Enzalutamide-resistant Cells Research Articles

Abstract 5679: Androgen receptor degraders overcome common resistance mechanisms developed during prostate cancer treatment

Abstract Background: Androgen receptor (AR) signaling is critical for prostate development and homeostasis as well as for the initiation and progression of prostate cancer (PCa). Indeed, the clinical development of second-generation AR antagonists, including enzalutamide, has confirmed that AR remains a key oncogene in castration-resistant prostate cancer (CRPC). Furthermore, response to enzalutamide is temporary and incremental, and PCa cells that develop resistance to AR-targeted therapy usually maintain AR expression. Therefore, with the hypothesis that AR protein is still active even during castration- and enzalutamide-resistant states, we employed the proteolysis targeting chimera (PROTAC) strategy to build compounds that targeted the AR through proteasomal degradation. We developed an optimized functional molecule, ARD-61, that targets enzalutamide-resistant and AR splice variant (including AR-V7, which lacks the ligand binding domain) overexpressing cells in vitro and in vivo. Methods/Results: To characterize ARD-61, we performed western blotting, qRT-PCR, growth assays, xenograft studies, as well as proteomic and RNA-sequencing analyses. Additionally, to investigate the sensitivity of AR splice variants to ARD-61, we created CRISPR-Cas9 mediated stable AR-V7 overexpression in LNCaP cells. ARD-61 functions to rapidly and specifically degrade AR protein, and thus decreases downstream AR signaling in a wide variety (e.g. enzalutamide sensitive, AR-mutated, enzalutamide resistant) of AR-positive cell lines and tumor xenografts. Enzalutamide-sensitive and -resistant cell lines were similarly sensitive to ARD-61 in vivo and in vitro. CRISPR-induced endogenous overexpression of AR-V7 had no effect on the sensitivity of cells to ARD-61 or enzalutamide. Conclusions: Our data reveal the necessity of full-length AR in all Pca stages. Despite continued AR-antagonization, enzalutamide-resistant cell lines require full-length AR for sustained survival. Further, AR-variant overexpression, previously shown to promote resistance to AR-targeted therapies, still required AR protein with an intact ligand-binding domain to maintain growth in our models. Our data illustrate the importance of continued targeting of AR in advanced Pca, as well as demonstrate the efficacy of ARD-61. Ultimately, through its clinical translation, we anticipate the development of ARD-61 to be a therapeutic advance for patients with the metastatic CRPC. Citation Format: Steven Kregel, Chao Wang, Xin Han, Lanbo Xiao, Ester Fernandez-Salas, Pushpinder Bawa, Brooke L. McCollum, Kari Wilder-Romans, Ingrid J. Apel, Xuhong Cao, Corey Speers, Shaomeng Wang, Arul M. Chinnaiyan. Androgen receptor degraders overcome common resistance mechanisms developed during prostate cancer treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5679.

Abstract 1836: ONC201 shows synergistic effect with the androgen receptor AR-inhibitor darotulamide in prostate cancer models

Abstract Prostate cancer (PC) is the most frequently diagnosed cancer among men in the United States and is the 3rd cause of cancer mortality. Despite advances in the treatment and understanding of pathogenesis, patients with metastatic PC invariably progress to a lethal stage of castration-resistant prostate cancer (CRPC). Inhibition of androgen signaling remains crucial for the treatment of CRPC, but novel treatment strategies are urgently needed. ONC201 is a first-in-class, selective inhibitor of dopamine receptor D2 that upregulates death-receptor 5 and induces apoptosis. ONC201 induced apoptosis in PC cell lines and showed synergy with enzalutamide, docetaxel and everolimus (Lev A Mol Cancer Res 2018). Darolutamide (DARO) is a novel androgen receptor (AR) antagonist approved for treatment of patients with non-metastatic CRPC. DARO has higher affinity to AR and preclinical activity against enzalutamide-resistant PC cell lines including AR variants associated with enzalutamide agonism (Borgmann H Eur Urol 2018). We treated human PC cell lines (LNCAP [castration sensitive, AR wild-type], 22Rv1 [castration-resistant cell line that expresses AR splice variant AR-V7], DU145 [AR negative], PC3 [AR negative]) with DARO alone and combined with ONC201. Single-agent DARO decreased PC cell viability in Cell-Titer-Glo assays (IC50s of 10 and 693 nM for LNCAP and DU145, respectively). ONC201 showed strong synergism with DARO in LNCAP cells (combination indices < 1 at concentrations of 156, 312, 625 nM, and 1.25 µM of DARO with 2.5 μM ONC201). ONC201 induced robust apoptosis in 22Rv1 as measured by PARP cleavage, which was partially amplified by DARO. PARP cleavage was also observed in LNCAP cells with less intensity and not potentiated by DARO. ONC201 reduced the expression of phospho-AR (p-AR) in both 22Rv1 and LNCAP. The combination of ONC201 and DARO had a significant additive effect in reducing p-AR in 22Rv1, but not in LNCAP. ONC201 reduced PSA protein levels in LNCAP cells while DARO alone did not cause any significant change in PSA. Immunofluorescence experiments showed that DARO caused significant reduction of AR nuclear translocation in both 22rV1 and LNCAP cells. The combination with ONC201 potentiated this inhibition of AR translocation in both cell lines. ONC201 showed strong antiproliferative activity against PC cells lines independent of AR status. Combination of ONC201 with DARO demonstrated synergy in enzalutamide resistant 22Rv1 cells expressing AR-V7 with marked reduction of nuclear localization of AR. Our studies provide preclinical rationale for combination of ONC201 with DARO as a novel therapy of PC. Citation Format: Fabio Tavora, Lanlan Zhou, Ali Amin, Safran Howard, Navaraj Arunasalam, Andre de Souza, Anthony Mega, Dragan Golijanin, Wafik El-Deiry, Benedito Carneiro. ONC201 shows synergistic effect with the androgen receptor AR-inhibitor darotulamide in prostate cancer models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1836.

Abstract 2612: Neuropilin-2 promotes enzalutamide-resistant neuroendocrine prostate cancer

Abstract Background: Neuroendocrine prostate cancer (NEPC) is a lethal subtype of prostate cancer (PC) that emerges after androgen deprivation therapy in advanced PC patients, with incidence significantly increased in recent years due to the widespread use of highly potent antiandrogens such as enzalutamide (ENZ). This study investigated the role of neuropilin-2 (NRP2) in the development and progression of ENZ-induced NEPC. Methods: Human PC tissue microarrays with different characteristics, including hormone naïve, castration resistant (CR) and neuroendocrine (NE), were analyzed for NRP2 expression by immunohistochemistry. Human PC cells were manipulated for stable knockdown or overexpression of NRP2, and then subjected to cell proliferation, cell colony formation and tumorsphere formation assays, and Western blot/RT-qPCR examination of NE marker expression. Results: NRP2 expression was elevated in CRPC and NEPC patient samples compared to hormone-naïve counterparts, which was supported by association of higher NRP2 expression with hormone-refractory and NE status of PC from additional clinical data sets. Increased NRP2 expression was found in LNCaP cells treated with ENZ (10 µM, up to 7 days) as well as in the ENZ-resistant C4-2BENZR cells (with acquired resistance to ENZ at 20 µM). Both cell lines exhibited treatment-induced NEPC features, including NE differentiation cell morphology, AR suppression and NE marker induction. Silencing of NRP2 in C4-2BENZR and 22Rv1 (with inherent ENZ resistance and NE traits) cells decreased cell proliferation by 50% and 75% respectively, which was corroborated in colony formation and tumorsphere assays. Silencing of NRP2 also increased apoptosis in both cell lines. NRP2 silencing further led to reduced expression of NE markers, including CHGA, SYP, CD56 and SOX2. Conversely, enforced expression of NRP2 in LNCaP and 22Rv1 cells accelerated cell proliferation by up to 4-fold, which was paralleled by increased cell colony and tumorsphere formation, reduced cell apoptosis, upregulation of NE marker expression (CHGA, SYP, NSE, CD56 and SOX2), and downregulation of AR and AR target genes (PSA, TMPRSS2, FKBP5 and KLK2). Mechanistically, NRP2 induced phosphorylation of STAT3 in C4-2BENZR and 22Rv1 cells as revealed by phospho-kinase antibody arrays, which will be further investigated for downstream effectors mediating NRP2's function in NEPC. Conclusion: NRP2 contributes to PC disease progression towards a NE phenotype following ENZ treatment and subsequent emergence of ENZ resistance, which provides new insights into understanding the mechanism underlying development of antiandrogen-induced NEPC and developing a new target for treating this lethal disease. Citation Format: Jing Wang, Jingjing Li, Boyang Wu, Lijuan Yin. Neuropilin-2 promotes enzalutamide-resistant neuroendocrine prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2612.

Abstract 1467: Metabolic reprogramming fuels prostate cancer cells towards enzalutamide resistance

Abstract Androgen deprivation therapy is standard care for advanced-stage prostate cancer. Enzalutamide (Xtandi®), a second-generation antiandrogen is the most clinically prescribed drug that has prolonged survival in men. However, this response is temporary and results in the rapid emergence of resistance. The underlying mechanisms of enzalutamide resistance remain unclear. Emerging evidence suggests that metabolic reprogramming mediates resistance to standard-of-care therapies. To identify the molecular underpinnings of enzalutamide resistance, we performed Next-Gen Sequencing (NGS), analyzing global metabolic changes in enzalutamide-resistant clones utilizing two androgen-responsive human prostate cancer cells and comparing them with parental counterparts. Enzalutamide-resistant LNCaP and C4-2B cells were generated from 20µM enzalutamide exposed for 6 months and maintained in media containing 5µM drug, referred to as LNCaP/C42B ENZU cells. Gene set enrichment analysis of differentially expressed genes (DEGs) demonstrated an overlap between genes of metabolic signaling pathways together with fatty acid signaling, fatty acid β oxidation, drug resistance, bile acid biosynthesis, lipid metabolism, and peroxisome signaling. Interestingly, NGS data of LNCaP-ENZU cells showed a higher number of DEGs genes associated with metabolic reprogramming, compared to C42B-ENZU cells. Analysis of LNCaP-ENZU cells exhibited more than 10 fold higher (log2 fold) expression of XIST, AKT3, ZNF655, IRS4, HOXB3, FBN2, FHL1, GSTP1, VCAN, KIAA0408 genes; whereas ZNF544, KLK2, CSMD1, ZG16B, SPDEF, AR, C1R1, FOLH1, HISTIHIB, and TNPR222 were downregulated (-10 to -12 log2 fold), compared to parental counterpart. The majority of these genes belong to the metabolic regulatory network. Furthermore, genes viz. AKT3, HOXB3, and KIA0048 RALYL and KLK2 exhibited interaction with androgen receptor (AR), and may influence the ligand-binding domain of AR resulting in stimulation of AR/AR targeted genes. Q-PCR data were in agreement with NGS data where the signature genes associated with the metabolic synthesis of fatty acid, lipid and glucose were overexpressed in LNCaP-ENZU cells. In particular, fatty acid synthesis genes viz. ACADL, ACSL4, FHL2, and SLC27A6 were high up to 14.7, 15.8, 6.02 and 17.8 log2 fold value. Expression of solute carrier SLC12A5, SLC13A4, SLC24A4, SLC30A3, SLC35D1, and SLC47A1 genes showed 1195, 5, 20.01, 4.6, 9.5, and 4.3 log2 fold higher expression, which function in increasing the nucleotide-sugar transmembrane transporter activity. Expression of lipid-associated genes viz. ABCB4, CYP2D6, CYP4X1, CYP39A1, and SLC25A17 exhibited 30, 25.6, 25.5, 8.4, and 17.5 log2 fold higher expression. These gene expression correlated with higher-end products of TCA cycle, glucose metabolism, citric acid and lactate production in LNCaP ENZU-resistant cells. Taken together, our findings demonstrate molecular alterations after enzalutamide exposure may provide fuel to the cells through metabolic reprogramming. Clinically, targeting the aforementioned genes associated with metabolic reprogramming may lead to control of the enzalutamide-mediated recurrence of prostate cancer. Citation Format: Shiv S. Verma, Eswar Shankar, Rajnee Kanwal, Ricky Chan, Sanjay Gupta. Metabolic reprogramming fuels prostate cancer cells towards enzalutamide resistance [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1467.

Abstract 1262: Targeting transcriptional addiction in anti-androgen refractory castration-resistant prostate cancer

Abstract Prostate cancer (PCa) is the second leading cause of cancer-related mortality in men of the western world. Androgen receptor (AR) is the primary driver alteration in metastatic castration-resistant prostate cancer (mCRPC). Advanced PCa treated with first line androgen-deprivation therapy (ADT) eventually relapse in a hormone refractory or castration-resistant (CR) form. Relapsed disease is highly aggressive and poses an increased risk of morbidity and death. This refractory state of CRPC is characterized by a strong addiction to AR-mediated transcription driven by the synergy between a variety of genomic alterations and epigenetic remodeling. Despite the success of recently approved therapies targeting AR signaling, such as abiraterone and second-generation anti-androgens including enzalutamide, durable responses are limited, owing to acquired resistance. Epigenetic therapies targeting coactivators within the AR transcription machinery have shown promise as effective options for the treatment of CRPC in both its naive and Enzalutamide Resistant state (Enza-Res). Using basic proteomic and next generation genomic approaches, we have identified CDK7, as an indispensable component of the AR-transcription machinery and a novel target in CRPC. The phosphorylation of MED1 (T1457) by CDK7 leads to the formation of the chromatin bound AR-MED1 complex and is essential for its stability and onset of AR-mediated transcription. Loss of CDK7 activity either through genetic silencing or through treatment with the CDK7 inhibitor THZ1 led to de-recruitment of chromatin bound MED1, loss of AR-target gene expressions, increased apoptosis, and a drastic reduction in cell proliferation. Here, we present evidence for the efficacy of targeting CDK7 in curtailing AR signaling in the Enza-Res state. Further, we observed hyper-phosphorylation of MED1 and AR, and a concomitant decrease in the catalytic-subunit (alpha-isoform) of the protein phosphatase 2A (PP2ACα) in enzalutamide resistant cell lines and metastatic biopsies. This hyper-phosphorylated state was strongly dependent on the catalytic activity of CDK7, wherein treatment of Enza-Res cells with THZ1 led to complete loss of phosphorylation of MED1 and AR, and death in Enza-res cells. These findings point to the indispensable role of CDK7 in driving the AR oncogenic transcription program in anti-androgen refractory CRPC and its viability as a potential therapeutic target. Citation Format: Reyaz ur Rasool, Ramakrishnan Natesan, Qu Deng, Shweta Aras, Samuel Sander Effron, Samuel Sander Effron, Erick Mitchell Velasquez, Jessica M. Posimo, Priti Lal, Donita C. Brady, Irfan A. Asangani. Targeting transcriptional addiction in anti-androgen refractory castration-resistant prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1262.

Combination therapy with androgen receptor N-terminal domain antagonist EPI-7170 and enzalutamide yields synergistic activity in AR-V7-positive prostate cancer.

Resistance of castration-resistant prostate cancer (CRPC) to enzalutamide and abiraterone involves the expression of constitutively active, truncated androgen receptor (AR) splice variants (AR-Vs) that lack a C-terminal ligand-binding domain (LBD). Both full-length AR and truncated AR-Vs require a functional N-terminal domain (NTD) for transcriptional activity thereby providing rationale for the development of ralaniten (EPI-002) as a first-in-class antagonist of the AR-NTD. Here, we evaluated the antitumor effect of a next-generation analog of ralaniten (EPI-7170) as a monotherapy or in combination with enzalutamide in prostate cancer cells that express AR-V7 that were resistant to enzalutamide. EPI-7170 had 8-9 times improved potency compared to ralaniten. Enzalutamide increased levels of AR-V7 and expression of its target genes. Knockdown of AR-V7 restored sensitivity to enzalutamide, indicating a role for AR-V7 in the mechanism of resistance. EPI-7170 inhibited expression of genes transcriptionally regulated by full-length AR and AR-V7. A combination of EPI-7170 and enzalutamide resulted in synergistic inhibition of proliferation of enzalutamide-resistant cells that was consistent with results from cell cycle and clonogenic assays. In addition, this drug enhanced the antitumor effect of enzalutamide in enzalutamide-resistant CRPC preclinical models. Thus, a combination therapy targeting both the NTD and LBD of AR, and thereby blocking both full-length AR and AR-Vs, has potential for the treatment of enzalutamide-resistant CRPC.

Cross-Resistance Among Next-Generation Antiandrogen Drugs Through the AKR1C3/AR-V7 Axis in Advanced Prostate Cancer.

The next-generation antiandrogen drugs, XTANDI (enzalutamide), ZYTIGA (abiraterone acetate), ERLEADA (apalutamide) and NUBEQA (darolutamide) extend survival times and improve quality of life in patients with advanced prostate cancer. Despite these advances, resistance occurs frequently and there is currently no definitive cure for castration-resistant prostate cancer. Our previous studies identified that similar mechanisms of resistance to enzalutamide or abiraterone occur following treatment and cross-resistance exists between these therapies in advanced prostate cancer. Here, we show that enzalutamide- and abiraterone-resistant prostate cancer cells are further cross-resistant to apalutamide and darolutamide. Mechanistically, we have determined that the AKR1C3/AR-V7 axis confers this cross-resistance. Knockdown of AR-V7 in enzalutamide-resistant cells resensitize cells to apalutamide and darolutamide treatment. Furthermore, targeting AKR1C3 resensitizes resistant cells to apalutamide and darolutamide treatment through AR-V7 inhibition. Chronic apalutamide treatment in C4-2B cells activates the steroid hormone biosynthesis pathway and increases AKR1C3 expression, which confers resistance to enzalutamide, abiraterone, and darolutamide. In conclusion, our results suggest that apalutamide and darolutamide share similar resistant mechanisms with enzalutamide and abiraterone. The AKR1C3/AR-V7 complex confers cross-resistance to second-generation androgen receptor-targeted therapies in advanced prostate cancer.

MiR-5089-5p suppresses castration-resistant prostate cancer resistance to enzalutamide and metastasis via miR-5089-5p/SPINK1/ MAPK/MMP9 signaling.

Whether serine protease inhibitor Kazal type 1 (SPINK1) being associated with enzalutamide (Enz) resistance and metastasis of castration-resistant prostate cancer (CRPC) has not been clear. SPINK1 promoted Enz resistance by upregulating Androgen receptor splicing variant 7 (ARv7), and enhanced the invasion/migration of Enz-resistant cells via ERK/p38/ MMP9 signaling. Furthermore, miR-5089-5p suppressed SPINK1 mRNA through direct binding to its 3'UTR, and reversed its pro-proliferative and pro-metastatic effects. Mice bearing SPINK1-knockdown Enz-resistant PCa tumors showed significantly longer survival compared with those bearing wild-type tumors, while treatment with miR-5089-5p inhibitor abrogated the protective effects of SPINK1 knockdown. Taken together, SPINK1 can be used as a biomarker of resistance to Enz, and the miR-5089-5p/SPINK1/MAPK/MMP9 axis is a suitable therapeutic target against Enz-resistant and metastatic CRPC.Methods: The expression of SPINK1 in Enz-resistant prostate cancer (PCa) cell lines was detected through next-generation sequencing data and metastatic PCa patients. In vivo and in vitro experiments were performed to investigate the role of SPINK1 in Enz-resistance and metastasis.

Ralaniten Sensitizes Enzalutamide-Resistant Prostate Cancer to Ionizing Radiation in Prostate Cancer Cells that Express Androgen Receptor Splice Variants

Blocking androgen receptor (AR) transcriptional activity by androgen deprivation therapy (ADT) improves the response to radiotherapy for intermediate and high risk prostate cancer. Unfortunately, ADT, antiandrogens, and abiraterone increase expression of constitutively active splice variants of AR (AR-Vs) which regulate DNA damage repair leading to resistance to radiotherapy. Here we investigate whether blocking the transcriptional activities of full-length AR and AR-Vs with ralaniten leads to enhanced sensitivity to radiotherapy. Combination therapies using ralaniten with ionizing radiation were evaluated for effects on proliferation, colony formation, cell cycle, DNA damage, and Western blot analyses in human prostate cancer cells that express both full-length AR and AR-Vs. Ralaniten and a potent next-generation analog (EPI-7170) decreased expression of DNA repair genes whereas enzalutamide had no effect. FACS analysis revealed a dose-dependent decrease of BrdU incorporation with increased accumulation of γH2AX with a combination of ionizing radiation with ralaniten. An additive inhibitory effect on proliferation of enzalutamide-resistant cells was achieved with a combination of ralaniten compounds with ionizing radiation. Ralaniten and EPI-7170 sensitized prostate cancer cells that express full-length AR and AR-Vs to radiotherapy whereas enzalutamide had no added benefit.

Inhibition of Rac1 reverses enzalutamide resistance in castration-resistant prostate cancer.

Enzalutamide, an androgen receptor inhibitor, has been clinically approved for the treatment of metastatic castration-resistant prostate cancer (CRPC) in the United States. However, patients only benefit from enzalutamide for a short period of time as resistance may develop. Therefore, it is vital to develop a novel strategy to overcome enzalutamide resistance. Ras-related C3 botulinum toxin substrate 1 (Rac1), which is commonly upregulated in human cancer types, has been recognized as a key molecular component in tumorigenesis, invasion and metastasis. However, the role of Rac1 in enzalutamide-resistance in prostate cancer (PCa) remains unknown. In the present study, Rac1 was demonstrated to be upregulated in enzalutamide-resistant PCa cells, and Rac1 knockdown inhibited enzalutamide-resistant cell proliferation and colony formation. Western blotting results indicated that enzalutamide treatment downregulated the expression levels of JNK and activated transcription factor 2, as well as enhanced the Bax/Bcl-2 ratio and induced cleavage of poly-ADP ribose polymerase. Moreover, knockdown of Rac1 in MR49F cells significantly inhibited cell migration and invasion via the downregulation of Snail and the upregulation of E-cadherin. The results of a nude mouse xenograft tumor model using 22RV1 cells demonstrated that enzalutamide inhibited tumor growth after Rac1 knockdown dramatically, compared to vehicle and single treatment groups. Therefore, the present study provided novel evidence that Rac1 may serve a crucial role in enzalutamide resistance, and that targeting Rac1 may be a potential approach for the treatment of CRPC.

The MAO inhibitors phenelzine and clorgyline revert enzalutamide resistance in castration resistant prostate cancer

The antiandrogen enzalutamide (Enz) has improved survival in castration resistant prostate cancer (CRPC) patients. However, most patients eventually develop Enz resistance that may involve inducing the androgen receptor (AR) splicing variant 7 (ARv7). Here we report that high expression of monoamine oxidase-A (MAO-A) is associated with positive ARv7 detection in CRPC patients following Enz treatment. Targeting MAO-A with phenelzine or clorgyline, the FDA-approved drugs for antidepression, resensitize the Enz resistant (EnzR) cells to Enz treatment and further suppress EnzR cell growth in vitro and in vivo. Our findings suggest that Enz-increased ARv7 expression can transcriptionally enhance MAO-A expression resulting in Enz resistance via altering the hypoxia HIF-1α signals. Together, our results show that targeting the Enz/ARv7/MAO-A signaling with the antidepressants phenelzine or clorgyline can restore Enz sensitivity to suppress EnzR cell growth, which may indicate that these antidepression drugs can overcome the Enz resistance to further suppress the EnzR CRPC.

MP37-03 MODULATING HSP70/STUB1 MACHINERY BY NOVEL SMALL MOLECULES OVERCOMES ENZALUTAMIDE RESISTANCE IN LETHAL PROSTATE CANCER

You have accessJournal of UrologyProstate Cancer: Advanced (including Drug Therapy) III (MP37)1 Apr 2020MP37-03 MODULATING HSP70/STUB1 MACHINERY BY NOVEL SMALL MOLECULES OVERCOMES ENZALUTAMIDE RESISTANCE IN LETHAL PROSTATE CANCER Chengfei Liu*, Wei Lou, Joy C. Yang, Shu Ning, Clifford Tepper, Pui-Kai Li, Christopher P. Evans, and Allen C. Gao Chengfei Liu*Chengfei Liu* More articles by this author , Wei LouWei Lou More articles by this author , Joy C. YangJoy C. Yang More articles by this author , Shu NingShu Ning More articles by this author , Clifford TepperClifford Tepper More articles by this author , Pui-Kai LiPui-Kai Li More articles by this author , Christopher P. EvansChristopher P. Evans More articles by this author , and Allen C. GaoAllen C. Gao More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000000886.03AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: Protein homeostasis is altered during prostate cancer progression mediated by a comphrehensive network including the ubiquitin-proteasome-system. This effect is primarily due to the modulation of the HSP70/STUB1 machinery which regulates AR/AR-V7 protein stability in advanced prostate cancer. Emerging evidence suggested that HSP70 protects AR-V7 from degradation induced by STUB1 in anti-androgen resistant prostate cancer cells. HSP70/STUB1 machinery controls cell sensitivity to enzalutamide and abiraterone treatment via AR-V7 proteostasis. Modulating HSP70/STUB1 could be a valuable strategy to overcome the resistance. METHODS: Gene expression was determined by qRT-PCR and western blot. Expression of HSP70 and STUB1 was downregulated using specific siRNA. HSP70/STUB1 and AR/AR-V7 interaction was determined by co-immunoprecipitation and dual immunofluorescence. The gene regulating mechanisms in drug resistant prostate cancer cells was determined by RNA sequencing analyses. The effects of drug treatment on enzalutamide sensitivity were examined in vitro and in vivo. RESULTS: In the present study, we discovered that HSP70/STUB1 machinery is involved in AR and AR-V7 protein stabilization and confers anti-androgen resistance. Modulating HSP70/STUB1 by small molecules (HSMs) re-sensitizes the resistant cells or xenograft tumors to anti-androgen treatment. Mechanistically, HSMs inhibit HSP70 and degrade AR-V7 protein through alteration of the ubiquitin-proteasome-system in enzalutamide resistant cells. HSMs promote STUB1 entering into the nuclear and binding to AR-V7. HSMs robustly disrupt HSP70 gene programs and suppress AR/AR-V7 target genes expression. Furthermore, we identified and characterized HSM-7 (one of the small molecules) that has a superior pharmacokinetics profile and is highly effective for the treatment of anti-androgen resistant prostate cancer both in vitro and in vivo. CONCLUSIONS: Modulating HSP70/STUB1 machinery by HSMs overcomes enzalutamide resistance through AR/AR-V7 regulation. Further development of HSM-7 may yield a novel therapeutics for the treatment of anti-androgen resistant prostate cancer. Source of Funding: This work was supported in part by grants NIH/NCI CA225836, CA168601, CA179970, and DOD PCRP PC150040. © 2020 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 203Issue Supplement 4April 2020Page: e561-e561 Advertisement Copyright & Permissions© 2020 by American Urological Association Education and Research, Inc.MetricsAuthor Information Chengfei Liu* More articles by this author Wei Lou More articles by this author Joy C. Yang More articles by this author Shu Ning More articles by this author Clifford Tepper More articles by this author Pui-Kai Li More articles by this author Christopher P. Evans More articles by this author Allen C. Gao More articles by this author Expand All Advertisement PDF downloadLoading ...

The Impact of Cand1 in Prostate Cancer.

Evidence has accumulated asserting the importance of cullin-RING (really interesting new gene) ubiquitin ligases (CRLs) and their regulator Cullin-associated neural-precursor-cell-expressed developmentally down-regulated 8 (NEDD8) dissociated protein 1 (Cand1) in various cancer entities. However, the role of Cand1 in prostate cancer (PCa) has not been intensively investigated so far. Thus, in the present study, we aimed to assess the relevance of Cand1 in the clinical and preclinical setting. Immunohistochemical analyses of radical prostatectomy specimens of PCa patients showed that Cand1 protein levels are elevated in PCa compared to benign areas. In addition, high Cand1 levels were associated with higher Gleason Scores, as well as higher tumor recurrence and decreased overall survival. In line with clinical findings, in vitro experiments in different PCa cell lines revealed that knockdown of Cand1 reduced cell viability and proliferation and increased apoptosis, therefore underlining its role in tumor progression. We also found that the cyclin-dependent kinase inhibitor p21 is significantly upregulated upon downregulation of Cand1. Using bioinformatic tools, we detected genes encoding for proteins linked to mRNA turnover, protein polyubiquitination, and proteasomal degradation to be significantly upregulated in Cand1high tumors. Next generation sequencing of PCa cell lines resistant to the anti-androgen enzalutamide revealed that Cand1 is mutated in enzalutamide-resistant cells, however, with little functional and clinically relevant impact in the process of resistance development. To summarize the present study, we found that high Cand1 levels correlate with PCa aggressiveness.

Cancer-associated fibroblasts promote prostate tumor growth and progression through upregulation of cholesterol and steroid biosynthesis

BackgroundAndrogen receptor targeted therapies have emerged as an effective tool to manage advanced prostate cancer (PCa). Nevertheless, frequent occurrence of therapy resistance represents a major challenge in the clinical management of patients, also because the molecular mechanisms behind therapy resistance are not yet fully understood. In the present study, we therefore aimed to identify novel targets to intervene with therapy resistance using gene expression analysis of PCa co-culture spheroids where PCa cells are grown in the presence of cancer-associated fibroblasts (CAFs) and which have been previously shown to be a reliable model for antiandrogen resistance.MethodsGene expression changes of co-culture spheroids (LNCaP and DuCaP seeded together with CAFs) were identified by Illumina microarray profiling. Real-time PCR, Western blotting, immunohistochemistry and cell viability assays in 2D and 3D culture were performed to validate the expression of selected targets in vitro and in vivo. Cytokine profiling was conducted to analyze CAF-conditioned medium.ResultsGene expression analysis of co-culture spheroids revealed that CAFs induced a significant upregulation of cholesterol and steroid biosynthesis pathways in PCa cells. Cytokine profiling revealed high amounts of pro-inflammatory, pro-migratory and pro-angiogenic factors in the CAF supernatant. In particular, two genes, 3-hydroxy-3-methylglutaryl-Coenzyme A synthase 2 (HMGCS2) and aldo-keto reductase family 1 member C3 (AKR1C3), were significantly upregulated in PCa cells upon co-culture with CAFs. Both enzymes were also significantly increased in human PCa compared to benign tissue with AKR1C3 expression even being associated with Gleason score and metastatic status. Inhibiting HMGCS2 and AKR1C3 resulted in significant growth retardation of co-culture spheroids as well as of various castration and enzalutamide resistant cell lines in 2D and 3D culture, underscoring their putative role in PCa. Importantly, dual targeting of cholesterol and steroid biosynthesis with simvastatin, a commonly prescribed cholesterol synthesis inhibitor, and an inhibitor against AKR1C3 had the strongest growth inhibitory effect.ConclusionsFrom our results we conclude that CAFs induce an upregulation of cholesterol and steroid biosynthesis in PCa cells, driving them into AR targeted therapy resistance. Blocking both pathways with simvastatin and an AKR1C3 inhibitor may therefore be a promising approach to overcome resistances to AR targeted therapies in PCa.3iMBuBncLfXKMeSSDowVrVVideo abstract

Abstract A110: Isothiocyanate-containing hybrid androgen receptor (AR) antagonist downregulates AR and induces ferroptosis in GSH–deficient prostate cancer cells

Abstract Androgen receptor (AR) over-expression, mutation and the emergence of AR splice variants (AR-Vs) promote disease-driving AR signaling in castration-resistant prostate cancer (CRPC). In addition to the sustained AR activation, apoptosis evasion adds extra hurdle for treating hormone refractory prostate cancer (PCa). To overcome these challenges, we firstly designed isothiocyanate (ITC)-containing hybrid AR antagonist (ITC-ARi) and then rationally combined ITC-ARi with glutathione (GSH) biosynthesis inhibitor buthionine sulphoximine (BSO) to efficiently downregulate AR/AR-V and induce ferroptosis in enzalutamide (Enz)-resistant PCa cells. Naturally occurring ITCs (e.g., sulforaphane and phenylethyl isothiocyanate) display pleotropic anti-PCa activities. A representative ITC-ARi 2-63 is designed by incorporating ITC into an AR ligand scaffold. The sulfhydryl reactivity of ITC is transiently masked as N-acetyl cysteine (NAC) conjugate that gradually releases parental free ITC in aqueous solution. 2-63 antagonizes AR transactivation, downregulates AR/AR-V7, and upregulates cellular stress markers Hsp70 and heme oxygenase-1 (HO-1), indicating the disruption of heat shock proteins (Hsps) and the activation of Nrf2 pathway. Because the anticancer effects of ITC/ITC-NAC conjugate are attenuated by GSH-participated conjugation or thiol exchange, we rationally combined 2-63 with BSO for enhanced anti-PCa activities. 2-63 and BSO synergistically reduce viability of multiple PCa cell lines (VCaP, C4-2 and 22Rv-1), and the noncancerous prostatic RWPE-1 cell is much less affected. Because 2-63 plus BSO does not upregulate typical apoptosis markers, we investigated alternative cell death mechanism in combinatorial treatment. Drug combination-caused cell viability loss is effectively rescued by iron chelator deferoxamine (DFO), antioxidants α-tocopherol (α-Toc) and ferrostatin-1 (Fer-1), or the inhibitor of HO-1 Zinc (II) protoporphyrin IX (ZnPP). Both Fer-1 and α-Toc are potent radical scavengers blocking lipid hydroperoxide generation, and ZnPP suppresses HO-1-catalyzed upregulation of intracellular Fe2+. The reverse of growth suppression by DFO, antioxidants and ZnPP supports the induction of ferroptosis, a regulated non-apoptotic cell death caused by reactive oxygen species (ROS)- and iron-dependent lipid peroxidation. 2-63 and BSO also more efficiently downregulate AR/AR-V than 2-63 alone in Enz-resistant PCa cells. Interestingly, ferroptosis-preventing DFO and Fer-1 do not rescue AR/AR-V7 and are unable to suppress the upregulation of Hsp70 and HO-1. Our results suggest that the synergism of 2-63 and BSO occurs through increasing drug accessibility to cellular targets, expanding availability of iron and potentially affecting glutathione peroxidase 4 (GPX4) activity, the most important cellular defense to eliminate lipid hydroperoxide. Combining ITC-ARi and GSH-depleting agents could be a new concept leading to effective CRPC treatment. Citation Format: Zhihui Qin, Liping Xu, Siyu Ou. Isothiocyanate-containing hybrid androgen receptor (AR) antagonist downregulates AR and induces ferroptosis in GSH–deficient prostate cancer cells [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr A110. doi:10.1158/1535-7163.TARG-19-A110

CircRNA-UCK2 Increased TET1 Inhibits Proliferation and Invasion of Prostate Cancer Cells Via Sponge MiRNA-767-5p.

A majority of the patients with advanced prostate cancer initially respond to androgen deprivation therapy and enzalutamide therapy, but eventually enter the castration-resistant prostate cancer (CRPC) phase. Some studies have shown that the activation of other signalling pathways in CRPC cells replaces the function of the androgen receptor, as well as promotes cell metastasis and progression. However, the mechanisms underlying this side effect remain unclear. The present study aims to explore the continued progression of cells after enzalutamide resistance. Low expression of circRNA-UCK2 (circUCK2) was detected in enzalutamide-resistant (EnzR) cells. Moreover, miR-767-5p was found to be resistant to EnzR cells when the level of circUCK2 is increased. The decrease in free miR-767-5p increases the expression of TET1 protein through the post-transcriptional regulation of mRNA, thereby inhibiting cell invasion and proliferation. Knocking down circUCK2 in enzalutamide-sensitive cells reduces the concentration of TET1, thereby increasing cell invasion and proliferation. A preclinical study using in vivo mouse models also showed that a high expression of circUCK2 inhibited the EnzR cell growth. Thus, this study might aid in developing a novel therapy to better suppress the CRPC progression.

Circular RNAs are differentially expressed in prostate cancer and are potentially associated with resistance to enzalutamide

Most forms of castration-resistant prostate cancer (CRPC) are dependent on the androgen receptor (AR) for survival. While, enzalutamide provides a substantial survival benefit, it is not curative and many patients develop resistance to therapy. Although not yet fully understood, resistance can develop through a number of mechanisms, such as AR copy number gain, the generation of splice variants such as AR-V7 and mutations within the ligand binding domain (LBD) of the AR. circular RNAs (circRNAs) are a novel type of non-coding RNA, which can regulate the function of miRNA, and may play a key role in the development of drug resistance. circRNAs are highly resistant to degradation, are detectable in plasma and, therefore may serve a role as clinical biomarkers. In this study, AR-V7 expression was assessed in an isogenic model of enzalutamide resistance. The model consisted of age matched control cells and two sub-line clones displaying varied resistance to enzalutamide. circRNA profiling was performed on the panel using a high throughout microarray assay. Bioinformatic analysis identified a number of differentially expressed circRNAs and predicted five miRNA binding sites for each circRNA. miRNAs were stratified based on known associations with prostate cancer, and targets were validated using qPCR. Overall, circRNAs were more often down regulated in resistant cell lines compared with control (588 vs. 278). Of particular interest was hsa_circ_0004870, which was down-regulated in enzalutamide resistant cells (p ≤ 0.05, vs. sensitive cells), decreased in cells that highly express AR (p ≤ 0.01, vs. AR negative), and decreased in malignant cells (p ≤ 0.01, vs. benign). The associated parental gene was identified as RBM39, a member of the U2AF65 family of proteins. Both genes were down-regulated in resistant cells (p < 0.05, vs. sensitive cells). This is one of the first studies to profile and demonstrate discrete circRNA expression patterns in an enzalutamide resistant cell line model of prostate cancer. Our data suggests that hsa_circ_0004870, through RBM39, may play a critical role in the development of enzalutamide resistance in CRPC.

Abstract 3005: High density lipoprotein mimics inhibit prostate cancer exosome-mediated communication with myeloid cells

Abstract Introduction: Exosomes are 30-150 nm membrane-bound vesicles that mediate intercellular communication and are secreted in abundance by neoplastic cells. Tumor-derived exosomes are capable of transmitting pro-malignant signals to target cells at local or distant sites to enhance tumor invasiveness and promote metastasis. A sub-set of this pro-malignant intercellular communication is dependent upon target cell cholesterol homeostasis. Here, we show that prostate cancer exosome communication with myeloid cells can be inhibited by treatment with high density lipoprotein mimetic nanoparticles (HDL NPs), which reduce cholesterol in myeloid cells in a targeted fashion. Methods: Exosomes were isolated by ultracentrifugation of conditioned media from enzalutamide resistant CWR-R1 cells and used for all experiments. In vitro assays were conducted using murine bone marrow macrophages obtained from culture of total murine bone marrow in M-CSF for 7 days. Confocal microscopy and flow cytometry were used for in vitro and in vivo uptake assays. Osteoclastogenesis assays were performed using a commercially available TRAP staining kit (Sigma-Aldrich). NF-kB signaling experiments were performed using a reporter human monocyte cell line (THP1-Dual). HDL NPs were synthesized using 5 nm gold nanoparticle templates, apolipoprotein A-1, and phospholipids. Results: HDL NPs were found to inhibit the cellular uptake of prostate cancer exosomes in mouse bone marrow macrophages in vitro. Furthermore, HDL NPs inhibited exosome-induced osteoclastogenesis and exosome-induced monocyte NF-kB signaling. Finally, HDL NP-mediated inhibition of exosome communication was found to be dependent upon scavenger receptor type B-1 (SR-B1). SR-B1 was shown to be expressed ubiquitously in mouse bone marrow macrophages; and HDL NPs were unable to inhibit exosome communication in bone marrow macrophages derived from SR-B1-/- mouse bone marrow. Conclusion: These data demonstrate that HDL NPs inhibit prostate cancer exosome communication with murine myeloid cells, as evidenced by cellular uptake, osteoclastogenesis, and NF-kB signaling. Moreover, SR-B1 is required for HDL NP inhibition of PCa exosome communication. In sum, these results indicate that target cell cholesterol homeostasis may be important for exosome-mediated signaling in prostate cancer, particularly in immune cells and in the bone microenvironment, and that HDL NPs are potent inhibitors of PCa exosome-mediated signaling. Citation Format: Stephen E. Henrich, Kaylin M. McMahon, Michael P. Plebanek, C. Shad Thaxton. High density lipoprotein mimics inhibit prostate cancer exosome-mediated communication with myeloid cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3005.

Abstract 4842: Overcoming EGFR and ERK-mediated resistance to enzalutamide in castration-resistant prostate cancer

Abstract The present project was undertaken to determine whether the activation of the EGFR family (EGFR/ErbB2/ErbB3/ErbB4) and its downstream signaling effector ERK1/2 plays a role in enzalutamide resistance and whether treatment with ErbB or ERK inhibitors overcome this resistance. C4-2B (enzalutamide sensitive) and 22Rv1 (partially enzalutamide resistant) cell lines cultured for prolonged periods in enzalutamide, developed resistance to this drug (C4-2B/MDVR and 22Rv1/MDVR, respectively). Whole genome comparison of enza-resistant to parental lines demonstrated that the ErbB signaling network was significantly upregulated in the enza-resistant lines. Comparison of various enza-sensitive and resistant lines demonstrated a strong correlation between phosphorylation at EGFR(Y1068) and enza resistance. Inhibition of EGFR, but not that of ErbB2 or ErbB3 prevented cell viability. The EGFR inhibitors erlotinib and dacomitinib, but not the ErbB2 inhibitor lapatinib, suppressed viability in combination with enzalutamide. We hypothesized that enza-resistant tumors expressing higher levels of EGFR would be more responsive to erlotinib. To test this hypothesis, we compared the effects of erlotinib and enzalutamide, individually or in combination, in organelles from PDX tumors expressing high or low EGFR levels. Significantly, tumors expressing high EGFR, but not those expressing low EGFR, were responsive to the combination. Finally, we investigated the cause for greater efficacy with erlotinib compared to lapatinib in PCa. Comparison of the effects of different ligands revealed that while both lapatinib and erlotinib inhibited EGFR phosphorylation, only erlotinib but not lapatinib was able to inhibit EGF-induced ERK phosphorylation. This indicated an important role for ERK in the mediation of EGFR ligand induced enzalutamide resistance. Continuous culture of enza-sensitive C4 cells in enzalutamide resulted in the development of ERK phosphorylation in these PTEN-null cells that normally do not express phosphorylated ERK, and the newly ERK phosphorylated cells also were more susceptible to erlotinib as well. In support of a role for ERK in mediating the effects of EGFR activation in enza-resistant cells, inhibition of EGFR but not ErbB2 or ErbB3 inhibited ERK phosphorylation, and the ERK inhibitor ulitertinib inhibited viability of enza-resistant lines. We conclude that enzalutamide treatment causes an increase in EGFR ligands that result in the phosphorylation of EGFR at Y1068, which further resulted in phosphorylation of ERK. EGFR inhibitors that prevent ERK phosphorylation were effective in suppressing viability of enza-resistant CRPC cells, whereas ErbB2 inhibitors that did not affect ERK phosphorylation were unable to affect cell viability. These results demonstrate why certain ErbB inhibitors failed to affect enza-resistant CRPC tumors but provide encouragement for others. Citation Format: Thomas M. Steele, Maitreyee K. Jathal, Salma Siddiqui, Sisi Qin, Clifford G. Tepper, Ralph W. deVere White, Manish Kohli, Liewei Wang, Allen C. Gao, Paramita M. Ghosh. Overcoming EGFR and ERK-mediated resistance to enzalutamide in castration-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4842.

Abstract 1020: p300 and CBP targeting in castration therapy resistant prostate cancer

Abstract p300 and CBP interact with transcription factors and other proteins via their histone acetyltransferase domain (HAT) and a bromodomain (Bd). In prostate cancer, p300 and CBP act as oncogenes and are commonly upregulated. p300 and CBP are valid targets for therapy due to their function as androgen receptor (AR) coactivators and involvement in castration resistance. Revealing downstream pathways and their function in cancer cell proliferation and resistance should further identify potential novel therapeutic targets. The effect of the p300/CBP HAT inhibitor C646 and the Bd inhibitor ICBP-112 on viability was tested. To this end several human PCa cell lines with different AR expression levels and resistance status were used. The resistant cells were derived from DUCaP, LAPC4 and LNCaP cells chronically treated with Enzalutamide (DUCaP ENZA, LAPC4 ENZA and LNCaP ABL ENZA). Resistance was verified by viability assay. Regulation of AR downstream targets was studied by qRT-PCR and Western blot. Gene expression in the different DUCaP and LNCaP sublines after inhibitor treatment was analyzed with RNAseq. Both inhibitors exhibited IC50 values on viability at micromolar concentrations with a significantly lesser effect on androgen-insensitive PC3 cells compared to AR sensitive cells. Significantly increased sensitivity to inhibitors was observed in enzalutamide-resistant DUCaP ENZA, LAPC4 ENZA and LNCaP ABL ENZA cell lines relative to parental cells: respectively 1.83- (*), 2- (*) and 2.7-fold (*) for C646 and not significant, 1.8- (p&amp;lt;0.1) and 1.56-fold (*) for ICBP-112. Moreover, ICBP-112 treatment of DUCaP cells significantly reduced expression of the AR target genes FKBP5, PSA and TMPRSS2 0.6- (**), 0.57- (**) and 0.37-fold (***) respectively. Similar results were obtained with DUCaP ENZA cells 0.46- (*), 0.45- (*) and 0.57-fold (ns) for FKBP5, PSA and TMPRSS2, respectively. Whilst less pronounced, this regulation was also observed at the protein level. Similar results were obtained with C646. RNAseq results suggest multiple changes in sublines after chronic enzalutamide treatment in DUCaP and LNCaP cells. Inhibition of p300 and CBP reduced androgen-, myc- and parts of an EMT-signature, which are likely involved in the development of enzalutamide resistance. Taken together, C646 and ICBP-112 are effective inhibitors of AR dependent PCa. Furthermore, differences between cell lines suggest that the AR background and other factors influence the inhibitor effectivity. A significantly increased effect of the HAT and Bd inhibitors in CRPC suggests an important role for p300/CBP in CRPC. Citation Format: Tobias Furlan, Natalie Sampson, Frédéric R. Santer, Zoran Culig. p300 and CBP targeting in castration therapy resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1020.