Androgen-dependent Human Prostate Cancer Cell Research Articles

Follicle-stimulating hormone promotes growth of human prostate cancer cell line-derived tumor xenografts.

Chemical castration in prostate cancer can be achieved with gonadotropin-releasing hormone (GnRH) agonists or antagonists. Their effects differ by the initial flare of gonadotropin and testosterone secretion with agonists and the immediate pituitary-testicular suppression by antagonists. While both suppress luteinizing hormone (LH) and follicle-stimulating hormone (FSH) initially, a rebound in FSH levels occurs during agonist treatment. This rebound is potentially harmful, taken the expression of FSH receptors (R) in prostate cancer tissue. We herein assessed the role of FSH in promoting the growth of androgen-independent (PC-3, DU145) and androgen-dependent (VCaP) human prostate cancer cell line xenografts in nude mice. Gonadotropins were suppressed with the GnRH antagonist degarelix, and effects of add-back human recombinant FSH were assessed on tumor growth. All tumors expressed GnRHR and FSHR, and degarelix treatment suppressed their growth. FSH supplementation reversed the degarelix-evoked suppression of PC-3 tumors, both in preventive (degarelix and FSH treatment started upon cell inoculation) and therapeutic (treatments initiated 3weeks after cell inoculation) setting. A less marked, though significant FSH effect occurred in DU145, but not in VCaP xenografts. FSHR expression in the xenografts supports direct FSH stimulation of tumor growth. Testosterone supplementation, to maintain the VCaP xenografts, apparently masked the FSH effect on their growth. Treatment with the LH analogue hCG did not affect PC-3 tumor growth despite their expression of luteinizing hormone/choriongonadotropin receptor. In conclusion, FSH, but not LH, may directly stimulate the growth of androgen-independent prostate cancer, suggesting that persistent FSH suppression upon GnRH antagonist treatment offers a therapeutic advantage over agonist.

Effect of propofol on androgen receptor activity in prostate cancer cells

Androgen receptor is a nuclear receptor and transcription factor activated by androgenic hormones. Androgen receptor activity plays a pivotal role in the development and progression of prostate cancer. Although accumulating evidence suggests that general anesthetics, including opioids, affect cancer cell growth and impact patient prognosis, the effect of those drugs on androgen receptor in prostate cancer is not clear. The purpose of this study was to investigate the effect of the general anesthetic propofol on androgen receptor activity in prostate cancer cells. An androgen-dependent human prostate cancer cell line (LNCaP) was stimulated with dihydrotestosterone (DHT) and exposed to propofol. The induction of androgen receptor target genes was investigated using real-time reverse transcription polymerase chain reaction, and androgen receptor protein levels and localization patterns were analyzed using immunoblotting and immunofluorescence assays. The effect of propofol on the proliferation of LNCaP cells was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Propofol significantly inhibited DHT-induced expression of androgen receptor target genes in a dose- and time-dependent manner, and immunoblotting and immunofluorescence assays indicated that propofol suppressed nuclear levels of androgen receptor proteins. Exposure to propofol for 24h suppressed the proliferation of LNCaP cells, whereas 4h of exposure did not exert significant effects. Together, our results indicate that propofol suppresses nuclear androgen receptor protein levels, and inhibits androgen receptor transcriptional activity and proliferation in LNCaP cells.

The role of mesenchymal stem cells in promoting the transformation of androgen-dependent human prostate cancer cells into androgen-independent manner.

Mesenchymal stem cells (MSCs) play an important role in the development of human prostate cancer (PCa). However, the role of MSCs in the transformation of androgen-dependent human PCa cells into androgen-independent manner has been poorly understood. In this study, we investigated the underlying mechanism of MSCs in promoting PCa cells from androgen-dependent into androgen-independent manner. Firstly, we demonstrated that MSCs could affect the transformation of androgen-dependent human PCa cells into androgen-independent manner in vivo and in vitro. Then we found a substantial expression of TGF-β in MSCs. TGF-β blockade could significantly inhibit the promotive function of MSCs in PCa cells. Besides that, we also demonstrated androgen might inhibit the expression of TGF-β in MSCs. Furthermore, we found that either overexpression of SSEA-4 or the number of SSEA-4 positive MSCs in PCa tissues was associated with a shorter cancer-free survival interval (CFSI) and a worse overall survival (OS). Our results suggest that androgen blockade treatment in clinical PCa therapy may elicit the expression of TGF-β in MSCs, which will result in the transformation of androgen-dependent human PCa cells into androgen-independent manner.

Phase 1/2a, open-label, dose-escalation and safety study of APC-100 in men with advanced prostate cancer.

234 Background: Normal human prostate epithelium and prostate carcinoma exhibit high levels of oxidative stress, which is thought to play a role in the pathogenesis of prostate cancer. APC-100 (2,2,5,7,8-Pentamethyl-6-chromanol) is an oxidative stress modulator that reduces reactive oxygen species (ROS) in prostate cancer cells and inhibits growth of cultured androgen-dependent and independent human prostate cancer cells. We aimed to determine the maximum tolerated dose (MTD), dose-limiting toxicities (DLT), adverse events (AEs), clinical activity and pharmacokinetic (PK) parameters of APC-100 in men with castrate-resistant prostate cancer (CRPC). Methods: This open label phase 1/2a study utilizes a time-to-event reassessment method (TITE-CRM) design. Patients (pts) in cohorts of 3 were treated with escalating doses of APC-100 (900mg-2400mg) orally once daily continuously in 150 mg capsules. Cycles were 28 days. All patients were evaluable with PSAs and imaging studies. Results: Twenty pts (median age 72 [range 54-87]) with metastatic and non-metastatic CRPC were enrolled in the dose escalation cohort. Pts remained on study for a median of 12 weeks (range 4-36) and received therapy for a median of 3 cycles (range 1-9). One possible DLT (elevated ALT) was seen at dose level 1 and the patient was taken off study. No other DLTs at least possibly related to therapy were seen and no dose reductions were required. Most frequent AEs at least possibly related to therapy included nausea (grade 1 in 6 pts) and elevated transaminases (grade 1-3 in 5 patients). After enrolment of 20 pts the MTD was not reached, however the maximal feasible dose was exceeded due to the number of capsules required. Five of the 20 patients had stable disease per PSA and/or RECIST 1.1 as their best response. The median progression free survival (PFS) for the cohort was 2.8 months (range 1-8). Conclusions: APC-100 appears to be well tolerated with the MTD not reached. Limited PK assessment supports the need for alternative formulation to allow dose escalation to doses necessary to achieve exposures required for response. Once MTD is established, future studies will explore the activity of APC-100 as a therapeutic and chemopreventive intervention. Clinical trial information: NCT01436214.

Cytotoxicity of obacunone and obacunone glucoside in human prostate cancer cells involves Akt-mediated programmed cell death.

Obacunone and obacunone glucoside (OG) are naturally occurring triterpenoids commonly found in citrus and other plants of the Rutaceae family. The current study reports the mechanism of cytotoxicity of citrus-derived obacunone and OG on human androgen-dependent prostate cancer LNCaP cells. Both limonoids exhibited time- and dose-dependent inhibition of cell proliferation, with more than 60% inhibition of cell viability at 100 μM, after 24 and 48 h. Analysis of fragmentation of DNA, activity of caspase-3, and cytosolic cytochrome-c in the cells treated with limonoids provided evidence for activation of programmed cell death by limonoids. Treatment of LNCaP cells with obacunone and OG resulted in dose-dependent changes in expression of proteins responsible for the induction of programmed cell death through the intrinsic pathway and down-regulation of Akt, a key molecule in cell signaling pathways. In addition, obacunone and OG also negatively regulated an inflammation-associated transcription factor, androgen receptor, and prostate-specific antigen, and activated proteins related to the cell cycle, confirming the ability of limonoids to induce cytotoxicity through multiple pathways. The results of this study provided, for the first time, an evidence of the cytotoxicity of obacunone and OG in androgen-dependent human prostate cancer cells.

Abstract 3312: The antibiotic salinomycin cotargets two pivotal pathways in prostate cancer

Abstract Background: The androgen receptor (AR) and PI3K/AKT/mTOR signaling axis are two key pathways that are activated in prostate cancer (PC). Although interference with the AR axis is the common first-line treatment for controlling metastatic recurrent PC, fast-growing PC progresses rapidly on hormone therapy and chemotherapy to a terminal condition within 18 to 24 months. Inhibitors of the PI3K/AKT/mTOR axis, such as rapamycin and the dual inhibitor BEZ-235 (Novartis), are ineffective in treating metastatic PC in part due to feedback regulations that activate the AR axis. Reciprocally, inhibition of AR activity reduces the expression of an AKT phosphatase, which is an AR target gene, with consequent increase of the AKT kinase activity. The antibiotic salinomycin, a product of the bacterium Streptomyces albus, has known anti-neoplastic activity, and in a screen of 16,000 small molecules, salinomycin was found to be the most potent in causing apoptosis of breast cancer stem cells. We previously reported that salinomycin treatment elevated intracellular oxidative stress and induced growth arrest of PC cells due to apoptosis. Design and Results: Here we report further elaboration of the underlying mechanism for growth arrest of androgen-dependent (LNCaP) and castration-resistant (C4-2B) human prostate cancer cells by salinomycin at sub-micromolar concentrations. We report that salinomycin can significantly reduce mTOR activity in both LNCaP and C4-2B cells without altering the mTOR activity of non-malignant RWPE-1 prostate epithelial cells. The specificity of the salinomycin effect is evidenced by the result that other anti-cancer agents such as docetaxel, the plant lignan deoxypodophyllotoxin and vitamin D did not alter mTOR activity. Preliminary results suggest that salinomycin may also induce autophagy in PC cells. Importantly, AR expression was markedly reduced in salinomycin-treated prostate cancer cells, suggesting dual targeting of the AR pathway and PI3K/AKT/mTOR axis by this antibiotic. Conclusion: We conclude that salinomycin targets two pivotal pathways that promote prostate cancer progression. Unlike other PI3K/AKT/mTOR inhibitors, the AR-activating feedback cross regulation did not compromise the therapeutic potential of salinomycin. Salinomycin-targeted interventions of the survival signals for castration-resistant PC will further avoid chemotherapy-induced toxicity. Preclinical validation of our results will pave the way for testing the efficacy of salinomycin against prostate cancer in a clinical setting. Supported by a Merit-Review grant from the Department of Veterans Affairs. Citation Format: Nooshin Mirkheshti, Chung Song, Bandana Chatterjee. The antibiotic salinomycin cotargets two pivotal pathways in prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3312. doi:10.1158/1538-7445.AM2014-3312

Antischistosomal versus Antiandrogenic Properties of Aryl Hydantoin Ro 13-3978

In the early 1980s, the antischistosomal aryl hydantoin Ro 13-3978 (AH01), a close structural analogue of the androgen receptor antagonist nilutamide, was discovered. Administration of 100 mg/kg oral doses of AH01 to mice infected with adult and juvenile Schistosoma mansoni produced 95% and 64% total worm burden reductions, confirming its high activity against adult worms, and showing that AH01 is also effective against juvenile infections. AH01 had no measureable interaction with the androgen receptor in a ligand competition assay, but it did block dihydrotestosterone-induced cell proliferation in an androgen-dependent human prostate cancer cell line. For AH01, nilutamide, and three closely related aryl hydantoin derivatives, there was no correlation between antischistosomal activity and androgen receptor interaction.

Abstract 1069: Vav3 enhances androgen receptor splice variant activity and is critical for castration resistant prostate cancer growth and survival.

Abstract Advanced or metastatic prostate cancer is treated by androgen deprivation; however, patients inevitably relapse with castration resistant prostate cancer (CRPC) that grows independently of androgen. However, CRPC remains dependent on androgen receptor (AR) signaling, which includes constitutive, ligand–independent action of naturally occurring AR splice variants. For example, the AR splice variant AR3 (also termed AR–V7) is expressed in CRPC and is linked to poor prognosis. Vav3, a Rho GTPase guanine nucleotide exchange factor, is an AR coactivator that is up–regulated in human prostate cancer as compared to benign tissue as well as in pre–clinical models of CRPC. Vav3 confers castration–resistant growth to androgen–dependent human prostate cancer cells and increased expression has been linked to increased clinical biochemical relapse. Despite the importance of AR coactivators in promoting CRPC, the potential role of these regulatory proteins in modulating AR splice variant activity is unknown. We examined the contributions of Vav3 to AR activity in two CRPC cell lines that naturally express relatively high levels of Vav3 and AR3. Vav3 or AR3 knockdown greatly attenuated cell proliferation, soft agar growth and ligand–independent AR activity. Vav3 potently enhanced the transcriptional activity of AR3 and another clinically relevant AR splice variant ARv567es. Furthermore, Vav3 enhanced AR splice variant activity through a distinctly different mechanism than Vav3 coactivation of full length AR. Vav3 knockdown resulted in lowered nuclear AR3 levels while total AR3 protein and mRNA levels remained static. Conversely, overexpression of Vav3 resulted in increased nuclear AR3. Co–immunoprecipitation revealed that AR3 and Vav3 interact. These novel data demonstrating physical and functional interactions between Vav3, a unique AR coactivator, and an AR splice variant provide insights into the mechanisms by which Vav3 exploits and enhances AR signaling in the progression to CRPC. Citation Format: Stephanie Peacock, Cale D. Fahrenholtz, Kerry L. Burnstein. Vav3 enhances androgen receptor splice variant activity and is critical for castration resistant prostate cancer growth and survival. [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 1069. doi:10.1158/1538-7445.AM2013-1069

Effect of Serenoa repens (Permixon®) on the expression of inflammation-related genes: analysis in primary cell cultures of human prostate carcinoma

BackgroundTo analyze the expression at basal level of inflammation-related cytokines and chemokines and the activation status of the NF-κB pathway, together with the proliferation and apoptosis indexes in two widely used in vitro tumor models, the androgen-dependent human Prostate Cancer (PC) cell line LNCaP and the androgen-independent PC3 , and in primary cultures of human PC cells. To assess in these models and primary cultures, the effects of Serenoa repens (LSESr, Permixon®) on proliferation/apoptosis ratio, inflammation-related genes expression and NF-κB pathway activation.MethodsThe expression of IL-6, CCL-5, CCL-2, COX-1, COX-2, iNOS inflammation-related genes has been evaluated at the mRNA level in two in vitro human PC models (LNCaP and PC3 cell lines) and in 40 independent human prostatic primary cultures obtained from PC patients undergoing radical prostatectomy. Tissue fragments were collected from both PC lesions and normal hyperplastic tissue counterparts for each case. All cultures were treated with two different amounts of Permixon® (44 and 88 μg/ml) for different time points (16, 24, 48 and 72 hours), depending on the cell type and the assay; the expression of inflammation-related genes, cell growth (proliferation/apoptosis ratio) and NF-κB activation has been analyzed in treated and untreated cells by means of semi-quantitative RNA-PCR, cell proliferation and immunofluorescence respectively.ResultsWe detected a significant reduction (p <0.001) in PC and normal cells proliferation due to Permixon ® treatment. This result was related to an increase of the apoptotic activity showed by an increase in the number of anti-caspase-3 fluorescent cells. Almost all the inflammation-related genes (IL-6, CCL-5, CCL-2, COX-2 and iNOS) were expressed at the basal level in in vitro cultured cells and primary cultures and down-regulated by Permixon® treatment. This treatment interfered with NF-kB activation, detecting by the translocation of more than 30% of NF-κB p65 subunit to the nucleus.ConclusionsThe present study confirms the expression of inflammatory pattern in PC. We showed the effect of Permixon® on down-regulation of inflammatory-related genes in cell lines and in primary cultures. The inhibitory effect of Permixon® on cell growth could be partly associated to the down-regulation of inflammatory-related genes and to the activation of NF-κB pathway in prostate tissue.

Ansprechen auf eine Docetaxel-therapie im LNCaP-Prostata-karzinom-Xenograft-Mausmodell

SummaryThe aim of this study was to determine whether [11C]choline can be used for docetaxel therapy response assessment in a LNCaPprostate cancer xenograft mouse model using [11C]choline small-animal PET/CT. Animals, methods: The androgen-dependent human prostate cancer cell line LNCaP was implanted subcutaneously into the left flanks of 17 SCID-mice, 12.5 mg testosterone platelets were implanted in the neck wrinkle. All mice were injected 4–6 weeks after xenograft implantation with 37 MBq [11C]choline via the tail vein. Dynamic imaging was performed for 60 minutes with a small-animal PET/CT scanner. After the first [11C]choline PET/CT imaging 8 mice were subsequently injected intravenously with docetaxel twice (days 1 and 5) at a dose of 3 mg/kg body weight. 8 mice were treated with PBS as a control. [11C]choline PET/CT imaging was performed on day 7, 14 and 21 after treatment. Image analysis was performed using tumor/ muscle (T/M) ratios (ROIT/ROIM = T/M ratio). Results: All LNCaP tumours could be visualized by [11C]choline PET/CT. Before treatment the mean T/M ratio was 2.0 ± 0.2 in the docetaxel-treated group and 1.9 ± 0.2 in the control group (p = 0.837). There was a reduction in the mean [11C]choline uptake after docetaxel treatment of the tumours of the LNCaP cell line as early as 1 week after initiation of therapy (T/Mmean ratio 1.5 ± 0.2 after one week, 1.3 ± 0.2 after 2 weeks and 1.4 ± 0.2 after 3 weeks). There was no decrease in [11C]choline uptake in the control group. Conclusion: Our results show that [11C]choline has the potential for use in the early monitoring of the therapeutic effect of docetaxel in a LNCaP prostate cancer xenograft animal model.

Vav3 Enhances Androgen Receptor Splice Variant Activity and Is Critical for Castration-Resistant Prostate Cancer Growth and Survival

Advanced or metastatic prostate cancer is treated by androgen deprivation; however, patients inevitably relapse with castration-resistant prostate cancer (CRPC). CRPC remains dependent on androgen receptor (AR) signaling, which may include constitutive, ligand-independent action of naturally occurring AR splice variants. For example, the AR splice variant AR3 (also termed AR-V7) is expressed in CRPC and is linked to poor prognosis. Vav3, a Rho GTPase guanine nucleotide exchange factor, is an AR coactivator that is up-regulated in human prostate cancer compared with benign tissue and in preclinical models of CRPC. Vav3 confers castration-resistant growth to androgen-dependent human prostate cancer cells. Despite the importance of AR coactivators in promoting CRPC, the potential role of these regulatory proteins in modulating AR splice variant activity is unknown. We examined the contributions of Vav3 to AR activity in two CRPC cell lines that naturally express relatively high levels of Vav3 and AR3. Vav3 or AR3 knockdown greatly attenuated cell proliferation, soft agar growth, and ligand-independent AR activity. Vav3 potently enhanced the transcriptional activity of AR3 and another clinically relevant AR splice variant, ARv567es. Vav3 knockdown resulted in lowered nuclear AR3 levels, whereas total AR3 levels remained similar. Conversely, overexpression of Vav3 resulted in increased nuclear AR3. Coimmunoprecipitation revealed that AR3 and Vav3 interact. These novel data demonstrating physical and functional interactions between Vav3, a unique AR coactivator, and an AR splice variant provide insights into the mechanisms by which Vav3 exploits and enhances AR signaling in the progression to CRPC.

Abstract 2407: Snail 1 regulates invasion through uPA-uPAR and MMP-9 signaling in prostate cancer cells

Abstract Epithelial-mesenchymal transition (EMT) is a process by which cancer cells acquire mesenchymal properties, such as induction of N-cadherin, while epithelial-associated genes like E-cadherin are lost. This enables the cells to be more invasive, migratory and metastatic. Factors that can induce EMT include growth factors like transforming growth factor -α (TGF-β) and epidermal growth factor (EGF), and transcription factors like Snail1. Snail1-induced EMT promotes migration and invasion and we hypothesized that this may be mediated by urokinase (uPA) and its receptor (uPAR) activities. uPA, a serine protease, may be activated by integrin engagement to bind to its receptor, uPAR, and initiate a signaling cascade that regulates a variety of biological pathways including invasion. Since Snail1 can induce matrix metalloproteinases (MMP 2 and 9) which are also involved in cell invasion, we also examined MMP activity. Androgen-dependent LNCaP, and 22Rv1 and androgen-independent ARCaP human prostate cancer (PC) cells were stably transfected with empty vector control (Neo) or constitutively active Snail1 which led to increased cell migration and invasion. The levels of Snail1, uPA, and uPAR were measured by Western Blot analysis. uPA activity in conditioned media was measured using the Elisa uPA activity assay kit. Additionally, cells were treated with MAPK inhibitor, UO126, at set time points. Gelatin zymography analysis was utilized to detect MMP-9 activity in the conditioned media. Currently, ARCaP-Snail cells are being transiently transfected with uPAR siRNA to assay for the effects of uPAR knockdown on uPA and MMP activity. The data suggests that overexpression of Snail1 increased uPA and uPAR protein levels, while uPA activity was elevated in conditioned media from LNCaP, 22Rv1 and ARCaP cells. Also, MAPK inhibited MAPK expression in the cell and decreased uPA activity. In addition gelatin zymography showed higher MMP 9 activity in ARCaP-Snail overexpressing cells that was inhibited by MAPK inhibitor. Therefore, Snail-mediated cell migration and invasion in human prostate cancer cells may occur via the regulation of uPA and uPAR activities in addition to MMPs. 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 2407. doi:1538-7445.AM2012-2407

Polyphenols in brewed green tea inhibit prostate tumor xenograft growth by localizing to the tumor and decreasing oxidative stress and angiogenesis

It has been demonstrated in various animal models that the oral administration of green tea (GT) extracts in drinking water can inhibit tumor growth, but the effects of brewed GT on factors promoting tumor growth, including oxidant damage of DNA and protein, angiogenesis and DNA methylation, have not been tested in an animal model. To explore these potential mechanisms, brewed GT was administered instead of drinking water to male severe combined immunodeficiency (SCID) mice with androgen-dependent human LAPC4 prostate cancer cell subcutaneous xenografts. Tumor volume was decreased significantly in mice consuming GT, and tumor size was significantly correlated with GT polyphenol (GTP) content in tumor tissue. There was a significant reduction in hypoxia-inducible factor 1-alpha and vascular endothelial growth factor protein expression. GT consumption significantly reduced oxidative DNA and protein damage in tumor tissue as determined by 8-hydroxydeoxyguanosine/deoxyguanosine ratio and protein carbonyl assay, respectively. Methylation is known to inhibit antioxidative enzymes such as glutathione S-transferase pi to permit reactive oxygen species promotion of tumor growth. GT inhibited tumor 5-cytosine DNA methyltransferase 1 mRNA and protein expression significantly, which may contribute to the inhibition of tumor growth by reactivation of antioxidative enzymes. This study advances our understanding of tumor growth inhibition by brewed GT in an animal model by demonstrating tissue localization of GTPs in correlation with inhibition of tumor growth. Our results suggest that the inhibition of tumor growth is due to GTP-mediated inhibition of oxidative stress and angiogenesis in the LAPC4 xenograft prostate tumor in SCID mice.

A novel nuclear role for the Vav3 nucleotide exchange factor in androgen receptor coactivation in prostate cancer

Increased androgen receptor (AR) transcriptional activity mediated by coactivator proteins may drive castration resistant prostate cancer (CRPC) growth. Vav3, a Rho GTPase guanine nucleotide exchange factor (GEF), is over-expressed in human prostate cancers particularly in models of CRPC progression. Vav3 coactivates AR in a Vav3 pleckstrin homology (PH) domain-dependent but GEF-independent manner. Ectopic expression of Vav3 in androgen-dependent human prostate cancer cells conferred robust castration resistant xenograft tumor growth. Vav3 but not a Vav3 PH mutant greatly stimulated interaction between the AR amino and carboxyl termini (N-C interaction), which is required for maximal receptor transcriptional activity. Vav3 was distributed between the cytoplasm and nucleus with nuclear localization dependent upon the Vav3 PH domain. Membrane targeting of Vav3 abolished Vav3 potentiation of AR activity; whereas, nuclear targeting of a Vav3 PH mutant rescued AR coactivation suggesting that nuclear localization is a key function of the Vav3 PH domain. A nuclear role for Vav3 was further demonstrated by sequential chromatin immunoprecipitation assays, which revealed that Vav3 and AR were recruited to the same transcriptional complexes of an AR target gene enhancer. These data demonstrate the importance of Vav3 in CRPC and define a novel nuclear function of Vav3 in regulating AR activity.

Monoacylglycerol Lipase Exerts Dual Control over Endocannabinoid and Fatty Acid Pathways to Support Prostate Cancer

Cancer cells couple heightened lipogenesis with lipolysis to produce fatty acid networks that support malignancy. Monoacylglycerol lipase (MAGL) plays a principal role in this process by converting monoglycerides, including the endocannabinoid 2-arachidonoylglycerol (2-AG), to free fatty acids. Here, we show that MAGL is elevated in androgen-independent versus androgen-dependent human prostate cancer cell lines, and that pharmacological or RNA-interference disruption of this enzyme impairs prostate cancer aggressiveness. These effects were partially reversed by treatment with fatty acids or a cannabinoid receptor-1 (CB1) antagonist, and fully reversed by cotreatment with both agents. We further show that MAGL is part of a gene signature correlated with epithelial-to-mesenchymal transition and the stem-like properties of cancer cells, supporting a role for this enzyme in protumorigenic metabolism that, for prostate cancer, involves the dual control of endocannabinoid and fatty acid pathways.

Lycopene inhibits the proliferation of androgen-dependent human prostate tumor cells through activation of PPARγ-LXRα-ABCA1 pathway

The activation of nuclear receptors, peroxisome proliferator-activated receptor gamma (PPARγ) and liver X receptor alpha (LXRα), has been shown to inhibit the growth of prostate cancer cells. This study examined whether the anti-proliferative effect of lycopene on androgen-dependent human prostate cancer (LNCaP) cells involves the up-regulation of the expression of PPARγ and LXRα. As expected, lycopene treatment (2.5–10 μM) significantly inhibited the proliferation of LNCaP cells during incubation for 96 h. Lycopene significantly increased the protein and mRNA expression of PPARγ and LXRα at 24 and 48 h, while the increased in the expression of ATP-binding cassette transporter 1 (ABCA1) was only evident 96 h. In addition, lycopene significantly decreased cellular total cholesterol levels and increased apoA1 protein expression at 96 h. Incubation of LNCaP cells with lycopene (10 μM) in the presence (20 μM) of a specific antagonist of PPARγ (GW9662) and LXRα (GGPP) restored the proliferation of LNCaP cells to the control levels and significantly suppressed protein expression of PPARγ and LXRα as well as increased cellular total cholesterol levels. LXRα knockdown by siRNA against LXRα significantly enhanced the proliferation of LNCaP cells, whereas si-LXRα knockdown followed by incubation with lycopene (10 μM) restored the proliferation to the control level. The present study is the first to demonstrate that the anti-proliferative effect of lycopene on LNCaP cells involves the activation of the PPARγ-LXRα-ABCA1 pathway, leading to reduced cellular total cholesterol levels.

Abstract B50: Antiproliferative activity of the polar extract of Justicia spicigera on LNCaP cells

Abstract Justicia spicigera is a Mexican plant employed in traditional medicine for treatment of anemia, stomach illness and skin diseases. Furthermore, it has been suggested that this plant has anticancer properties on leukemia patients and in other types of cancer. However, the scientific evidence supporting these properties is not sufficient. The aim of this study was to evaluate the effect of Justicia spicigera on proliferation and viability of the androgen-dependent human prostate cancer cell line, LNCaP.A polar extract was obtained by exhaustive maceration with water and ethanol (v/v) of the air parts of the plant. The phytochemical analysis by the color test and thin layer chromatography (TLC) showed the presence of antioxidant compounds like coumarins, flavonoids and anthocyanins, which was corroborated by Nuclear Magnetic Resonance (H1 NMR). At the same time, the extract showed the presence of polyphenolic compounds detected by the Folin-Ciocalteu's reagent. The reducing power and the free radical scavenging capacity, was not too high in comparison with other less polar extracts of this plant, this could be explained by the high rate of glycosylation of the compounds in the sample. In the other hand, the polar extract of Justicia spicigera showed an antiproliferative activity on LNCaP cells since 500 g/ml of extract, measured by the MTT assay and direct cell account. Interestingly, cell morphology was not affected under these conditions. Likewise, the same extract did not show a relevant citotoxic effect (MTT assay) or an affectation on cellular viability (trypan blue assay) of LNCaP cells. Our study showed an antiproliferative effect of the polar extract of Justicia spicigera on LNCaP cells suggesting a potential use as anticancer agent. Further studies should focus on the characterization of compounds responsible of the effects observed on LNCaP cells, as well as in the definition of the mechanisms by which they affect the growth of these cells. Citation Information: Cancer Prev Res 2010;3(12 Suppl):B50.

Abstract 4386: Androgen Receptor Requires JunD as a Co-activator to Switch on an Oxidative Stress Generation Pathway in Prostate Cancer Cells

Abstract The relatively high oxidative stress in the prostate is postulated to be one of the major factors for prostate carcinogenesis and prostate cancer (CaP) progression. We focused on elucidating metabolic pathways of oxidative stress generation in CaP cells. Previously, we have shown that the transcription factor JunD is essential for the androgen-induced reactive oxygen species (ROS) production in androgen-dependent LNCaP human prostate cancer cells. We have also recently demonstrated that androgen induces the first and the regulatory enzyme spermidine/spermine N1-acetyl transferase (SSAT) in a polyamine catabolic pathway that produces copious amounts of metabolic ROS. Here, we present co-immunoprecipitation and Gaussia luciferase reconstitution assay data that show that JunD forms a complex with activated AR in situ. Our chromatin immnoprecipitation (ChIP) assay data demonstrate that JunD binds directly with a specific SSAT promoter sequence only in androgen-treated LNCaP cells. Using a vector containing a luciferase reporter gene connected to the SSAT promoter and a JunD silenced LNCaP cell line, we show that JunD is an essential co-activator of androgen-induction of SSAT gene expression. As there is no Androgen Response Element (ARE) in the SSAT promoter, we hypothesize that JunD mediates binding of androgen-activated AR to the SSAT promoter for the induction of SSAT that leads to polyamine oxidation and ROS production in prostate cells. Elucidation of this pathway may help the design of inhibitors of oxidative stress generation specifically in prostate cells to prevent prostate cancer occurrence and progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4386.

A neutralizing anti‐fibroblast growth factor (FGF) 8 monoclonal antibody shows anti‐tumor activity against FGF8b‐expressing LNCaP xenografts in androgen‐dependent and ‐independent conditions

Fibroblast growth factor 8-isoform b (FGF8b) has been detected in human clinical sex-organ related cancers including hormone-refractory prostate cancer. There are, however, few relevant experimental models. A murine monoclonal anti-FGF8 antibody, KM1334, has been shown to neutralize FGF8b and inhibit the growth of androgen-dependent mouse mammary SC-3 cells in vitro and in vivo. In the present study, we evaluated the anti-tumor activity of KM1334 against androgen-dependent and -independent progression of FGF8b-expressing human prostate cancer xenografts. FGF8b cDNA was transfected into androgen-dependent human prostate cancer cell line LNCaP, and its xenograft tumors were established subcutaneously in SCID mice with or without castration. KM1334 at the dose of 400 microg/head was injected twice weekly. FGF8b-expressing LNCaP cells secreted FGF8b, showed enhanced level of Erk1/2 phosphorylation, and showed more potent growth properties than mock-expressing cells in vitro and in vivo. KM1334 reduced these properties in vitro, inhibited tumorigenecity in vivo (T/C=0.33), and showed anti-tumor activity against established tumors (T/C=0.47) of FGF8b-expressing cells. FGF8b-expressing LNCaP tumors were androgen-dependent. However, they recurred as androgen-independent FGF8b positive tumors after castration. KM1334 also inhibited the growth of established FGF8b-expressing tumors in the androgen-independent states (T/C=0.47). These results indicate that humanized monoclonal antibodies, conserving the paratope of KM1334, are a promising candidate for therapy of FGF8b-expressing clinical prostate cancers. Follow-up studies using xenograft models with clinical FGF8b-expressing tumors are required to validate these early findings.

Piper cubeba Targets Multiple Aspects of the Androgen-Signalling Pathway. A Potential Phytotherapy against Prostate Cancer Growth?

Despite the high prevalence of prostate cancer (PC) in the Western world, there is a dearth of effective medication. Since the androgen-signalling pathway is very much involved in PC growth and development, we investigated the potential of Piper cubeba L. extract, P9605, in targeting multiple events simultaneously within this pathway. This may be more effective compared to an antiandrogen monotherapy. Our results indicated that P9605 inhibited proliferation in androgen-dependent LNCaP human prostate cancer cells by reducing DNA synthesis and inducing apoptosis. This antigrowth effect was less pronounced in androgen-independent PC-3 prostate cancer cell lines. P9605 potently inhibited 5 alpha-reductase II activity, which is responsible for converting testosterone to its active form, dihydrotestosterone (DHT), in the prostate. It also acted as an antagonist at recombinant wild-type androgen receptors (AR). P9605 suppressed cell growth and prostate-specific antigen (PSA) secretion stimulated by physiological concentrations of DHT in LNCaP cells. Interestingly, it down-regulated AR levels. In conclusion, our findings suggest that P9605 may potentially retard the growth of androgen-dependent PC via several mechanisms.