Preclinical Models Of Prostate Cancer Research Articles

Development and translation of histotripsy

The aim of this article is to outline the initial development of histotripsy, a noninvasive image-guided focused ultrasound technology that mechanically homogenizes targeted tissues and to describe the results of preclinical translational research directed toward urologic applications. Histotripsy tissue ablation is based on initiation and control of acoustic cavitation at a target point within the body. This unique mechanical mechanism of action is distinct when compared with conventional thermal ablative modalities. Features of histotripsy (nonthermal, noninvasive, high precision, real-time monitoring/feedback, and tissue liquefaction) have prompted assessment of this technology as a potential ablative therapy for a number of organs and disease processes. Ongoing research efforts to apply histotripsy to preclinical models of benign prostatic hyperplasia, prostate cancer, renal masses, and renal calculi have resulted in enhanced understanding of cavitation bioeffects, refinement of treatment systems, strategies to enhance treatment efficiency, and initiation of a pilot human clinical trial to assess the safety of histotripsy for benign prostatic hyperplasia therapy.

Reappraisal of glucocorticoids in castrate-resistant prostate cancer.

Recent reports and discussions of preclinical prostate cancer models have emphasized the possibility that enzalutamide resistance may be mediated by glucocorticoid receptors (GR).12 In both in vitro and xenograft animal studies, it is possible to show that the GR is up-regulated in prostate cancer cell lines and that dexamethasone reverses enzalutamide induced growth inhibition. In these model systems, GR agonists can induce a subset of androgen receptor target genes including prostate-specific antigen. These investigators also report a correlation between GR expression in patient-derived prostate cancer specimens and clinical response to enzalutamide. The authors discuss the possibility that these findings have important clinical relevance. We note that the current clinical evidence for GR mediating drug resistance or disease progression in patients with castrate-resistant prostate cancer (CRPC) is very limited at best.

O10 CRM1-selective inhibitors of nuclear export (sine) reduce the incidence of tumor spreading and improve overall survival in preclinical models of prostate cancer

O10 CRM1-selective inhibitors of nuclear export (sine) reduce the incidence of tumor spreading and improve overall survival in preclinical models of prostate cancer

Effects of exercise training on tumor hypoxia and vascular function in the rodent preclinical orthotopic prostate cancer model

Regular physical exercise is considered to be an integral component of cancer care strategies. However, the effect of exercise training on tumor microvascular oxygenation, hypoxia, and vascular function, all of which can affect the tumor microenvironment, remains unknown. Using an orthotopic preclinical model of prostate cancer, we tested the hypotheses that, after exercise training, in the tumor, there would be an enhanced microvascular Po2, increased number of patent vessels, and reduced hypoxia. We also investigated tumor resistance artery contractile properties. Dunning R-3327 AT-1 tumor cells (10(4)) were injected into the ventral prostate of 4-5-mo-old male Copenhagen or Nude rats, which were randomly assigned to tumor-bearing exercise trained (TB-Ex trained; n = 15; treadmill exercise for 5-7 wk) or sedentary groups (TB-Sedentary; n = 12). Phosphorescence quenching was used to measure tumor microvascular Po2, and Hoechst-33342 and EF-5 were used to measure patent vessels and tumor hypoxia, respectively. Tumor resistance artery function was assessed in vitro using the isolated microvessel technique. Compared with sedentary counterparts, tumor microvascular Po2 increased ∼100% after exercise training (TB-Sedentary, 6.0 ± 0.3 vs. TB-Ex Trained, 12.2 ± 1.0 mmHg, P < 0.05). Exercise training did not affect the number of patent vessels but did significantly reduce tumor hypoxia in the conscious, resting condition from 39 ± 12% of the tumor area in TB-Sedentary to 4 ± 1% in TB-Ex Trained. Exercise training did not affect vessel contractile function. These results demonstrate that after exercise training, there is a large increase in the driving force of O2 from the tumor microcirculation, which likely contributes to the considerable reduction in tumor hypoxia. These results suggest that exercise training can modulate the microenvironment of the tumor, such that a sustained reduction in tumor hypoxia occurs, which may lead to a less aggressive phenotype and improve patient prognosis.

Combined Treatment Effects of Radiation and Immunotherapy: Studies in an Autochthonous Prostate Cancer Model

To optimize the combination of ionizing radiation and cellular immunotherapy using a preclinical autochthonous model of prostate cancer. Transgenic mice expressing a model antigen under a prostate-specific promoter were treated using a platform that integrates cone-beam CT imaging with 3-dimensional conformal therapy. Using this technology we investigated the immunologic and therapeutic effects of combining ionizing radiation with granulocyte/macrophage colony-stimulating factor-secreting cellular immunotherapy for prostate cancer in mice bearing autochthonous prostate tumors. The combination of ionizing radiation and immunotherapy resulted in a significant decrease in pathologic tumor grade and gross tumor bulk that was not evident with either single-modality therapy. Furthermore, combinatorial therapy resulted in improved overall survival in a preventive metastasis model and in the setting of established micrometastases. Mechanistically, combined therapy resulted in an increase of the ratio of effector-to-regulatory T cells for both CD4 and CD8 tumor-infiltrating lymphocytes. Our preclinical model establishes a potential role for the use of combined radiation-immunotherapy in locally advanced prostate cancer, which warrants further exploration in a clinical setting.

A Clinically Relevant Androgen Receptor Mutation Confers Resistance to Second-Generation Antiandrogens Enzalutamide and ARN-509

Despite the impressive clinical activity of the second-generation antiandrogens enzalutamide and ARN-509 in patients with prostate cancer, acquired resistance invariably emerges. To identify the molecular mechanisms underlying acquired resistance, we developed and characterized cell lines resistant to ARN-509 and enzalutamide. In a subset of cell lines, ARN-509 and enzalutamide exhibit agonist activity due to a missense mutation (F876L) in the ligand-binding domain of the androgen receptor (AR). AR F876L is sufficient to confer resistance to ARN-509 and enzalutamide in in vitro and in vivo models of castration-resistant prostate cancer (CRPC). Importantly, the AR F876L mutant is detected in plasma DNA from ARN-509-treated patients with progressive CRPC. Thus, selective outgrowth of AR F876L is a clinically relevant mechanism of second-generation antiandrogen resistance that can potentially be targeted with next-generation antiandrogens. A missense mutation in the ligand-binding domain of the androgen receptor F876L confers resistance to the second-generation antiandrogens enzalutamide and ARN-509 in preclinical models of AR function and prostate cancer and is detected in plasma DNA from ARN-509-treated patients with progressive disease. These results chart a new path for the discovery and development of next-generation antiandrogens that could be coupled with a blood-based companion diagnostic to guide treatment decisions.

Tasquinimod: A Novel Drug in Advanced Prostate Cancer

Tasquinimod, an oral quinolone-3-carboxamide with anti-tumor activity in preclinical models of prostate cancer, has been tested in patients with minimally symptomatic castration-resistant prostate cancer (CRPC), showing promising inhibitory effects on the occurrence of metastasis and delayed disease progression. Although its mode of action is not fully understood, tasquinimod presumably exerts its unique anti-tumor action through inhibition of angiogenesis and immunomodulation. In clinical studies, tasquinimod demonstrated anti-tumor activity in prostate cancer in combination with a mild-to-moderate side effect profile. With single-agent tasquinimod, dose-limiting toxicity was amylase elevation without signs of pancreatitis and sinus tachycardia. The maximum tolerated dose in Phase I studies in patients with CRPC was once daily administration of 0.5-1-mg tasquinimod orally. In a Phase II trial, significant clinical activity has been demonstrated in asymptomatic or minimally symptomatic, chemotherapy-naive, metastatic CRPC (mCRPC) patients. Men were randomized to tasquinimod or placebo in a 2:1 fashion; treatment with tasquinimod resulted in significant improvement of median progression-free survival (7.6 vs 3.3 months with placebo; p = 0.0042). Based on these encouraging effects, a randomized, double-blind, placebo-controlled trial in men with minimally symptomatic mCRPC has been designed. This large Phase III trial, powered for a primary end point of progression-free survival, has now enrolled the target number of 1200 men. If the Phase II data are validated in the Phase III trial a new compound with a unique mode of action might become approved as a future therapy for minimally symptomatic mCRPC patients.

Efficacy of oncolytic adenovirus expressing suicide genes and interleukin-12 in preclinical model of prostate cancer

Oncolytic adenovirus-mediated suicide gene therapy has been shown to improve local tumor control in preclinical tumor models and in the clinic. Although local tumor control is important, for most human cancers, new therapies must also target metastatic disease if they are to have an impact on survival. Here, we test the hypothesis that adding cytokine gene therapy to our multimodal platform improves both local and metastatic tumor control in a preclinical model of prostate cancer. An oncolytic adenovirus (Ad5-yCD/mutTKSR39rep-mIL12) expressing two suicide genes and mouse interleukin-12 (IL-12) was generated. Relative to an adenovirus lacking IL-12 (Ad5-yCD/mutTKSR39rep), Ad5-yCD/mutTKSR39rep-mIL12 improved local and metastatic tumor control in the TRAMP-C2 prostate adenocarcinoma model, resulting in a significant increase in survival. Ad5-yCD/mutTKSR39rep-mIL12 resulted in high levels of IL-12 and interferon gamma in serum and tumor, increased natural killer (NK) and cytotoxic T-lymphocyte lytic activities, and the development of tumor-specific antitumor immunity. Immune cell depletion studies indicated that both the innate and adaptive arms of immunity were required for maximal Ad5-yCD/mutTKSR39rep-mIL12 activity. The results demonstrate that the addition of IL-12 significantly improves the efficacy of oncolytic adenovirus-mediated suicide gene therapy and provide the scientific basis for future trials targeting locally aggressive cancers.

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 Jr.Gilberto de Castro Jr.Gilberto 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. 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 and quality of life studies. Dr Castro has more than 35 publications in peer-reviewed journals and he is also involved in cancer education, being a member of the European School of Oncology team of Discussants (e-ESO). 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. Ahmad AwadaAhmad AwadaProfessor Ahmad Awada studied Medicine at the Free University in Brussels (ULB), Belgium. He did a specialisation in Internal Medicine and Medical Oncology at Jules Bordet Institute (under the supervision of Professor Jean Klastersky), in Brussels, until 1992 (“La plus grande distinction”). During his specialisation, he also followed trainings in the clinical development of new therapies and new anticancer drugs, under the supervision of Professor Martine Piccart. To deepen his training, he stayed in the Netherlands (New Drug Development Office, Free University, Amsterdam) and in San Antonio, USA (Institute for Drug Development, under the direction of Professor D. Von Hoff). He focused on the clinical development of new anticancer agents. Back from the USA at the beginning of 1994, Doctor Awada became Assistant Head of Medical Oncology Clinic, and Head of the New Drugs Development Unit at Jules Bordet Institute, Brussels. Since April 2005, he is the Head of the Medical Oncology Clinic. In addition and from 1st March 2011, Dr Awada was hold Associate Head of Medicine Department. He has an important clinical activity in the treatment of solid tumors. Doctor Awada took an active part in the development of new anticancer drugs, some of them already widely used. Thanks to the recent progress in technology and computer sciences, and consequently in molecular biology, we can understand better now how a cancer cell works. Many drugs are now studied to block this process. Those are the molecular-targeted therapies, a subject studied extensively in clinical research by Doctor Awada and were the basis for this thesis obtained from the ULB, Brussels, in 2004. The aim of Doctor Awada, as far as research is concerned, is to look for new active anticancer drugs in solid tumors (new cytotoxics and molecular targeted therapies), and to individualize the treatments of cancer patients.

Abstract 3440: CRM1-Selective Inhibitors of Nuclear Export (SINE) reduce the incidence of tumor spreading and improve overall survival in preclinical models of prostate cancer.

Abstract Background: CRM1 (XPO1) is the exclusive exportin mediating transport of most tumor suppressor proteins (TSPs) including p53, pRb, FOXO, APC and p21 out of the nucleus, abrogating their function. Methods: We tested the effects of the potent, selective, clinical stage oral SINE compound KPT-330 in prostate cancer (PrCa) models. Male SCID mice orthotopically (intraprostatic) inoculated with the DU145 PrCa, known to produce highly metastatic tumors with visceral metastases. In parallel, male CD1-nu/nu mice were inoculated with intracardiac and intratibial injections of the aggressive/bone-derived PrCa PC3, known to produce prominent osteolytic bone lesions. The effects of SINEs KPT-330 and KPT-251 on metastatic spreading were determined. Results: We previously demonstrated that SINE CRM1 antagonists KPT330 and KPT251 have potent antitumor effects on PrCa both in vitro and in vivo. Here, we demonstrate that KPT-330 reduces intraprostatic DU145 tumor burden as well as the incidence of macroscopic metastases to lymph nodes, liver and lung, in a dose-dependent manner. The DU145 tumor burden was reduced by 41% with KPT-330 (4 mg/kg qd/5 days) and 61% (10 mg/kg q 3-4 d x 7) when compared to controls. The incidence of PC3-derived bone metastases were significantly reduced with KPT-330 at 10 mg/kg (q 2d x 3 weeks). At 50 days after cell injection, 80% (8/10) of controls and 0% (0/10) of the KPT-330-treated animals developed X-Ray evidence of bone lesions (p&amp;lt;0.05). The burden of bone metastases, measured by lytic bone area, was significantly higher in controls than in KPT-330-treated animals. Similarly, after intra-tibial injection, the lytic areas were higher in controls than in the KPT-330 group (p&amp;lt;0.05). The level of serum markers of osteoclast activity (TRAP and type I collagen fragment, CTX), was significantly higher in controls than in KPT-330-treated animals. The related SINE KPT-251 (100 mg/Kg q 2d x 3 weeks) confirmed the reduction of bone metastasis following CRM1 inhibition. The overall and disease free survival, evaluated at 170 days after tumor injection, were significantly higher in KPT-330- and KPT-251-treated animals versus controls (P&amp;lt; 0.0001). Treatment of PC3 and DU145 cells with KPT-330 lead to significant reductions in the secretion of proteolytic enzymes (MMP-9, MMP-2, uPA) as well as reduced ability of tumor cells to migrate and invade Matrigel. Impaired secretion of pro-angiogenic (VEGF, IL6, IL8) and pro-osteolytic (RANKL, IL6) cytokines was also observed. Conclusions: These data show that selective blockade of CRM1-dependent nuclear export has direct antitumor, anti-metastatic and anti-osteolytic activities in PrCa and thus represents a novel approach for the treatment of advanced/ metastatic PrCa. KPT-330 is now in Phase 1 clinical trials in patients with advanced solid tumors (clinicaltrailas.gov: NCT01607905). Citation Format: Giovanni Luca Gravina, Monica Tortoreto, Andrea Mancini, Paola Muzi, Luca Ventura, Sandra D'ascenzo, Alessandro Addis, Yosef Landesman, Dilara McCauley, Vincenza Dolo, Michael Kauffman, Sharon Shacham, Nadia Zaffaroni, Claudio Festuccia. CRM1-Selective Inhibitors of Nuclear Export (SINE) reduce the incidence of tumor spreading and improve overall survival in preclinical models of prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3440. doi:10.1158/1538-7445.AM2013-3440

Abstract LB-304: ATSP-9172, a novel Stapled Peptide inhibitor of HIF-dependent transcriptional activity with in vivo antitumor efficacy in a preclinical model of prostate cancer.

Abstract Hypoxia-inducible transcription factors (HIF) are key regulators of cellular adaptation to hypoxia in solid tumors, and HIF-1α controls the expression of genes involved in anaerobic metabolism, angiogenesis, cell growth and survival. Hydrocarbon cross-linked alpha helical peptides (Stapled Peptides) are a breakthrough approach to create new class of drugs that modulate intracellular protein-protein interactions. Here, we have mimicked the structure and function of the CITED2 protein, an endogenous negative regulator of the interaction between HIF-1α and p300 proteins, by designing a Stapled Peptide derived from CITED2 to generate the first example of a potent and selective Stapled Peptide inhibitor of HIF-1α-dependent transcription. ATSP-9172 bound to the CH1 domain of p300 and disrupted the HIF-1α C-TAD/CH1 interaction in biochemical assays and inhibited HIF-dependent reporter gene activity in ME-180 cells. Examination of endogenous transcript levels in ME-180 cells revealed that ATSP-9172 down-regulated the transcription of HIF-1α target genes, such as adolase C, angiopoietin-like 4, and carbonic anhydrase 9 in a dose-dependent manner, but did not affect the expression of non-HIF target genes, verifying a specific and on-target mechanism of action. ATSP-9172 exhibited a dramatic improvement in solubility and plasma stability profile relative to the linear peptide, and demonstrated favorable pharmacokinetic properties in mice by providing high systemic exposure, low plasma clearance and long elimination half-life. Finally, intravenous administration of ATSP-9172 on an every other day schedule significantly inhibited tumor growth in a PC-3 human prostate tumor xenograft model (p &amp;lt; 0.05); this inhibition was found to be dose-dependent. Our results demonstrate that a Stapled Peptide mimicking the HIF inhibitory function of the native CITED2 protein provides a novel and specific strategy to suppress HIF-1α-dependent gene expression for cancer therapy. Citation Format: Kaiming Sun, Steven J. DeMarco, Vincent Guerlavais, Aditi Mukherjee, Sean Irwin, Eric Shi, Hongliang Cai, Krzysztof Darlak, Solimar Santiago, Jessica Pero, Karen A. Olson, Huw M. Nash, Yong Chang. ATSP-9172, a novel Stapled Peptide inhibitor of HIF-dependent transcriptional activity with in vivo antitumor efficacy in a preclinical model of prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr LB-304. doi:10.1158/1538-7445.AM2013-LB-304

Abstract 320: New metastatic murine prostate cancer cell lines and preclinical model of human prostate cancer.

Abstract Defining oncogene-specific molecular pathways required for the induction and maintenance of prostate cancer is essential for the rational design of new therapies. Identifying molecular predictors of prostate cancer patient survival is important for patient therapeutic substratification. We generated murine prostate cancer cell lines via selective transduction with a single oncogene (c-Myc, Ha-Ras, NeuT, and v-Src). These cell lines demonstrate contact-independent growth characteristics in soft agar, and have the substantial growth advantage over primary prostate epithelial cells. Each of the prostate lines grew tumor in immune competent mice after subcutaneous injection, and develop lung metastasis in c-Myc, Ha-Ras, and v-Src cell line groups. RNA samples were prepared from the these cell lines, Microarray analysis identified a total of 2635 out of 22115 genes that were significantly altered in expression (at least two-fold change) in oncogene over-expressing cell lines when compared with prostate epithelial cell control samples. The distinct oncogene expression signature was compared to gene signatures obtained from other published databases to identify similarities to human prostate cancer phenotypes. Comparisons were performed against gene signatures representative of differential expression in advanced state vs. early stage prostate cancer, high grade vs low grade prostate cancer, recurrent vs. nonrecurrent, the results indicate a significant degree of similarity between the prostate oncogene expression signature and high-grade disease; between the oncogene expression signature and the advanced stage disease phenotype. Interrogation of two distinct cohorts of Prostate cancer patient samples using the oncogene signature demonstrated an ability to distinguish tumor from normal prostate with a predictive value for prostate cancer of 98 - 99%. The signature provided in blinded study independent substratification of reduced recurrence free survival by Kaplan-Meier analysis. The generation of new oncogene-specific prostate cancer cell lines that recapitulate human prostate cancer gene expression, that metastasize in immune-competent mice, are a valuable new resource for testing targeted therapy. The molecular signatures identified herein provide further value over current markers of prediction and outcome. Citation Format: Xiaoming Ju, Richard G. Pestell. New metastatic murine prostate cancer cell lines and preclinical model of human prostate cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 320. doi:10.1158/1538-7445.AM2013-320

494 MESENCHYMAL STEM CELL MEDIATED CANCER THERAPY INHIBITS TUMOR GROWTH IN THE TRANSGENIC ADENOCARCINOMA OF THE MOUSE PROSTATE (TRAMP) MODEL

INTRODUCTION AND OBJECTIVES: Vectors that home tumors and micrometastases may be a unique tool to activate drugs selectively within a cancer site. Mesenchymal stem cells (MSC) as vectors for the prodrug-activating enzyme cytosine deaminase::uracil phosphoribosyltransferase (CD) convert the nontoxic 5-fluorocytosine (5FC, prodrug) into the antitumor drug 5-fluorouracil. Conversion occurs within the tumor mass thanks to the innate ability of MSC to target tumor lesions. We previously demonstrated that CD-MSC are effective in inhibiting growth of prostate tumor grafts in mice. Our objective was to further evaluate this therapeutic strategy in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model that better mimics onset and progression of human prostate disease. METHODS: After ethical approval, human adipose tissue (AT) MSC and mouse bone marrow (BM) MSC were used as vectors for CD. TRAMP mice were employed as a preclinical prostate cancer model. Autochthonous tumor volume was measured by magnetic resonance imaging (MRI) performed on a 7T preclinical scanner with multiplanar high resolution T2-weighted. Images post-processing was performed on MIPAV 12.5 software. Two millions CD-AT-MSC (first treatment) and CD-BM-MSC (second treatment) were injected into the tail vein. Prodrug (300 mg/kg/day) was administered intraperitoneally for 7-10 days after delivery of therapeutic cells. Mann-Whitney U test was used for comparisons RESULTS: TRAMP mice (ca. 26 weeks old) were divided into the following groups: CONTROL (received CD-MSC alone or 5FC alone) and TREATED (received CD-MSC plus 5FC). In the CONTROL group not all animals reached the time of the second MRI (some mice were sacrificed before second MRI for ethical reasons). Before therapy median TV was 91.19 mm 14.9 for CONTROL mice (n 6) and 106.25 mm 19.24 for TREATED mice (n 7). After therapy median TV was 106.77 mm 21.59 for CONTROL mice and 83.86 mm 14.09 for TREATED mice. We could therefore observe a median TV increase by 16.18% for the CONTROL mice and a median TV decrease by 28.72% for the TREATED mice (p 0.05). CONCLUSIONS: Systemic administration of CD-AT-MSC and CD-BM-MSC and subsequent prodrug treatment inhibit autochthonous prostate tumor growth. If confirmed in future larger studies, specifically engineered MSC cells may offer a new strategy to improve efficacy and selectivity of current antitumor therapies.

PXD101 potentiates hormonal therapy and prevents the onset of castration-resistant phenotype modulating androgen receptor, HSP90, and CRM1 in preclinical models of prostate cancer

Aberrant activation or 'reactivation' of androgen receptor (AR) during androgen ablation therapy shows a potential cause for the development of castration-resistant prostate cancer. This study tested the hypothesis that PXD101, a potent pan histone deacetylase (HDAC) inhibitor, may prevent onset of castration-resistant phenotype and potentiate hormonal therapy. A panel of human prostate cancer cells with graded castration-resistant phenotype and in vivo models were used to verify this hypothesis. In this report, we demonstrated that hormonal manipulation favors the onset of castration-resistant phenotype increasing HDAC expression and activity as well as modulating expression and activity of AR, EGFR, HER2, and Akt. Consistent with these observations, the functional knockdown of HDACs by PXD101 prevented the onset of castration-resistant phenotype with a significant downregulation of AR, EGFR, HER2, and Akt expression/activity. The dysregulation of functional cooperation between HDAC6 with hsp90, on the one hand, and between GSK-3β with CRM1, on the other hand, may explain the biological effects of PXD101. In this regard, the HDAC6 silencing or the functional knockdown of hsp90 by 17AAG resulted in the selective downregulation of AR, EGFR, HER2, and Akt expression/activity, while the decreased phosphorylation of GSK-3β mediated by PXD101 increased the nuclear expression of CRM1, which in turn modified the AR and survivin recycling with increased caspase 3 activity. HDAC inhibitors retain the ability to prevent the onset of castration-resistant phenotype and, therefore, merit clinical investigation in this setting. However, additional data are needed to develop clinical treatment strategies for this disease stage.

Tasquinimod: A Novel Angiogenesis Inhibitor–Development in Prostate Cancer

Castration resistant prostate cancer (CRPC) treatment has been revolutionized over the past few years by the approval of novel therapies including cabazitaxel, sipuleucel-T, abiraterone and enzalutamide. Though androgen deprivation and chemotherapy remain the main therapeutic approaches for this disease, a series of targeted agents is also in development for the treatment of CRPC. Tasquinimod is a quinolone-3-carboxamide with antiangiogenic and antitumor activity in preclinical models of prostate cancer. A recent Phase II trial with this agent has demonstrated a significant clinical activity in asymptomatic or minimally symptomatic, chemotherapy-naïve, CRPC patients. A confirmatory Phase III trial of tasquinimod in prostate cancer is underway. Because of its antiangiogenic and immunomodulatory properties tasquinimod represents a novel targeted therapy with a unique mechanism of action.

Iodine Uptake and Prostate Cancer in the TRAMP Mouse Model

Iodine supplementation exerts antitumor effects in several types of cancer. Iodide (I⁻) and iodine (I₂) reduce cell proliferation and induce apoptosis in human prostate cancer cells (LNCaP and DU-145). Both chemical species decrease tumor growth in athymic mice xenografted with DU-145 cells. The aim of this study was to analyze the uptake and effects of iodine in a preclinical model of prostate cancer (transgenic adenocarcinoma of the mouse prostate [TRAMP] mice/SV40-TAG antigens), which develops cancer by 12 wks of age. ¹²⁵I⁻ and ¹²⁵I₂ uptake was analyzed in prostates from wild-type and TRAMP mice of 12 and 24 wks in the presence of perchlorate (inhibitor of the Na⁺/I⁻ symporter [NIS]). NIS expression was quantified by quantitative polymerase chain reaction (qPCR). Mice (6 wks old) were supplemented with 0.125 mg I⁻ plus 0.062 mg I₂/mouse/day for 12 or 24 wks. The weight of the genitourinary tract (GUT), the number of acini with lesions, cell proliferation (levels of proliferating cell nuclear antigen [PCNA] by immunohistochemistry), p53 and p21 expression (by qPCR) and apoptosis (relative amount of nucleosomes by enzyme-linked immunosorbent assay) were evaluated. In both age-groups, normal and tumoral prostates take up both forms of iodine, but only I⁻ uptake was blocked by perchlorate. Iodine supplementation prevented the overexpression of NIS in the TRAMP mice, but had no effect on the GUT weight, cell phenotype, proliferation or apoptosis. In TRAMP mice, iodine increased p53 expression but had no effect on p21 (a p53-dependent gene). Our data corroborate NIS involvement in I⁻ uptake and support the notion that another transporter mediates I₂ uptake. Iodine did not prevent cancer progression. This result could be explained by a strong inactivation of the p53 pathway by TAG antigens.

Nuclear Stat5a/b predicts early recurrence and prostate cancer–specific death in patients treated by radical prostatectomy

There is an urgent need for reliable markers to identify patients whose prostate cancer (PCa) will recur after initial therapy and progress to lethal disease. Gleason score (GS) is considered the most accurate predictive marker for disease-specific mortality after primary treatment of localized PCa. Most PCas cluster into groups of GS 6 and 7 with considerable variation in the disease recurrence and disease-specific death. In preclinical PCa models, Stat5a/b promotes PCa growth and progression. Stat5a/b is critical for PCa cell viability in vitro and for tumor growth in vivo and promotes metastatic dissemination of cancer in nude mice. Here, we analyzed the predictive value of high nuclear Stat5a/b protein levels in 2 cohorts of PCas: Material I (n = 562) PCas treated by radical prostatectomy (RP), and Material II (n = 106) PCas treated by deferred palliative therapy. In intermediate GS PCas treated by radical prostatectomy, high levels of nuclear Stat5a/b predicted both early recurrence (univariable analysis; P < .0001, multivariable analysis; HR = 1.82, P = .017) and early PCa-specific death (univariable analysis; P = .028). In addition, high nuclear Stat5a/b predicted early disease recurrence in both univariable (P < .0001) and multivariable (HR = 1.61; P = .012) analysis in the entire cohort of patients treated by RP regardless of the GS. Patients treated by deferred palliative therapy, elevated nuclear Stat5a/b expression was associated with early PCa-specific death by univariable Cox regression analysis (HR = 1.59; 95% CI = [1.04, 2.44]; P = .034). If confirmed in future prospective studies, nuclear Stat5a/b may become a useful independent predictive marker of recurrence of lethal PCa after RP for intermediate GS PCas.

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 CastroGilberto de CastroGilberto 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. 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 and quality of life studies. Dr Castro has more than 25 publications in peer-reviewed journals and he is also involved in cancer education, being a member of the European School of Oncology team of Discussants (e-ESO). 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. Ahmad AwadaAhmad AwadaProfessor Ahmad Awada was born in Lebanon and studied Medicine at the Free University in Brussels (ULB), Belgium. He did a specialisation in Internal Medicine and Medical Oncology at Jules Bordet Institute (under the supervision of Professor Jean Klastersky), in Brussels, until 1992 (“La plus grande distinction”). During his specialisation, he completed training in the clinical development of new therapies and new anticancer drugs, under the supervision of Professor Martine Piccart. To further his training, he stayed in the Netherlands (New Drug Development Office, Free University, Amsterdam) and in San Antonio, USA (Institute for Drug Development, under the direction of Professor D. Von Hoff). He focused on the clinical development of new anticancer agents. Back from the USA at the beginning of 1994, Professor Awada became Assistant Head of Medical Oncology Clinic, and Head of the New Drugs Development Unit at Jules Bordet Institute, Brussels. Since April 2005, he is the Head of the Medical Oncology Clinic. He has an important clinical activity in the treatment of solid tumors and in particular head & neck cancers. Doctor Awada took an active part in the development of new drugs, some of them already widely used. Thanks to the recent progress in technology and computer sciences, and consequently in molecular biology, we can understand better now how a cancer cell works and how it becomes a cancer cell. Many drugs are now studied to block this process. Those are the molecular-targeted therapies, a subject studied extensively in clinical research by Professor Awada and were the basis for his thesis obtained from the ULB, Brussels, in 2004. Professor Awada's research aims to look for new active anticancer drugs in solid tumors (new cytotoxics and molecular targeted therapies), and to individualize the treatments according to the tumor characteristics.

Abstract 2755: Enhanced anti-tumor effects using a combinatorial targeted treatment strategy in a preclinical model of prostate cancer

Abstract Recently developed strategies use molecular targeting agents specifically designed to target core regulatory signaling pathways of prostate cancers. Growth factors mediate such signaling pathways that include the PI3K/Akt/PTEN/mTOR and Ras/Raf/MEK/MAPK as well as other essential pathways. However various mitigating factors such a genetic variation, molecular diversity, diverging and converging of signaling pathways make it improbable that treatment with any single agent will result in any long-term enhanced tumor. To overcome such problems we investigated the toxicity and antitumor effects of combined targeted therapy with the mTOR inhibitor everolimus and the mulitkinase inhibitor sorafenib in a prostate-specific PTEN conditional knockout mouse model of human prostate cancer. Non-castrated and castrated (castrate-resistant prostate cancer model, CRPC) PSACre;PTENloxP/loxP mutant mice, harboring prostate tumors, were treated with everolimus and sorafenib alone or in combination for 4 weeks beginning at 16 weeks of age. All mice appeared healthy and there were no significant differences in body weights, appearance or histological findings between treatment and control groups at the end of the experiment. Our analysis shows that combination therapy has a significant additive inhibitory effect on tumor growth in non-castrate prostate cancer model (8.8 mm2, 7.7 mm2, 7.1 mm2 and 5.2 mm2 in control, everolimus, sorafenib and combination treatment groups, respectively, p=0.005). Ki67 expression was decreased and positive TUNEL apoptotic bodies was increased in combination treatment groups compared to everolimus and sorafenib monotherapy in both non-castrated and CRPC treatment groups. We also show that combination therapy, but not monotherapy, cooperated to inhibit phosphorylation of the eukaryotic translation initiation factor 4B (eIF4B). Our study provides preclinical evidence that a targeted combination treatment strategy with everolimus and sorafenib is tolerable and leads to improved treatment efficacy over single agent therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2755. doi:1538-7445.AM2012-2755

Abstract 2340: CPS49 and Flavopiridol: a new selective drug combination for advanced prostate cancer

Abstract Prostate cancer (PCa) still ranks as the second most commonly diagnosed cancer and metastatic castration-resistant prostate cancer (CRPC) is a leading cause of cancer death in men around the world. The common treatment for patients with CRPC is chemotherapy based on docetaxel. While there are currently seven agents approved for CRPC and four regimens have shown some survival benefit, those survival prolongations have been modest and unfortunately all patients will eventually progress. Thus, there is a need for new agents and regimens for this disease. 2-(2,4-Difluoro-phenyl)-4,5,6,7-tetrafluoro-1H-isoindole-1,3(2H)-dione (CPS49) is a member of a class of redox-reactive thalidomide analogs that show selective killing of leukemic cells by increasing intracellular reactive oxygen species (ROS) and targeting multiple transcriptional pathways. Flavopiridol is a semisynthetic flavonoid that inhibits cyclin dependent kinases and also provokes lethality against leukemic cells. We previously found that CPS49 and flavopiridol combination induced selective cytotoxicity associated with mitochondrial dysfunction and elevations of ROS in leukemic cells ranging from additive to synergistic activity at low micromolar concentrations. The goal of this study was to investigate the selectivity and efficacy of CPS49-flavopiridol combination in prostate cancer preclinical models. Our results showed that flavopiridol enhanced CPS49 cytotoxicity in all human prostate tumor cell lines analyzed (PC3, C4-2, LNCaP and 22RV1); however non tumor cell lines (293HEK and MCF10) were resistant to the tested doses. Furthermore, it was previously reported, high doses of flavopiridol (10 μM) or CPS49 (12 μM) were needed to inhibit tumor growth in PC3 xenograft mice compared with vehicle treated mice. Here, we demonstrated that combining these two agents, antitumor activity was synergistically enhanced with low doses. Injecting subcutaneously PC3 cells in nu/nu mice, we found that CPS49-flavopiridol administration reduced tumor volume approximately 83% after 2 weeks of co-treatment and 54% after 1 week of low dose flavopiridol pretreatment and 2 weeks of drug combination. In addition, we performed RT-qPCR array containing 26 genes from PC3 cells exposed to CPS49 and flavopiridol combination. We determined that this treatment shut down the expression of several genes involved in cell cycle, DNA damage and tumor progression. Histological analysis of xenograft PC3 tumor samples showed extensive areas of necrosis induced by the treatment. Furthermore, we assessed the efficacy of CPS49 in combination with paclitaxel (docetaxel analog). All the prostate tumor cell lines tested were highly sensitive to this combination. However, this combination did not reduce the tumor volume in PC3 xenografts. These results indicate that the CPS49 and flavopiridol is a promising new alternative for the treatment of CRPC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2340. doi:1538-7445.AM2012-2340