Preclinical Models Of Prostate Cancer Research Articles

Snail promotes resistance to enzalutamide through regulation of androgen receptor activity in prostate cancer.

Treatment with androgen-targeted therapies can induce upregulation of epithelial plasticity pathways. Epithelial plasticity is known to be important for metastatic dissemination and therapeutic resistance. The goal of this study is to elucidate the functional consequence of induced epithelial plasticity on AR regulation during disease progression to identify factors important for treatment-resistant and metastatic prostate cancer. We pinpoint the epithelial plasticity transcription factor, Snail, at the nexus of enzalutamide resistance and prostate cancer metastasis both in preclinical models of prostate cancer and in patients. In patients, Snail expression is associated with Gleason 9-10 high-risk disease and is strongly overexpressed in metastases as compared to localized prostate cancer. Snail expression is also elevated in enzalutamide-resistant prostate cancer cells compared to enzalutamide-sensitive cells, and downregulation of Snail re-sensitizes enzalutamide-resistant cells to enzalutamide. While activation of Snail increases migration and invasion, it is also capable of promoting enzalutamide resistance in enzalutamide-sensitive cells. This Snail-mediated enzalutamide resistance is a consequence of increased full-length AR and AR-V7 expression and nuclear localization. Downregulation of either full-length AR or AR-V7 re-sensitizes cells to enzalutamide in the presence of Snail, thus connecting Snail-induced enzalutamide resistance directly to AR biology. Finally, we demonstrate that Snail is capable of mediating-resistance through AR even in the absence of AR-V7. These findings imply that increased Snail expression during progression to metastatic disease may prime cells for resistance to AR-targeted therapies by promoting AR activity in prostate cancer.

Clinical activity of ONC201 in metastatic castrate resistant prostate cancer (mCRPC).

e16514Background: Proteasome inhibitors that induce the integrated stress response are effective in preclinical models of hormone-refractory prostate cancer and have induced objective responses in ...

Automated synthesis of [(18)F]DCFPyL via direct radiofluorination and validation in preclinical prostate cancer models.

BackgroundProstate-specific membrane antigen (PSMA) is frequently overexpressed and upregulated in prostate cancer. To date, various 18F- and 68Ga-labeled urea-based radiotracers for PET imaging of PSMA have been developed and entered clinical trials. Here, we describe an automated synthesis of [18F]DCFPyL via direct radiofluorination and validation in preclinical models of prostate cancer.Methods[18F]DCFPyL was synthesized via direct nucleophilic heteroaromatic substitution reaction in a single reactor TRACERlab FXFN automated synthesis unit. Radiopharmacological evaluation of [18F]DCFPyL involved internalization experiments, dynamic PET imaging in LNCaP (PSMA+) and PC3 (PSMA−) tumor-bearing BALB/c nude mice, biodistribution studies, and metabolic profiling. In addition, reversible two-tissue compartmental model analysis was used to quantify pharmacokinetics of [18F]DCFPyL in LNCaP and PC3 tumor models.ResultsAutomated radiosynthesis afforded radiotracer [18F]DCFPyL in decay-corrected radiochemical yields of 23 ± 5 % (n = 10) within 55 min, including HPLC purification. Dynamic PET analysis revealed rapid and high uptake of radioactivity (SUV5min 0.95) in LNCaP tumors which increased over time (SUV60min 1.1). Radioactivity uptake in LNCaP tumors was blocked in the presence of nonradioactive DCFPyL (SUV60min 0.22). The muscle as reference tissue showed rapid and continuous clearance over time (SUV60min 0.06). Fast blood clearance of radioactivity resulted in tumor-blood ratios of 1.0 after 10 min and 8.3 after 60 min. PC3 tumors also showed continuous clearance of radioactivity over time (SUV60min 0.11). Kinetic analysis of PET data revealed the two-tissue compartmental model as best fit with K1 = 0.12, k2 = 0.18, k3 = 0.08, and k4 = 0.004 min−1, confirming molecular trapping of [18F]DCFPyL in PSMA+ LNCaP cells.Conclusions[18F]DCFPyL can be prepared for clinical applications simply and in good radiochemical yields via a direct radiofluorination synthesis route in a single reactor automated synthesis unit. Radiopharmacological evaluation of [18F]DCFPyL confirmed high PSMA-mediated tumor uptake combined with superior clearance parameters. Compartmental model analysis points to a two-step molecular trapping mechanism based on PSMA binding and subsequent internalization leading to retention of radioactivity in PSMA+ LNCaP tumors.Electronic supplementary materialThe online version of this article (doi:10.1186/s13550-016-0195-6) contains supplementary material, which is available to authorized users.

Editorial introductions

Current Opinion in Oncology was launched in 1989. It is one of a successful series of review journals whose unique format is designed to provide a systematic and critical assessment of the literature as presented in the many primary journals. The field of psychiatry is divided into 15 sections that are reviewed once a year. Each section is assigned a Section Editor, a leading authority in the area, who identifies the most important topics at that time. Here we are pleased to introduce the Journal's Section Editors for this issue. SECTION EDITORS Gilberto de Castro JrGilberto de Castro JrGilberto de Castro Jr received his MD degree from the University of Sao Paulo Medical School, Brazil in 1995, and completed his training in Internal Medicine and Clinical Oncology in 2000 at Hospital das Clínicas, University of Sao Paulo Medical School, where he also received his PhD degree in 2009. He is an ex fellow of the Medical Oncology Clinic at the Institut Jules Bordet, Brussels, Belgium. His current position is Chief at the Unit of Head and Neck and Thoracic Tumors of the Clinical Oncology Service of the Instituto do Cancer do Estado de Sao Paulo, Brazil - the largest cancer center in the South America. Dr Castro has more than 50 publications in peer-reviewed journals and his areas of interest are the medical management of head and neck cancer and thoracic malignancies, focusing on the development of molecular targeted therapies, predictive factors of response to chemotherapy, treatment-related toxicity and quality of life studies. Arif HussainArif HussainArif Hussain, MD is Professor of Medicine with Tenure in the Department of Medicine, School of Medicine, at the University of Maryland in Baltimore, USA, where he is also Professor of Biochemistry in the Department of Biological Chemistry and Professor of Pathology in the Department of Pathology. He also serves as Co-Leader of the Hormone Responsive Cancers Program in the Greenebaum Cancer Center, University of Maryland. Dr Hussain's clinical interest is in genitourinary cancers, and he serves as Principal Investigator on several clinical trials that focus on therapies for high risk, recurrent and metastatic prostate cancer, as well as renal cell cancer. In addition, he has a research laboratory focusing on drug resistance, intracellular calcium pumps, and pre-clinical models of prostate cancer.

Application of Small-Scale (Sub-Organ and Cellular Level) Alpha-Particle Specific Dosimetry Model in Tumors and Kidneys in a Pre-Clinical Model of Metastatic Prostate Cancer Using 211At-YC-I-27, a PSMA-Targeting Ligand for Metastatic Prostate Cancer

Application of Small-Scale (Sub-Organ and Cellular Level) Alpha-Particle Specific Dosimetry Model in Tumors and Kidneys in a Pre-Clinical Model of Metastatic Prostate Cancer Using 211At-YC-I-27, a PSMA-Targeting Ligand for Metastatic Prostate Cancer

Real-time monitoring of tumor progression and drug responses in a preclinical mouse model of prostate cancer.

Monitoring disease progression through imaging is playing an increasingly important role in the treatment of prostate cancer. Here, we report that primary mouse prostate cancer cell lines stably expressing luciferase and tumor biomarkers can be monitored through bioluminescence imaging along with assays of serum biomarkers and immune function. Tumorigenesis in immunocompetent C57BL/6 mice can be monitored in by collecting samples from the dorsal flank, dorsolateral prostate, and tail vein to obtain real-time subcutaneous, orthotopic, and metastasis indicators, respectively. We used this technique to confirm the therapeutic effect of immune checkpoint blockade. Our findings suggest the presented indicators are ideally suited for real-time tracking of drug responses, tumor progression and immune function.

Combined AKT and MEK Pathway Blockade in Pre-Clinical Models of Enzalutamide-Resistant Prostate Cancer.

Despite recent improvements in patient outcomes using newer androgen receptor (AR) pathway inhibitors, treatment resistance in castrate resistant prostate cancer (CRPC) continues to remain a clinical problem. Co-targeting alternate resistance pathways are of significant interest to treat CRPC and delay the onset of resistance. Both the AKT and MEK signaling pathways become activated as prostate cancer develops resistance to AR-targeted therapies. This pre-clinical study explores co-targeting these pathways in AR-positive prostate cancer models. Using various in vitro models of prostate cancer disease states including androgen dependent (LNCaP), CRPC (V16D and 22RV1) and ENZ-resistant prostate cancer (MR49C and MR49F), we evaluate the relevance of targeting both AKT and MEK pathways. Our data reveal that AKT inhibition induces apoptosis and inhibits cell growth in PTEN null cell lines independently of their sensitivity to hormone therapy; however, AKT inhibition had no effect on the PTEN positive 22RV1 cell line. Interestingly, we found that MEK inhibition had greater effect on 22RV1 cells compared to LNCaP, V16D or ENZ-resistant cells MR49C and MR49F cells. In vitro, combination AKT and MEK blockade had evidence of synergy observed in some cell lines and assays, but this was not consistent across all results. In vivo, the combination of AKT and MEK inhibition resulted in more consistent tumor growth inhibition of MR49F xenografts and longer disease specific survival compared to AKT inhibitor monotherapy. As in our in vitro study, 22RV1 xenografts were more resistant to AKT inhibition while they were more sensitive to MEK inhibition. Our results suggest that targeting AKT and MEK in combination may be a valuable strategy in prostate cancer when both pathways are activated and further support the importance of characterizing the dominant oncogenic pathway in each patient’s tumor in order to select optimal therapy.

MP62-12 ORTHOTOPIC XENOGRAFTS USING LUCAP136 SPHEROID CULTURES PROVIDE A VERSATILE PRECLINICAL MODEL OF PROSTATE CANCER

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology I1 Apr 2016MP62-12 ORTHOTOPIC XENOGRAFTS USING LUCAP136 SPHEROID CULTURES PROVIDE A VERSATILE PRECLINICAL MODEL OF PROSTATE CANCER Matthias Saar, Johannes Linxweiler, Maija Valta, Christina Körbel, Andreas Müller, Kerstin Junker, Michael Stöckle, Michael D. Menger, and Donna M Peehl Matthias SaarMatthias Saar More articles by this author , Johannes LinxweilerJohannes Linxweiler More articles by this author , Maija ValtaMaija Valta More articles by this author , Christina KörbelChristina Körbel More articles by this author , Andreas MüllerAndreas Müller More articles by this author , Kerstin JunkerKerstin Junker More articles by this author , Michael StöckleMichael Stöckle More articles by this author , Michael D. MengerMichael D. Menger More articles by this author , and Donna M PeehlDonna M Peehl More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.920AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Prostate cancer (PCa) research is still hampered by a limited number of well characterized models that adequately display intraprostatic tumor growth and progression. In this study we aimed to develop an authentic preclinical model of prostate cancer by combining an orthotopic xenografts with LuCaP136 spheroids - a recently developed 3D cell culture, that has some valuable properties like PTEN loss, TP53 mutation, wild-type AR and an osteosclerotic phenotype in intratibial xenograft models. METHODS 5x105 LuCaP136 spheroid cells were injected into the prostate of 6 CB17-SCID mice. Orthotopic tumor growth was monitored by 3D-ultrasonography (3D-US), contrast-enhanced in-vivo micro-CT (CE-CT) as well as 9.4T MRI. Furthermore, serum-PSA was measured 5 and 7 weeks after orthotopic implantation. After the sacrifice tumors were analyzed by conventional histology (H&E) as well as immunohistochemistry (IHC; PSA, AMACR, AR, ERG, Ki67). RESULTS Fast growing (doubling time = 12.4 days) orthotopic tumors developed in all mice and could be detected by 3D-US (Fig. 1A) and T2-weighted MRI (Fig. 1B) as early as 3 weeks after injection. Additionally acquired MRI sequences demonstrated restricted diffusion as it is typical for highly cellular tumors (DWI/ADC map; Fig. 1C) as well as intratumoral hemorrhage (T2*; Fig. 1D). CE-CT could not visualize the tumors properly. The mice had low but detectable PSA serum-levels with the mean almost doubling from the first (w5; 0.16ng/ml) to the second (w7; 0.29ng/ml) control. Tumor volumes determined by 3D-US and MRI showed a strong correlation among each other (r=0.963) as well as simultaneously measured PSA-levels (r=0.848 and r=0.844). At autopsy orthotopic tumors proved to be solid, highly vascularized (Fig. 1E) with signs of invasive growth. IHC showed positive AR, PSA and AMACR signals, ERG was negative. Ki67 proliferation index was close to 100% (Fig. 1F). CONCLUSIONS Orthotopic xenografts from LuCaP136 spheroids provide a realistic preclinical in-vivo model of PCa with multimodal imaging and serum-PSA serving as innovative tools to monitor tumor growth over time. Whether this model leads to the spontaneous development of especially osseous metastases is subject of current investigations. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e816-e817 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Matthias Saar More articles by this author Johannes Linxweiler More articles by this author Maija Valta More articles by this author Christina Körbel More articles by this author Andreas Müller More articles by this author Kerstin Junker More articles by this author Michael Stöckle More articles by this author Michael D. Menger More articles by this author Donna M Peehl More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Dietary pterostilbene is a novel MTA1-targeted chemopreventive and therapeutic agent in prostate cancer.

Overexpression of the epigenetic modifier metastasis-associated protein 1 (MTA1) is associated with aggressive human prostate cancer. The purpose of this study was to determine MTA1- targeted chemopreventive and therapeutic efficacy of pterostilbene, a natural potent analog of resveratrol, in pre-clinical models of prostate cancer. Here, we show that high levels of MTA1 expression in Pten-loss prostate cooperate with key oncogenes, including c-Myc and Akt among others, to promote prostate cancer progression. Loss-of-function studies using human prostate cancer cells indicated direct involvement of MTA1 in inducing inflammation and epithelial-to-mesenchymal transition. Importantly, pharmacological inhibition of MTA1 by pterostilbene resulted in decreased proliferation and angiogenesis and increased apoptosis. This restrained prostatic intraepithelial neoplasia (PIN) formation in prostate-specific Pten heterozygous mice and reduced tumor development and progression in prostate-specific Pten-null mice. Our findings highlight MTA1 as a key upstream regulator of prostate tumorigenesis and cancer progression. More significantly, it offers pre-clinical proof for pterostilbene as a promising lead natural agent for MTA1-targeted chemopreventive and therapeutic strategy to curb prostate cancer.

The microRNA-23b/-27b cluster suppresses prostate cancer metastasis via Huntingtin-interacting protein 1-related.

Deregulation of microRNAs (miRs) contributes to progression and metastasis of prostate and other cancers. miR-23b and -27b, encoded in the same miR cluster (miR-23b/-27b), are downregulated in human metastatic prostate cancer compared with primary tumors and benign tissue. Expression of miR-23b/-27b decreases prostate cancer cell migration, invasion and results in anoikis resistance. Conversely, antagomiR-mediated miR-23b and -27b silencing produces the opposite result in a more indolent prostate cancer cell line. However, neither miR-23b/-27b expression or inhibition impacts prostate cancer cell proliferation suggesting that miR-23b/-27b selectively suppresses metastasis. To examine the effects of miR-23b/-27b on prostate cancer metastasis in vivo, orthotopic prostate xenografts were established using aggressive prostate cancer cells transduced with miR-23b/-27b or non-targeting control miRNA. Although primary tumor formation was similar between miR-23b/-27b-transduced cells and controls, miR-23b/-27b expression in prostate cancer cells decreased seminal vesicle invasion and distant metastases. Gene-expression profiling identified the endocytic adaptor, Huntingtin-interacting protein 1-related (HIP1R) as being downregulated by miR-23b/-27b. Increased HIP1R expression in prostate cancer cells inversely phenocopied the effects of miR-23b/-27b overexpression on migration, invasion and anchorage-independent growth. HIP1R rescued miR-23b/-27b-mediated repression of migration in prostate cancer cells. HIP1R mRNA levels were decreased in seminal vesicle tissue from mice bearing miR-23b/-27b-transduced prostate cancer cell xenografts compared with scrambled controls, suggesting HIP1R is a key functional target of miR-23b/-27b. In addition, depletion of HIP1R led to a more rounded, less mesenchymal-like cell morphology, consistent with decreased metastatic properties. Together, these data demonstrate that the miR-23b/-27b cluster functions as a metastasis-suppressor by decreasing HIP1R levels in pre-clinical models of prostate cancer.

Multinucleation and Mesenchymal-to-Epithelial Transition Alleviate Resistance to Combined Cabazitaxel and Antiandrogen Therapy in Advanced Prostate Cancer.

Patients with metastatic castration-resistant prostate cancer (CRPC) frequently develop therapeutic resistance to taxane chemotherapy and antiandrogens. Cabazitaxel is a second-line taxane chemotherapeutic agent that provides additional survival benefits to patients with advanced disease. In this study, we sought to identify the mechanism of action of combined cabazitaxel and androgen receptor (AR) targeting in preclinical models of advanced prostate cancer. We found that cabazitaxel induced mitotic spindle collapse and multinucleation by targeting the microtubule depolymerizing kinesins and inhibiting AR. In androgen-responsive tumors, treatment with the AR inhibitor, enzalutamide, overcame resistance to cabazitaxel. Combination treatment of human CRPC xenografts with cabazitaxel and enzalutamide reversed epithelial-mesenchymal transition (EMT) to mesenchymal-epithelial transition (MET) and led to multinucleation, while retaining nuclear AR. In a transgenic mouse model of androgen-responsive prostate cancer, cabazitaxel treatment induced MET, glandular redifferentiation, and AR nuclear localization that was inhibited by androgen deprivation. Collectively, our preclinical studies demonstrate that prostate tumor resistance to cabazitaxel can be overcome by antiandrogen-mediated EMT-MET cycling in androgen-sensitive tumors but not in CRPC. Moreover, AR splice variants may preclude patients with advanced disease from responding to cabazitaxel chemotherapy and antiandrogen combination therapy. This evidence enables a significant insight into therapeutic cross-resistance to taxane chemotherapy and androgen deprivation therapy in advanced prostate cancer.

Spheroid culture of LuCaP 136 patient-derived xenograft enables versatile preclinical models of prostate cancer.

LuCaP serially transplantable patient-derived xenografts (PDXs) are valuable preclinical models of locally advanced or metastatic prostate cancer. Using spheroid culture methodology, we recently established cell lines from several LuCaP PDXs. Here, we characterized in depth the features of xenografts derived from LuCaP 136 spheroid cultures and found faithful retention of the phenotype of the original PDX. In vitro culture enabled luciferase transfection into LuCaP 136 spheroids, facilitating in vivo imaging. We showed that LuCaP 136 spheroids formed intratibial, orthotopic, and subcutaneous tumors when re-introduced into mice. Intratibial tumors responded to castration and were highly osteosclerotic. LuCaP 136 is a realistic in vitro-in vivo preclinical model of a subtype of bone metastatic prostate cancer.

Combined Akt and MEK pathway blockade in pre-clinical models of enzalutamide-resistant prostate cancer.

192 Background: Despite recent advances with newer androgen receptor(AR) pathway inhibitors, treatment resistance in castrate resistant prostate cancer continues to remain a clinical problem. Co-targeting approaches are of significant interest to slow the progression of disease and delay the onset of resistance. With both Akt and MEK pathways becoming activated as prostate cancer develops resistance to AR-targeted therapy, this study explores co-targeting these pathways in AR positive prostate cancer models. Methods: Using in vitro models of prostate cancer progression from androgen dependent to castrate resistant and ENZ-resistant disease, we evaluated the effect of Akt and/or MEK inhibition with AZD5363 and PD0325901, respectively, on cell proliferation, apoptosis and downstream signalling pathways. For in vivo models, we tested the combination of Akt and MEK inhibition castrated mice bearing MR49F and 22RV1 cells which are resistant to ENZ. Results: Inhibition of Akt reduced S6 phosphorylation, inhibited growth and induced apoptosis in LNCaP-derived cells; the addition of a MEK inhibitor increased apoptosis and cell cycle arrest, but did not further decrease cell proliferation. In contrast, PTEN wild-type 22RV1 cells demonstrated a greater sensitivity to MEK inhibition, but were generally insensitive to Akt inhibition. In vivo, combination of Akt and MEK inhibition resulted in more consistent tumour growth inhibition of MR49F xenografts and longer disease specific survival than Akt inhibitor monotherapy, with induction of pERK staining being evident in some AZD5363 monotherapy treated tumours. Conversely, 22RV1 xenografts had greater resistance to Akt inhibition and greater sensitivity to MEK inhibition. Conclusions: Our data suggest that combination of Akt and MEK inhibition may improve prostate cancer control in ENZ-resistant prostate cancer. Further, with the major effect in both MR49F and 22RV1 xenografts attributable to one inhibitor, our results also suggest the importance of characterizing the dominant oncogenic pathway in each patient’s tumour in order to select optimal therapy.

Abstract C132: Therapeutic reactivation of PP2A for prostate cancer treatment

Abstract Several new therapies have recently been approved for patients with castration-resistant prostate cancer (CRPC), however, none are curative and tumors ultimately develop resistance. Advances in the treatment of CRPC require novel approaches and therapies such as those outlined in this study. Most drug development efforts have focused on targeting single oncogenic proteins, an approach limited by the complexity of signaling networks and associated cross talk. Targeting phosphatases, the key negative regulators of signaling proteins, on the other hand, may overcome some of these limitations, particularly if these negative regulators themselves are altered.Through reverse engineering of tricyclic neuroleptic drugs, we have developed a series of small molecule activators of the serine/threonine phosphatase 2A (PP2A), a key negative regulator of numerous oncogenic signaling pathways. PP2A acts as a tumor suppressor and dephosphorylates several critical nodes in prostate cancer pathogenesis including the androgen receptor (AR). Decreased PP2A expression and/or activity have been correlated with castration-resistance in cell culture and human prostate cancer studies. These small molecule activators of PP2A (SMAPs), as represented by TRC-794, TRC-1154, and DT-061, directly bind and activate PP2A and have favorable pharmaceutical properties. In this study we sought to determine the activity of SMAPs in clinically relevant preclinical models of prostate cancer. Treatment of prostate cancer cell lines with SMAPs resulted in decreased cell viability and colony formation, cell cycle arrest, and an increase in apoptosis. Global Phosphoproteomic analysis of TRC-794 treated prostate cancer cells revealed that the AR and MYC were significantly perturbed in drug treated cells compared to controls which was subsequently confirmed by western blotting. Western blot analysis of prostate cancer cells demonstrated dose-dependent degradation of the AR resulting in PSA reduction and changes in canonical AR target gene expression. In order to investigate whether PP2A was mediating SMAP induced AR degradation, LNCAP cells were stably transduced with the SV40 small t antigen (ST), a potent oncoprotein that perturbs PP2A function. SMAPs were unable to degrade AR in LNCAP cells transduced with ST, suggesting that PP2A mediates SMAP induced AR degradation. SMAPs were evaluated in vivo in xenograft models representing prostate cancers that are sensitive to conventional therapy and resistant to enzalutamide, the current gold standard, due to overexpression of the AR or expression of androgen receptor splice variants (AR-SV). Single agent treatment with DT-1154 or DT-061 in vivo resulted in either significant tumor growth inhibition or tumor regression and induction of tumor cell apoptosis comparable to enzalutamide. Western blot analysis of the tumors demonstrated that the effects on tumor volume correlated strongly with target engagement as evidenced by significant decreases in PSA and AR expression in vivo. Additionally, these compounds demonstrated favorable pharmacokinetics and showed no overt toxicity. Combined these data highlight the potential for PP2A activation for both the treatment of CRPC and potentially for diverse PP2A inactivated tumor types and diseases. Citation Format: Kim McClinch, Rita Avelar, David Callejas, David Kastrinsky, Michael Ohlmeyer, Stephen Plymate, Matthew Galsky, Goutham Narla. Therapeutic reactivation of PP2A for prostate cancer treatment. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C132.

Docetaxel Resistance in Prostate Cancer: Taking It Up a Notch.

Notch signaling is implicated in prostate cancer progression and docetaxel resistance. Cui and colleagues describe the additive efficacy and mechanisms of a γ-secretase inhibitor, PF-03084014, and docetaxel in preclinical models of prostate cancer, suggesting the need for further clinical development of Notch pathway modulators in men with metastatic prostate cancer.

Tasquinimod in the treatment of castrate-resistant prostate cancer – current status and future prospects

Treatment options have significantly expanded in recent years for men with metastatic castration-resistant prostate cancer (mCRPC), with the routine use of immunotherapy (sipuleucel-T) and novel hormonal agents such as enzalutamide and abiraterone acetate prior to taxane-based chemotherapy or radium-223 radiotherapy. A number of immune checkpoints limit the immune response of the host to metastatic tumor progression in prostate cancer, one of which is an immunosuppressive and pro-angiogenic cell called the myeloid-derived suppressor cell (MDSC). Tasquinimod is a small molecular oral inhibitor of S100A9, a key cell surface regulator of MDSC function, and has shown anti-angiogenic, antitumor and immune-modulatory properties in preclinical models of prostate cancer and other solid tumors. A large randomized phase II trial of tasquinimod in men with chemotherapy-naïve mCRPC demonstrated a significant prolongation in radiographic and symptomatic progression-free survival compared with placebo, which was also associated with improvements in overall survival. Tasquinimod was studied in a global phase III randomized trial in men with bone mCRPC and, while it significantly improved radiographic progression-free survival, this did not result in an overall survival benefit. However, tasquinimod is under evaluation as well as a combination therapy with other systemic agents in prostate cancer and as a single agent in other solid tumors. This review encompasses the preclinical and clinical development of tasquinimod as a therapy for men with prostate cancer.

Prostate cancer: Novel xenografts in mice--a new wave of preclinical models.

Robust preclinical models of prostate cancer are required as clinical management of men with this disease evolves, and increasing genomic understanding makes currently available cell lines less relevant. A novel orthotopic xenograft mouse model is state of the art for preclinical models of prostate cancer.

Abstract 1845: Chloroquine demonstrates limited effectiveness in an autochthonous preclinical model of prostate cancer

Abstract Chloroquine (CQ) is a well-known compound that is used for the treatment of malaria and certain autoimmune diseases. CQ can also block autophagy, an essential cellular process that is implicated with resistance to chemotherapy. Preclinical studies have demonstrated the anticancer effects of CQ and hydroxychloroquine when used in combination with other anticancer agents suggesting that blocking autophagy inhibits therapeutic resistance. However, recent data shows that CQ can have antitumor effects independent of autophagy. Furthermore, given the specific roles of autophagy during tumorigenesis, the therapeutic effects of CQ observed in xenograft studies may differ than those in an autochthonous tumor model. The aim of our study was to investigate the antitumor effects of CQ in an autochthonous tumor model and to determine if CQ could reverse therapeutic resistance through the induction of autophagy. To test this hypothesis we tested the therapeutic administration of CQ in a genetically engineered mouse model of prostate cancer driven by the conditional inactivation of PTEN. We also characterized the combinatorial effects of CQ in combination with additional molecular targeting that included mTOR (everolimus), AKT (AZD5363), MEK (Selumetinib; AZD6244/ARRY142886), 5α-reductase (dutasteride) inhibitors. Oral administration of CQ demonstrated antitumor activity and moderately, but significantly, inhibited growth PTEN-deficient prostate tumors in a drug intervention model. However, combination therapy with CQ did not enhance therapeutic efficacy over inhibitor monotherapy alone. Mice with PTEN-mutant castration-resistant prostate cancer (CRPC) are resistant to treatment with everolimus. Therefore, we tested whether blocking autophagy could restore sensitivity to everolimus in CRPC. Mice with mutant PTEN and ATG7, an autophagy regulatory gene, CRPC demonstrated increased sensitivity and activity to everolimus suggesting that defective autophagy restored resistance to everolimus. On, the contrary, the treatment the combination of CQ and everolimus failed to produce any treatment effects in PTEN-deficient/ATG7-wildtype CRPC. Our findings suggest that combinatorial strategies with CQ lack therapeutic efficacy in autochthonous tumors and might be ineffective in the clinical setting. Citation Format: Yurie Kura, Marco A. De Velasco, Naomi Ando, Emiko Fukushima, Barry R. Davies, Dennis Huzdar, Yutaka Yamamoto, Yuji Hatanaka, Takashi Oki, Nobutaka Shimizu, Kazuhiro Yoshimura, Masahiro Nozawa, Kazuhiro Yoshikawa, Kazuto Nishio, Hirotsugu Uemura. Chloroquine demonstrates limited effectiveness in an autochthonous preclinical model of prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1845. doi:10.1158/1538-7445.AM2015-1845

Abstract 1857: Effects of long-term chloroquine chemotherapy in a preclinical model of PTEN-deficient prostate cancer

Abstract Chloroquine (CQ) and its derivative hydroxychloroquine are drugs that have been used to treat malaria and rheumatism. These drugs are also capable of producing antitumor effects in preclinical cancer models. In addition to mediating antitumor effects by impairing autophagy in certain cancer cells types, these agents have also been shown to effect antitumor responses independent of autophagy inhibition. Treatment strategies using CQ and its derivative alone or in combination with other anticancer drugs are being considered for clinical applications. However, the safety and long-term effects of CQ therapy for the treatment of cancers are unknown. In this study, we investigated the safety and efficacy of long-term CQ therapy in a PTEN-deficient model of prostate cancer. Twenty-eight-week-old tumor-bearing PTEN conditional knockout mice (PSA-CRE+/PTENf/f) were treated with CQ in the drinking water. Based on daily water consumption, the daily oral dose was adjusted to 100 mg/kg in distilled water. Timed sacrifices were scheduled 2, 4, 8, 16 and 32 weeks after the initiation of treatments and subset of mice was used for survival analysis. Mice receiving CQ were healthy in appearance and normal in demeanor. Compared to controls, mice receiving CQ began to exhibit lower body weights over the course of treatment beginning at 5 weeks after the initiation of treatment. At the completion of the study, mice receiving CQ averaged 27.3 grams of bodyweight compared to 33.8 grams in the control group (P<0.001). However, chronic treatment with CQ for 32 weeks inhibited tumor burden by 18.4% (P = 0.0118). For the long-term survival studies, median survival for control and CQ treated mice was 83.4 and 82.0 days, respectively (P = 0.782). Bodyweights of CQ mice were significantly reduced (44.8% of control, P = 0.029). Tumor burden at time of death decreased from 15.9% ±5.9 of bodyweight in control mice to 2.5% ±0.6 in CQ-treated mice (P<0.05). In summary, our studies show that long-term chronic administration of CQ was capable of inhibiting growth of PTEN-deficient tumors, however, CQ was poorly tolerated by mice and did not improve overall survival. Thus, caution should be exercised to carefully assess the safety and tolerability of this drug when using it long-term in human clinical trials. Citation Format: Kazuhiro Yoshikawa, Marco A. De Velasco, Yurie Kura, Naomi Ando, Emiko Fukushima, Yutaka Yamamoto, Yuji Hatanaka, Takashi Oki, Nobutaka Shimizu, Kazuhiro Yoshimura, Kazuto Nishio, Hirotsugu Uemura. Effects of long-term chloroquine chemotherapy in a preclinical model of PTEN-deficient prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1857. doi:10.1158/1538-7445.AM2015-1857

Abstract 1850: Evaluation of Pim-1 kinase inhibition in a preclinical model of mouse prostate cancer

Abstract Pim-1 is a serine/threonine kinase that is in involved in the transcription of genes that regulate apoptosis and cell cycle progression. Pim-1 has been shown to be overexpressed in a variety of cancers and has been implicated in human prostate tumorigenesis. The aim of our study was to clarify the role of Pim-1 during the prostate tumorigenesis and determine its potential as a molecular target for therapy. To accomplish this goal, we carried out a series of experiments using a genetically engineered mouse model of prostate cancer driven by the conditional inactivation of PTEN. High levels of Pim-1 were observed during the early stages of the tumorigenesis process which decreased as tumors progressed. Expression of Pim-1 was localized in the nucleus and cytoplasm of prostatic intraepithelial neoplasia (PIN), well-differentiated, and moderately-differentiated tumors. In poorly-differentiated tumors, Pim-1expression was heterogeneously expressed at lower levels and was predominantly localized to the cytoplasm of cancer cells. Levels of Pim-1 expression were increased in tumors from mice after surgical castration. To evaluate the therapeutic potential of Pim-1as a target for prostate cancer, we tested the antitumor effects of AZD1208, a highly potent Pim kinase inhibitor, on a panel of cell lines derived from castration-naïve and castration-resistant mouse prostate cancer. AZD1208 inhibited the tumor cell growth of several cell lines and demonstrated higher sensitivity to those derived from castration resistant tumors. In vivo, drug intervention studies show that treatment with AZD1208 reduced tumor growth of castration-naïve and castration-resistant prostate tumors by 12.1 (P = 0.162) and 24.3% (P<0.001), respectively. These findings provide further support for a role of Pim-1 during prostate tumorigenesis and could thus serve as a rational target for the development of novel combination strategies. Citation Format: Marco A. De Velasco, Takashi Oki, Yurie Kura, Naomi Ando, Emiko Fukushima, Barry R. Davies, Dennis Huszar, Yutaka Yamamoto, Yuji Hatanaka, Nobutaka Shimizu, Kazuhiro Yoshimura, Masahiro Nozawa, Kazuhiro Yoshikawa, Kazuto Nishio, Hirotsugu Uemura. Evaluation of Pim-1 kinase inhibition in a preclinical model of mouse prostate cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1850. doi:10.1158/1538-7445.AM2015-1850