therapy resistance and poor prognosis in prostate cancer. However, effective therapies against RB1-deficient lethal prostate cancer remain elusive. Here we determined how RB1 regulates the sensitivity of prostate cancer cells to ferroptosis, a form of regulated cell death driven by iron-dependent lipid peroxidation, and whether we can exploit ferroptosis for the treatment of RB1 deficient lethal prostate cancer. Methods: To determine how RB1 regulates ferroptosis in prostate cancer, we generated RB1 stable knockdown prostate cancer cell lines using lentivirus-delivered shRNAs. We compared cellular sensitivity to ferroptosis and associated lipid peroxidation between control and RB1 stable knockdown prostate cancer cells. Using western blotting, qPCR, and ChIP analyses, we examined the regulation of ferroptosis by RB1. We also evaluated the therapeutic efficacy of ferroptosis inducers in cell-derived xenograft, patient-derived xenograft, and genetically engineered mouse models. Results: Our studies revealed that RB1 deficiency sensitizes prostate cancer cells to ferroptosis. Mechanistically, we found that the E2F family of transcription factors directly binds and activates the ACSL4 promoter and that RB1 inhibits ferroptosis by suppressing E2F-mediated ACSL4 transcriptional activation. More importantly, our preclinical studies demonstrated that induction of ferroptosis by JKE-1674, a recently discovered ferroptosis inducer, significantly blocks RB1 deficient prostate tumor growth and metastasis, and improves the overall survival of mice in the absence of obvious toxicity. Conclusions: Our findings uncover an RB1/E2F/ACSL4 molecular axis that governs ferroptosis and also suggest a new approach to the treatment of RB1-deficient lethal prostate cancer. Citation Format: Mu-En Wang, Jiaqi Chen, Yi Lu, Jinjin Wy, Jianhong Ou, John Asara, Andrew Armstrong, Qianben Wang, Lei Li, Yuzhuo Wang, Jiaoti Huang, Ming Chen. Ferroptosis is a novel therapeutic target for RB1 deficient lethal prostate cancer [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 1723.

Abstract 2475: Bromodomain inhibitor: MT1 and its potential role in modulation of prostate cancer progression

Abstract Bromodomains (BD) are epigenetic readers of histone acetylation involved in chromatin remodeling and transcriptional regulation of protooncogene cellular myelocytomatosis (c- Myc) and other genes. Because c-Myc cannot be directly targeted by small molecular inhibitors due to disordered alpha helical structure, epigenetic targeting of c-Myc by BD inhibitors is an attractive therapeutic strategy for diseases such as prostate cancer (PC) associated with increased c-Myc upregulation with advancing disease. We studied the efficacy of MT1, a novel bivalent BD inhibitor that is 100-fold more potent than the first in class BD inhibitor JQ1, at inhibiting PC growth. We tested the effect on viability by MT-1 on PC cell lines, 3D spheroids derived from clinically annotated drug resistant patient derived xenografts (PDX), mice PDX models and corroborated the molecular mechanism of MT1 down regulation of Myc leading to downstream Myc-dependent up regulation of Protein Kinase D1 (PrKD) substrate phosphorylation by western blot. MT-1 inhibited growth of PC in castration sensitive (LNCaP) and resistant PC cells (PC-3). MT-1 treatment upregulated PrKD expression and phosphorylation of known PrKD substrates: threonine 120 (Thr-120) residues in beta-catenin and the serine 216 in Cell Division Cycle 25 (CDC25C) in PC-3 cells. Moreover, MT-1 was effective in inhibition of 3D spheroids growth at IC 50 between 0.27-0.92µM in Abiraterone, Enzalutamide, Docetaxel, Cabazitaxel metastatic castrate resistant PCa patient-derived tumor 3D spheroids. Additionally, MT1 was effective in inhibiting the tumor growth in PDX mice model. A combined intra-peritoneal administration of MT-1 with another c-Myc inhibitor (3JC48-3), an obligate c-Myc and MYC-associated protein X (MAX) heterodimerization inhibitor, increased the efficacy of inhibiting the PDX growth in mice. This study provides strong pre-clinical in vitro and in vivo evidence for advancing MT- 1 as a novel c-Myc targeting drug in PC. The MT-1 drug development will likely be highly impactful as c-Myc is dysregulated in three fourths of men with advanced PC. Citation Format: Sanjeev Shukla, Mohammed Al-Toubat, Allison H. Feibus, Ahmed Elshafei, Carlos Riveros, Nathalie Meurice, Justyna Gleba, Jonathan Chardon-Robles, Adam M. Kase, John A. Copland III, Joachim L. Petit, Teruko Osumi, K.C. Balaji. Bromodomain inhibitor: MT1 and its potential role in modulation of 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 2475.

Abstract 4816: Targeting GCN2 regulation of amino acid homeostasis sensitizes prostate cancer cells to senolytic therapies

Abstract The integrated stress response (ISR) features a family of eIF2 kinases that sense cellular stress, triggering translational and transcriptional modes of gene expression that enhance cell adaptation to the underlying stress. Previously we reported (Cordova et al., 2022 eLife) that prostate cancer (PCa) cells rely on one of these eIF2 kinases, GCN2, for maintenance of amino acid homeostasis and sustained proliferation. GCN2 functions to enhance expression of amino acid transporters and subsequent import of essential amino acids (EAAs) that are necessary to sustain PCa growth. Genetic loss or pharmacological inhibition of GCN2 results in decreased expression of amino acid transporters, severe depletion of intracellular EAAs, and decreased proliferation of PCa cells in culture and mouse xenograft models. Although loss of GCN2 in PCa cells reduces proliferation, depletion of this eIF2 kinase is suggested to lead to cell stasis and modest cell death. We hypothesize that the static phenotype by GCN2 inhibition in PCa cells renders these cells vulnerable to senolytic treatment and is a potential therapeutic target in combination therapies. To address this idea, we utilized models of androgen-sensitive and castration-resistant PCa and non-tumorigenic prostate epithelial cells. GCN2 inhibition induced a static phenotype in PCa cell lines, but not non-tumorigenic prostate epithelial cells, and this was accompanied by increased expression of the senescent markers p53, p21, p27, and MCL-1. Furthermore, induction of senescent markers following GCN2 inhibition in PCa cells was reversed by supplementation with EAAs, suggesting that limitation of EAAs is critical to the induction of cell stasis. Of importance, treatment of PCa cells with Navitoclax, a senolytic agent that targets Bcl-2 family of anti-apoptotic proteins, in combination with GCN2 inhibition resulted in enhanced cell death and apoptosis compared to each single treatment alone. Our results suggest that GCN2 inhibition in PCa cells leads to depletion of EAAs and induction of a static phenotype, rendering these cells vulnerable to targeting the Bcl-2 family of proteins to expedite cell death. As such, therapies integrating GCN2 inhibition and senolytic agents are proposed to be effective strategies for treatment of PCa. Citation Format: Noah R. Sommers, Ricardo A. Cordova, Angela J. Klunk, Roberto Pili, Ronald C. Wek, Kirk A. Staschke. Targeting GCN2 regulation of amino acid homeostasis sensitizes prostate cancer cells to senolytic therapies. [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 4816.

PD04-07 THE BIVALENT BROMODOMAIN INHIBITOR; MT-1 INHIBITS PROSTATE CANCER GROWTH

You have accessJournal of UrologyCME1 Apr 2023PD04-07 THE BIVALENT BROMODOMAIN INHIBITOR; MT-1 INHIBITS PROSTATE CANCER GROWTH Sanjeev Shukla, Mohammed Al-Toubat, Carlos Riveros, Allison H. Feibus, Ahmed El-shafie, Adam M. Kase, John A. Copland, Joachim L. Petit, Nathalie Meurice, Justyna Gleba, Jonathan Chardon-Robles, Teruko Osumi, and K. C. Balaji Sanjeev ShuklaSanjeev Shukla More articles by this author , Mohammed Al-ToubatMohammed Al-Toubat More articles by this author , Carlos RiverosCarlos Riveros More articles by this author , Allison H. FeibusAllison H. Feibus More articles by this author , Ahmed El-shafieAhmed El-shafie More articles by this author , Adam M. KaseAdam M. Kase More articles by this author , John A. CoplandJohn A. Copland More articles by this author , Joachim L. PetitJoachim L. Petit More articles by this author , Nathalie MeuriceNathalie Meurice More articles by this author , Justyna GlebaJustyna Gleba More articles by this author , Jonathan Chardon-RoblesJonathan Chardon-Robles More articles by this author , Teruko OsumiTeruko Osumi More articles by this author , and K. C. BalajiK. C. Balaji More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003228.07AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Bromodomains (BD) are epigenetic readers of histone acetylation involved in chromatin remodeling and transcriptional regulation of protooncogene cellular myelocytomatosis (c-Myc) and other genes. Because c-Myc cannot be directly targeted by small molecular inhibitors due to disordered alpha helical structure, epigenetic targeting of c-Myc by BD inhibitors is an attractive therapeutic strategy for advanced prostate cancer (PC) associated with increased c-Myc upregulation . We studied the efficacy of MT1, a novel bivalent BD inhibitor that is 100-fold more potent than the first in class BD inhibitor JQ1, at inhibiting PC growth METHODS: We tested the effect on viability by MT-1 on PC cell lines, 3D spheroids derived from clinically annotated drug resistant patient derived xenografts (PDX), mice PDX models and corroborated the molecular mechanism of MT1 down regulation of Myc leading to downstream Myc-dependent up regulation of Protein Kinase D1 (PrKD) substrate phosphorylation by western blot. RESULTS: MT-1 inhibited growth of PC in castration sensitive (LNCaP) and resistant PC cells (PC-3). MT-1 treatment upregulated PrKD expression and phosphorylation of known PrKD substrates: threonine 120 (Thr-120) residues in beta-catenin and the serine 216 in Cell Division Cycle 25 (CDC25C) in PC-3 cells. Moreover, MT-1 was effective in inhibition of 3D spheroids growth at IC50 between 0.27-0.92µM in Abiraterone, Enzalutamide, Docetaxel, Cabazitaxel metastatic castrate resistant PCa patient-derived tumor 3D spheroids. Additionally, MT1 was effective in inhibiting the tumor growth in PDX mice model. A combined intra-peritoneal administration of MT-1 with another c-Myc inhibitor (3JC48-3), an obligate c-Myc and MYC-associated protein X (MAX) heterodimerization inhibitor, increased the efficacy of inhibiting the PDX growth in mice. CONCLUSIONS: This study provides strong pre-clinical in vitro and in vivo evidence for advancing MT-1 as a novel c-Myc targeting drug in PC. The MT-1 drug development will likely be highly impactful as c-Myc is dysregulated in three fourths of men with advanced PC. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e144 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Sanjeev Shukla More articles by this author Mohammed Al-Toubat More articles by this author Carlos Riveros More articles by this author Allison H. Feibus More articles by this author Ahmed El-shafie More articles by this author Adam M. Kase More articles by this author John A. Copland More articles by this author Joachim L. Petit More articles by this author Nathalie Meurice More articles by this author Justyna Gleba More articles by this author Jonathan Chardon-Robles More articles by this author Teruko Osumi More articles by this author K. C. Balaji More articles by this author Expand All Advertisement PDF downloadLoading ...