CWR22 Xenograft Research Articles

Reduced NCOR2 expression accelerates androgen deprivation therapy failure in prostate cancer.

SUMMARYThis study addresses the roles of nuclear receptor corepressor 2 (NCOR2) in prostate cancer (PC) progression in response to androgen deprivation therapy (ADT). Reduced NCOR2 expression significantly associates with shorter disease-free survival in patients with PC receiving adjuvant ADT. Utilizing the CWR22 xenograft model, we demonstrate that stably reduced NCOR2 expression accelerates disease recurrence following ADT, associates with gene expression patterns that include neuroendocrine features, and induces DNA hypermethylation. Stably reduced NCOR2 expression in isogenic LNCaP (androgen-sensitive) and LNCaP-C4–2 (androgen-independent) cells revealed that NCOR2 reduction phenocopies the impact of androgen treatment and induces global DNA hypermethylation patterns. NCOR2 genomic binding is greatest in LNCaP-C4–2 cells and most clearly associates with forkhead box (FOX) transcription factor FOXA1 binding. NCOR2 binding significantly associates with transcriptional regulation most when in active enhancer regions. These studies reveal robust roles for NCOR2 in regulating the PC transcriptome and epigenome and underscore recent mutational studies linking NCOR2 loss of function to PC disease progression.

The p14ARF tumor suppressor restrains androgen receptor activity and prevents apoptosis in prostate cancer cells.

Prostate cancer (PCa) is characterized by a unique dependence on optimal androgen receptor (AR) activity where physiological androgen concentrations induce proliferation but castrate and supraphysiological levels suppress growth. This feature has been exploited in bipolar androgen therapy (BAT) for castrate resistant malignancies. Here, we investigated the role of the tumor suppressor protein p14ARF in maintaining optimal AR activity and the function of the AR itself in regulating p14ARF levels. We used a tumor tissue array of differing stages and grades to define the relationships between these components and identified a strong positive correlation between p14ARF and AR expression. Mechanistic studies utilizing CWR22 xenograft and cell culture models revealed that a decrease in AR reduced p14ARF expression and deregulated E2F factors, which are linked to p14ARF and AR regulation. Chromatin immunoprecipitation studies identified AR binding sites upstream of p14ARF. p14ARF depletion enhanced AR-dependent PSA and TMPRSS2 transcription, hence p14ARF constrains AR activity. However, p14ARF depletion ultimately results in apoptosis. In PCa cells, AR co-ops p14ARF as part of a feedback mechanism to ensure optimal AR activity for maximal prostate cancer cell survival and proliferation.

O-9 - Network analysis of prostate cancer-derived CWR22, LNCaP and VCAP xenografts for elucidation of the key regulators in castration resistance development

O-9 - Network analysis of prostate cancer-derived CWR22, LNCaP and VCAP xenografts for elucidation of the key regulators in castration resistance development

Abstract B033: Characterizing the global function of NCOR2 in prostate cancer cells and its contribution to PCa progression

Abstract The nuclear receptor corepressors (NCORs) serve as critical mediators between transcription factors and epigenetic regulators, and thus their functions are critical in the maintenance of epigenetic and transcriptional states. As such, NCORs have important developmental and homeostatic roles, and disruptions of their functions are implicated in various cancers. In hormonally driven cancers, such as breast and prostate cancer (PCa), NCORs are implicated in de novo and acquired changes to steroid hormone signaling and therapeutic resistance. Supporting the importance of NCOR function in the prostate, inactivating genomic aberrations to NCORs have been identified in androgen deprivation therapy (ADT) resistant disease. However, to date, the global functions of NCORs in prostate cancer cells and their overall contributions to PCa progression remain enigmatic. To characterize the global functions of NCOR2/SMRT in prostate cancer we have undertaken efforts to map the NCOR2 dependent transcriptome (RNA-seq), miRnome (miRNA-seq), methylome (EPIC methylation array) and cistrome (ChIP-seq) in both androgen-sensitive (LNCaP) and ADT-resistant (LNCaP-C42) prostate cancer cells upon shRNA targeted knockdown. NCOR2 loss in LNCaP-C42 cells revealed a striking degree of global hypermethylation (87,078 CpGs > 10% gain, adj.pval < 0.01), while relatively little hypomethylation was observed (1,742 CpGs > 10% loss). Hypermethylation was largely exclusive of TSS loci and CpG islands, occurring at distal regions. Conversely, the NCOR2 associated transcriptome was more divergent in its expression changes by comparable criteria (1,491 upregulated, 1,195 downregulated). Similar patterns were observed in LNCaP cells, albeit to a lesser extent, suggesting broader regulatory roles in ADT resistant cells. NCOR2 knockdown deregulated a number of miRNA including let-7e and miR-200a with target binding motifs significantly enriched among the NCOR2 regulated transcriptome, and several of these miRNA stratified survival in PCa patient data. Furthermore, NCOR2 binding at candidate loci distinguished normal from malignant prostate cells, and global binding profiles revealed significant overlap with androgen receptor and pioneering factor FOXA1. To examine the effect of NCOR2 loss in the context of androgen signaling, similar experimental conditions were performed in the presence of dihydrotestosterone (DHT). NCOR2 control of androgen sensitivity was complex, resulting in amplified signaling of some classic AR target genes (KLK3, HERC3) while dampening others (TMPRSS2, TIPARP). Ongoing data integration efforts will dissect novel NCOR2 methylome-cistrome-transcriptome relationships within and across models to define target gene networks that are epigenetically governed through NCOR2 function. To determine whether NCOR2 loss alters PCa progression we have utilized stable introduction of NCOR2 targeting shRNA in the CWR22 xenograft model that simulates androgen-dependent primary growth, regression upon ADT, and subsequent recurrence at established proportions. NCOR2 loss had no effect on primary tumor growth rate or size of tumor at ADT. However, shNCOR2 expressing tumors had significantly reduced regression in response to ADT, and furthermore at 180 days post injection, a significantly higher proportion of shNCOR2 expressing tumors (17/49) had reached recurrence compared to shCTL tumors (7/46). In total, these findings place NCOR2 as an important epigenetic regulator in prostate cancer cells, the dysfunction of which contributes to PCa progression. Citation Format: Mark D. Long, Prashant K. Singh, Gerard Llimos, Spencer Rosario, Dominic J. Smiraglia, Moray J. Campbell. Characterizing the global function of NCOR2 in prostate cancer cells and its contribution to PCa progression [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B033.

Abstract 5865: Gartanin, a 4-prenylated xanthone in the mangosteen fruit, inhibits the growth of prostate cancer cells associated with Skp2 degradation via neddylation inhibition and FBXW2 induction

Abstract The S-phase kinase-associated protein 2 (Skp2) is overexpressed in prostate cancer and associated with tumor stage, disease recurrence, and worse patient survival. Studies also have demonstrated that Skp2 overexpression plays a critical role in development and progression of prostate cancer in several prostate cancer models, including PTEN knockout and TRAMP carcinogenesis and CWR22 xenograft models. Therefore, Skp2 is a promising target for developing new therapeutic and preventive approaches for prostate cancer. Here, we have found that gartanin, 4-prenylated xanthone from the Garcinia mangostana fruit (mangosteen), promoted Skp2 degradation in a proteasome-dependent manner in prostate cancer cells. In addition, gartanin induced the expression of FBXW2, a novel E3 ligase of SKP2 for targeted degradation, and downregulated the expression of NEDD8, leading to reduced neddylation levels of UBC12 and Cullin1. Molecular modelling analysis predicts that gartanin reasonably docks onto the regulatory subunit of NEDD8 activating enzyme E1 (NAE1) and next to the NEDD8 binding complex. More interestingly, gartanin selectively inhibits the growth of Skp2 overexpressing PC3 cells compared to parental PC cells (IC50 values for PC3/Skp2 vs. PC3 cells are approximately 4 μM vs. 14 μM). Together, our data indicate that gartanin is a novel natural agent for targeting Skp2 degradation via induction of FBXW2 expression and inhibition of neddylation. Gartanin deserves further investigation for its usefulness in prostate cancer prevention and treatment. Citation Format: Victor Pham, Michelle Bui, Raymond Rendon, Ericka Agredano, Thanh Le, Liankun Song, Xiaolin Zi. Gartanin, a 4-prenylated xanthone in the mangosteen fruit, inhibits the growth of prostate cancer cells associated with Skp2 degradation via neddylation inhibition and FBXW2 induction [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5865.

Effect of HER3 dimer feedback upregulation via PI3K-AKT-mTOR pathway inhibition on androgen receptor (AR) stabilization in metastatic prostate cancer.

226 Background: Metastatic castration resistant prostate cancer (CRPC) is dependent on persistent activation of the AR. In addition, the AR and PI3K-AKT-mTOR pathways have been shown to regulate each other through complex feedback mechanisms. Various early phase clinical studies are currently investigating the role of PI3K-AKT-mTOR pathway inhibitors in improving outcomes in metastatic CRPC. We hypothesise that the formation of a HER3 (human epidermal growth factor receptor) heterodimer, has an important role in regulating the AR and PI3K-AKT-mTOR feedback loop and that its detection can predict response to PI3K-AKT-mTOR pathway inhibition. Methods: LNCAP cells were stably lentiviral transduced with shRNA against HER3. The effect of PI3K-AKT-mTOR inhibition by DS7423, GDC0068, GDC0941 and Everolimus on AR and its direct target gene PSA was evaluated by western blot and real-time quantitative PCR. CWR22 and 22RVI mouse xenograft tumours were stained with fluorescently labelled antibodies for fluorescence lifetime imaging microscopy (FLIM) to assess HER2-HER3 dimerisation by FRET (fluorescence resonance energy transfer) using TRI2 software. Results: We show that there is a statistically significant increase in AR protein levels and PSA gene expression in LNCAP NTC vs HER3kd cells upon treatment with the dual PI3K-mTOR inhibitor DS7423. In addition, there is decreased inhibition of AKT phosphorylation in LNCAP NTC cells, whereas in the absence of HER3 there is complete abrogation of pAKT levels. The use of GDC0941 and Everolimus resulted in similar effect on AR in the LNCAP NTC vs HER3kd cells, however this is less prominent. The AKT inhibitor, GDC0068, has little effect on AR in the presence or absence of HER3. FLIM demonstrated increase in FRET as evidence of HER3 heterodimerisation in 22RVI compared to CWR22 xenograft tissue, showing that HER3 dimerisation emerges in metastatic prostate cancer that has progressed to a castrate resistant phenotype. Conclusions: Our results suggest that HER3 stabilises the AR upon PI3K-AKT- mTOR pathway inhibition and that detection of a HER3 heterodimer can be used as a predictive biomarker of response to these therapies.

MP87-12 ADRENAL ANDROGENS FACILITATE PROSTATE CANCER CELL RESISTANCE TO ANDROGEN DEPRIVATION THERAPY

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology III1 Apr 2017MP87-12 ADRENAL ANDROGENS FACILITATE PROSTATE CANCER CELL RESISTANCE TO ANDROGEN DEPRIVATION THERAPY Michael Fiandalo, John Stocking, Elena Pop, Krystin Mantione, John Wilton, and James Mohler Michael FiandaloMichael Fiandalo More articles by this author , John StockingJohn Stocking More articles by this author , Elena PopElena Pop More articles by this author , Krystin MantioneKrystin Mantione More articles by this author , John WiltonJohn Wilton More articles by this author , and James MohlerJames Mohler More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.2716AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Prostate Cancer (CaP) growth and survival is dependent on the interaction of androgen receptor (AR) and testicular androgens, testosterone and dihydrotestosterone (DHT). Men that fail potential curative treatment are treated with androgen deprivation therapy (ADT). ADT is palliative and CaP recurs as the lethal phenotype. One mechanism that contributes to CaP recurrence is intratumoral intracrine androgen metabolism, which is the conversion of weak adrenal androgens (androstenedione [ASD] or dehydroepiandrosterone [DHEA]) to T or DHT. Mice lack adrenal androgens and therefore adrenal androgen contribute to CaP xenograft recurrence is overlooked. The hypothesis for these studies is adrenal androgen supplementation will facilitate androgen dependent human CaP CWR22 xenograft resistance to ADT. METHODS Mice were castrated, implanted with CWR22 and silastic tubes that contained T and empty silastic tubes that contained ASD or DHEA. T silastic tubes were removed after CWR22 tumor volumes reached 0.5 cc to simulate ADT. Digital calipers were used to measure changes in CWR22 tumor volume. Mouse serum, prostate and CWR22 were harvested at designated time points and liquid chromatography tandem-mass spectrometry (LC-MS/MS) was performed to measure androgen levels. RESULTS CWR22 xenografts treated with no adrenal androgen regressed and began to grow 120 days after T silastic tube removal. ASD treated CWR22 tumors did not regress; CWR22 tumor growth increased and mice were euthanized because tumors grew beyond veterinary limits. DHEA treated CWR22 did not regress and did not grow like ASD treated CWR22. However, CWR22 xenografts recurred faster than control CWR22 xenografts. Serum PSA levels correlated with tumor volume. CWR22 androgen levels decreased in all treatment groups, but T levels remained sufficient to activate AR in ASD treated CWR22, but not control or DHEA treated CWR22 xenografts. CONCLUSIONS DHEA and ASD supplementation facilitated CWR22 resistance to ADT. However, CWR22 xenografts responded differently to DHEA and ASD, which suggests that adrenal androgens may play different roles when CaP cells undergo ADT. These studies show that adrenal androgen contributes should be taken into account when in vivo studies are performed to test CaP responses to ADT or therapeutic agents. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e1170 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Michael Fiandalo More articles by this author John Stocking More articles by this author Elena Pop More articles by this author Krystin Mantione More articles by this author John Wilton More articles by this author James Mohler More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Up-Regulation of Follistatin-Like 1 By the Androgen Receptor and Melanoma Antigen-A11 in Prostate Cancer.

High affinity androgen binding to the androgen receptor (AR) activates genes required for male sex differentiation and promotes the development and progression of prostate cancer. Human AR transcriptional activity involves interactions with coregulatory proteins that include primate-specific melanoma antigen-A11 (MAGE-A11), a coactivator that increases AR transcriptional activity during prostate cancer progression to castration-resistant/recurrent prostate cancer (CRPC). Microarray analysis and quantitative RT-PCR were performed to identify androgen-regulated MAGE-A11-dependent genes in LAPC-4 prostate cancer cells after lentivirus shRNA knockdown of MAGE-A11. Chromatin immunoprecipitation was used to assess androgen-dependent AR recruitment, and immunocytochemistry to localize an androgen-dependent protein in prostate cancer cells and tissue and in the CWR22 human prostate cancer xenograft. Microarray analysis of androgen-treated LAPC-4 prostate cancer cells indicated follistatin-like 1 (FSTL1) is up-regulated by MAGE-A11. Androgen-dependent up-regulation of FSTL1 was inhibited in LAPC-4 cells by lentivirus shRNA knockdown of AR or MAGE-A11. Chromatin immunoprecipitation demonstrated AR recruitment to intron 10 of the FSTL1 gene that contains a classical consensus androgen response element. Increased levels of FSTL1 protein in LAPC-4 cells correlated with higher levels of MAGE-A11 relative to other prostate cancer cells. FSTL1 mRNA levels increased in CRPC and castration-recurrent CWR22 xenografts in association with predominantly nuclear FSTL1. Increased nuclear localization of FSTL1 in prostate cancer was suggested by predominantly cytoplasmic FSTL1 in benign prostate epithelial cells and predominantly nuclear FSTL1 in epithelial cells in CRPC tissue and the castration-recurrent CWR22 xenograft. AR expression studies showed nuclear colocalization of AR and endogenous FSTL1 in response to androgen. AR and MAGE-A11 cooperate in the up-regulation of FSTL1 to promote growth and progression of CRPC. Prostate 77:505-516, 2017. © 2016 Wiley Periodicals, Inc.

Hypoxia regulates Notch-3 mRNA and receptor activation in prostate cancer cells

The Notch-3 receptor is a recognized key regulator of vascular responses and is increasingly associated with tumorigenesis. Hypoxia-inducible factors activate specific signaling pathways such as Notch in a number of cellular models. This study aimed to evaluate the regulation of Notch-3 by hypoxia in prostate cancer cells. Notch-3 gene and protein expression was established in a panel of aerobic and hypoxic prostate cell lines in vitro, the CWR22 xenograft model and RNA extracted from low grade (Gleason score < = 6); high grade (Gleason score > = 7); non-hypoxic (low HIF, low VEGF); hypoxic (high HIF, high VEGF) patient FFPE specimens. NOTCH-3 was upregulated in PC3 (3-fold), 22Rv1 (4.1-fold) and DU145 (3.8-fold) but downregulated in LnCaP (12-fold) compared to the normal cell lines. NOTCH-3 expression was modified following hypoxic exposure in these cells. NOTCH-3 was upregulated (2.2-fold) in higher grade and hypoxic tumors, when compared to benign and aerobic pools. In the CWR22 xenograft model, Notch-3 expression was restored in castrate resistant tumors. Nuclear translocation of the Notch-3 intracellular domain was no longer detected following exposure of cells to hypoxia but not associated with a change in expression of HES-1. Our data further identifies Notch-3 as a potentially key hypoxic-responsive member of the Notch pathway in prostate tumorigenesis.

Abstract 5051: Androgen receptor-mediated regulation of p14ARF transcription in prostate tumor cells

Abstract The p14ARF tumor suppressor is often deleted or silenced in malignancies. Prostate tumors are an exception, where p14 expression is elevated. To understand this phenomenon, we assessed the expression of p53 pathway members, which are most effected by p14ARF. The expression of androgen receptor (AR), a pivotal prostate cancer regulator, which is also affected by p14arf and MDM2 was analyzed as well. The studies used archival prostate tumor tissues obtained from prostatectomies performed at the Veterans Affairs-Northern California Health Care System in Mather California between 1996 and 2002 to better define the relationship between these interrelated networks. A prostate tumor tissue array consisting of 78 tumors of differing stages and grades was constructed to evaluate correlations between multiple parameters. Immunohistochemical studies assessed expression of the proliferation marker Ki67, p53, MDM2, MDM4, p14ARF, and the AR in the nuclear and cytoplasmic compartments of tumor and adjacent cells. p53, MDM4, p14ARF and AR were detected in nuclear and cytoplasmic compartments of tumor and non-tumor cells, but were predominantly nuclear. MDM2 expression was primarily cytoplasmic in tumor cells. Multivariate analysis of the immunohistochemical markers identified a strong correlation between expression of p14ARF and AR. Studies utilizing the prostate CWR22 xenograft and LNCaP cell line models revealed that castration or androgen deprivation resulted in reduced p14arf levels and that this effect correlated with a precipitous decline in E2F1-3a levels. In a reciprocal analysis, RB ablation enhanced p14ARF transcription, arguing that the E2F/RB pathway mediates AR-dependent p14ARF expression. However, we also identified an AR binding site located ∼40 KB upstream of the p14ARF gene. Chromatin immunoprecipitation (ChIP) studies showed that in prostate cells this site was bound by AR. ChIP studies also revealed E2F1 and E2F3 were present at the p14ARF promoter. Together, the studies argue p14ARF is a direct transcriptional target of AR and that AR and E2F collaborate to promote p14ARF expression. . Citation Format: Maria Mudryj, Salma Siddiqui, Stephen J. Libertini, Alan P. Lombard, Benjamin Mooso, Leandro D'Abronzo, Frank Melgoza, Alexander Borowsky, Christiana Drake, LiHong Qi, Paramita M. Ghosh. Androgen receptor-mediated regulation of p14ARF transcription in prostate tumor cells. [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 5051. doi:10.1158/1538-7445.AM2015-5051

The novel toluidine sulphonamide EL102 shows pre-clinical in vitro and in vivo activity against prostate cancer and circumvents MDR1 resistance

Background:Taxanes are routinely used for the treatment of prostate cancer, however the majority of patients eventually develop resistance. We investigated the potential efficacy of EL102, a novel toluidine sulphonamide, in pre-clinical models of prostate cancer.Methods:The effect of EL102 and/or docetaxel on PC-3, DU145, 22Rv1 and CWR22 prostate cancer cells was assessed using cell viability, cell cycle analysis and PARP cleavage assays. Tubulin polymerisation and immunofluorescence assays were used to assess tubulin dynamics. CWR22 xenograft murine model was used to assess effects on tumour proliferation. Multidrug-resistant lung cancer DLKPA was used to assess EL102 in a MDR1-mediated drug resistance background.Results:EL102 has in vitro activity against prostate cancer, characterised by accumulation in G2/M, induction of apoptosis, inhibition of Hif1α, and inhibition of tubulin polymerisation and decreased microtubule stability. In vivo, a combination of EL102 and docetaxel exhibits superior tumour inhibition. The DLKP cell line and multidrug-resistant DLKPA variant (which exhibits 205 to 691-fold greater resistance to docetaxel, paclitaxel, vincristine and doxorubicin) are equally sensitive to EL102.Conclusion:EL102 shows potential as both a single agent and within combination regimens for the treatment of prostate cancer, particularly in the chemoresistance setting.

Hypoxia-Independent Downregulation of Hypoxia-Inducible Factor 1 Targets by Androgen Deprivation Therapy in Prostate Cancer

We explored changes in hypoxia-inducible factor 1 (HIF1) signaling during androgen deprivation therapy (ADT) of androgen-sensitive prostate cancer xenografts under conditions in which no significant change in immunostaining of the hypoxia marker pimonidazole had occurred. Gene expression profiles of volume-matched androgen-exposed and androgen-deprived CWR22 xenografts, with similar pimonidazole-positive fractions, were compared. Direct targets of androgen receptor (AR) and HIF1 transcription factors were identified among the differentially expressed genes by using published lists. Biological processes affected by ADT were determined by gene ontology analysis. HIF1α protein expression in xenografts and biopsy samples from 35 patients receiving neoadjuvant ADT was assessed by immunohistochemistry. A total of 1344 genes showed more than 2-fold change in expression by ADT, including 35 downregulated and 5 upregulated HIF1 targets. Six genes were shared HIF1 and AR targets, and their downregulation was confirmed with quantitative RT-PCR. Significant suppression of the biological processes proliferation, metabolism, and stress response in androgen-deprived xenografts was found, consistent with tumor regression. Nineteen downregulated HIF1 targets were involved in those significant biological processes, most of them in metabolism. Four of these were shared AR and HIF1 targets, including genes encoding the regulatory glycolytic proteins HK2, PFKFB3, and SLC2A1. Most of the downregulated HIF1 targets were induced by hypoxia in androgen-responsive prostate cancer cell lines, confirming their role as hypoxia-responsive HIF1 targets in prostate cancer. Downregulation of HIF1 targets was consistent with the absence of HIF1α protein in xenografts and downregulation in patients by ADT (P<.001). AR repression by ADT may lead to downregulation of HIF1 signaling independently of hypoxic fraction, and this may contribute to tumor regression. HIF1α expression is probably not a useful hypoxia biomarker during ADT in prostate cancer.

Androgen Signaling Promotes Translation of TMEFF2 in Prostate Cancer Cells via Phosphorylation of the α Subunit of the Translation Initiation Factor 2

The type I transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2), is expressed mainly in brain and prostate. Expression of TMEFF2 is deregulated in prostate cancer, suggesting a role in this disease, but the molecular mechanism(s) involved in this effect are not clear. Although androgens promote tmeff2 transcription, androgen delivery to castrated animals carrying CWR22 xenografts increases TMEFF2 protein levels in the absence of mRNA changes, suggesting that TMEFF2 may also be post-transcriptionally regulated. Here we show that translation of TMEFF2 is regulated by androgens. Addition of physiological concentrations of dihydrotestosterone (DHT) to prostate cancer cell lines increases translation of endogenous TMEFF2 or transfected TMEFF2-Luciferase fusions, and this effect requires the presence of upstream open reading frames (uORFs) in the 5′-untranslated region (5′-UTR) of TMEFF2. Using chemical and siRNA inhibition of the androgen receptor (AR), we show that the androgen effect on TMEFF2 translation is mediated by the AR. Importantly, DHT also promotes phosphorylation of the α subunit of the translation initiation factor 2 (eIF2α) in an AR-dependent manner, paralleling the effect on TMEFF2 translation. Moreover, endoplasmic reticulum (ER) stress conditions, which promote eIF2α phosphorylation, also stimulate TMEFF2 translation. These results indicate that androgen signaling promotes eIF2α phosphorylation and subsequent translation of TMEFF2 via a mechanism that requires uORFs in the 5′-UTR of TMEFF2.

18 F]-2′ -Fluoro-5-methyl-1-beta-D-arabinofuranosyluracil ( 18 F-FMAU) in Prostate Cancer: Initial Preclinical Observations

We hypothesized that imaging-based assessment of cellular proliferation in prostate cancer may improve tumor characterization. We therefore evaluated the biodistribution and effect of androgen on tumor uptake of the cellular proliferation imaging marker [(18)F]-2'-fluoro-5-methyl-1-beta-D-arabinofuranosyluracil ((18)F-FMAU) in xenograft mouse models of human prostate cancer. Castrated and noncastrated athymic male mice were implanted with androgen-independent PC3 and androgen-sensitive CWR22 human prostate cancer cells. Dynamic micro-positron emission tomography (PET)/computed tomography was performed for 1 hour followed by 10-minute static scans at 2 and 3 hours. Animals were sacrificed after imaging for biodistribution studies and immunohistochemical staining of tumors for androgen receptor and Ki-67/MIB expression. (18)F-FMAU uptake was significantly higher in all major organs of the castrated animals in comparison with noncastrated mice, with the highest uptake in liver and the lowest uptake in muscle and bone. When compared to PC3 tumors, CWR22 xenografts showed significantly higher tumor to muscle (2.56 ± 0.30 vs 1.99 ± 0.30, p = .008) and tumor to liver (1.72 ± 0.12 vs 1.26 ± 0.17, p = .0003) uptake ratios in the noncastrated animal at the 3-hour time point. Androgen receptor and Ki-67/MIB expressions were higher in CWR22 than in PC3 xenografts. Our initial preclinical observations suggest that there may be an association between androgen signaling and thymidine metabolism and that (18)F-FMAU PET may be useful in prostate tumor characterization.

Altered corepressor SMRT expression and recruitment to target genes as a mechanism that change the response to androgens in prostate cancer progression

Androgen receptor (AR) is required for the development and progression of prostate cancer (CaP) from androgen-dependence to androgen-resistance. Both corepressors and coactivators regulate AR-mediated transcriptional activity, and aberrant expression or activity due to mutation(s) contributes to changes in AR function in the progression to androgen resistance acquired during hormonal ablation therapies. Primary culture of epithelial cells from androgen-dependent CWR22 and androgen-resistant CWR22R xenograft tumors were used to evaluate the effect of androgens on AR function, and the association with coactivators (SRC-1 and TIF-2) and corepressors (SMRT and NCoR). Both androgen-dependent CWR22 and androgen-resistant CWR22R cells expressed functional AR as the receptor bind ligand with high affinity and increased trafficking to the nuclei in the presence of androgens. However, in the presence of androgens, AR-mediated transcriptional activity in androgen-sensitive CWR22 cells was limited to a 2-fold increase, as compared to a 6-fold increase in androgen-resistance CWR22R cells. In androgen-sensitive CWR22 cells, immunoblot, confocal microscopy, and chromatin immunoprecipitation assays indicated that the androgen bound AR transcriptional initiation complex in the PSA promoter contained corepressor SMRT, resulting in limited receptor transcriptional activity. In contrast, increased AR-mediated transcriptional activity in the CWR22R cells was consistent with decreased expression and recruitment of the corepressors SMRT/NCoR, as well as increased recruitment of the coactivator TIF-2 to the receptor complex. Similar changes in the response to androgens were observed in the LNCaP/C4–2 model of androgen resistance prostate cancer. Thus, altered recruitment and loss of corepressors SMRT/NCoR may provide a mechanism that changes the response of AR function to ligands and contributes to the progression of the advanced stages of human prostate cancer.

Prostate cancer inhibitory activity of a novel dual inhibitor, EL102, in combination with docetaxel, and its effects on MDR1-mediated drug resistance in vitro.

e15126 Background: EL102 is a dual-action drug promoting apoptosis and inhibiting angiogenesis. It exerts its action though the inhibition of Hif1a induced hypoxic signalling and induction of the Caspase 3/7 apoptotic cascade. The drug has equal activity in normoxia and hypoxia indicating it may be equally active in these different tumor compartments. We tested its ability to circumvent chemotherapeutic drug resistance. Methods: We assessed the ability of EL102 to inhibit prostate cancer cell proliferation and motility in vitro, calculating IC50s for CWR22, 22Rv2, PC3 and DU145 prostate cancer cell lines, comparing sensitivity between androgen dependent, androgen independent and metastatic prostate cancer. Additionally we assessed the activity of EL102 in combination with docetaxel in vitro and in murine CWR22 xenografts. The ability to overcome MDR1 and BCRP mediated drug resistance was also tested using DLKP drug resistant variants which exhibit 200 fold resistance to doxorubicin, docetaxel, paclitaxel and vincristine. Results: We found that prostate cancer cell lines are sensitive to EL102 with IC50s in the region of 10-50nM. Of particular interest was the identical sensitivity of the androgen independent 22Rv1 and its androgen dependent parent CWR22, suggesting ability to overcome hormone refractory prostate cancer. Additionally we demonstrate dose response for inhibition of cell motility in metastatic DU145. In CWR22 murine mouse models treatment with EL102 resulted in decreased tumor volume compared to control. A docetaxel and EL102 combination arm demonstrated the greater inhibition of tumor growth than EL102 or docetaxel alone. The lung cancer cell line DLKP, its drug resistant variants DLKPA (MDR1 overexpressing) and DLKPMitox (BCRP overexpressing) were equally sensitive to EL102 indicating that EL102 is not a substrate for MDR1 or BCRP. Conclusions: EL102 is a potential therapeutic for the treatment of prostate cancer, in particular in combination with docetaxel, and exhbibits the potential to overcome drug resistane. Future studies will include the efficacy of this drug in prostate cancer metastatic mouse models.

Absence of XMRV and closely related viruses in primary prostate cancer tissues used to derive the XMRV-infected cell line 22Rv1.

The 22Rv1 cell line is widely used for prostate cancer research and other studies throughout the world. These cells were established from a human prostate tumor, CWR22, that was serially passaged in nude mice and selected for androgen independence. The 22Rv1 cells are known to produce high titers of xenotropic murine leukemia virus-related virus (XMRV). Recent studies suggested that XMRV was inadvertently created in the 1990's when two murine leukemia virus (MLV) genomes (pre-XMRV1 and pre-XMRV-2) recombined during passaging of the CWR22 tumor in mice. The conclusion that XMRV originated from mice and not the patient was based partly on the failure to detect XMRV in early CWR22 xenografts. While that deduction is certainly justified, we examined the possibility that a closely related virus could have been present in primary tumor tissue. Here we report that we have located the original prostate tumor tissue excised from patient CWR22 and have assayed the corresponding DNA by PCR and the tissue sections by fluorescence in situ hybridization for the presence of XMRV or a similar virus. The primary tumor tissues lacked mouse DNA as determined by PCR for intracisternal A type particle DNA, thus avoiding one of the limitations of studying xenografts. We show that neither XMRV nor a closely related virus was present in primary prostate tissue of patient CWR22. Our findings confirm and reinforce the conclusion that XMRV is a recombinant laboratory-generated mouse virus that is highly adapted for human prostate cancer cells.

Abstract 1800: Targeted therapy using saracatinib adjunctive to castration inhibits progression to castration-resistant prostate cancer in a murine model

Abstract Introduction: Prostate cancer treatment with androgen deprivation is typically efficacious for two years prior to the development of castration resistant disease (CRPC). The Src family kinases (SFK) are upregulated with androgen deprivation and have been implicated in the progression to CRPC. Saracatinib is a specific SFK inhibitor that inhibits castration resistant growth and metastases in an animal model using LNCaP cells overexpressing the neuropeptide gastrin-releasing peptide. We test the hypothesis that saracatinib given immediately after androgen deprivation inhibits castration resistant tumor recurrence using a CWR22 xenograft model. Materials and Methods: CWR22 prostate cancer xenografts were injected subcutaneously into nude mice primed with testosterone pellets (21-day release). Twenty-six mice were castrated after adequate tumor development (day 0). Mice in the treatment arm were administered saracatinib from day 7 to day 150. Mice were sacrificed at days 0, 3, 30 and 150. Tumors and sera were collected for analysis including tumor weight, serum testosterone, serum PSA and gene-profile studies. The data was analyzed using the t-test and analysis of variance. Results: CRPC recurrence was significantly inhibited with the administration of saracatinib. The mean weight of tumor recurrence was 0.18 grams with saracatinib compared to 3.20 grams in the control group (p=0.015). Saracatinib was associated with a reduction in serum PSA (1.6 versus 14.7 ng/dl) and testosterone (21.1 versus 24.1 pg/ml) compared to controls, though statistical significance was not reached (p=0.08 and p=0.63, respectively). Gene expression of signaling kinases and their downstream olecules including Src, Etk, FAK, JAK, Stat3, c-myc, β-catenin, NF-κB, Akt, and mTOR is being compared between time points. Conclusions: Saracatinib significantly inhibits castration resistant tumor recurrence when started with androgen deprivation. Additional investigation into the genetic and molecular changes induced by saracatinib with gene microarray and polymerase chain reaction is ongoing. Saracatinib may have a role in combination with androgen deprivation to delay the onset of castration resistant disease. 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 1800. doi:1538-7445.AM2012-1800

In vitro and in vivo evaluation of resveratrol and 3,5-dihydroxy-4'-acetoxy-trans-stilbene in the treatment of human prostate carcinoma and melanoma

BackgroundResveratrol (RESV) is a naturally occurring compound that may possess anticancer capabilities in both prostate carcinoma and melanoma. MethodsThe in vitro and in vivo cytotoxic activity of RESV and 3,5-dihydroxy-4'-acetoxy-trans-stilbene (4-ACE) was tested using cellular assays and a xenograft model. Five prostate carcinoma cell lines were used for in vitro evaluation. A melanoma cell line (Duke melanoma 738 [DM738]) and the prostate carcinoma line CWR22 were used for in vivo experiments. Mice were randomized to osmotic mini pumps with 200 μL of RESV (250 mg/mL), 4-ACE (335 mg/mL), or vehicle (50% dimethyl sulfoxide, 50% polyethylene glycol). Serum drug and metabolite levels were calculated by high-performance liquid chromatography with diode-array detection. Western blots were performed on treated tumors. Results were analyzed using a student’s t-test, analysis of variance, and the Mann–Whitney rank sum test. ResultsRESV and 4-ACE were cytotoxic in a time- and dose-dependent manner in all prostate carcinoma cell lines tested. Enhanced growth compared with controls was seen at the 24 h time point in four lines treated with RESV and two lines treated with 4-ACE (Ps < 0.048). In vivo, no difference in either tumor growth or postmortem tumor weight was detected in either DM738 (P = 0.555, P = 0.562) or CWR22 (P = 0.166, P = 0.811) xenografts treated with either drug. Serum drug levels did not correlate with tumor growth rates for any treatment group (all Ps > 0.11). Treated tumors demonstrated protein changes by western blot. ConclusionAlthough in vitro data were promising, RESV and 4-ACE have limited potential as single agents in the treatment of prostate carcinoma and melanoma.

From XMRV to HIV-1 and back

Xenotropic MLV-related retrovirus (XMRV) was first reported about 5 years ago in a few cases of prostate cancer, but did not attract much attention until its reported association with a large fraction of chronic fatigue syndrome cases about 2 years ago. The publication of the XMRV-CFS connection created a ripple of excitement and interest in the scientific, medical, and patient communities reminiscent of the reports of the association of another retrovirus—HIV-with AIDS some 25 years previously. Although I was not directly involved in either discovery at the time, I was a very interested observer who had been working with various retroviruses and who subsequently became involved in both HIV and research, and I will offer some observations on the parallels and differences between the two. It is noteworthy, that, within 2 years of the first report, in 1983, of the virus we now call HIV, the key findings were widely replicated by virologists using a variety of different assays. By contrast, most of the results of the paper - isolation of infectious virus from patients, frequent detection of virus in plasma and PBMCs by PCR, detection of antiviral antibodies - remain to be replicated outside of the laboratories that authored the original report despite considerable effort worldwide. HIV is now known as the cause of a global pandemic responsible for large numbers of deaths annually and considerable hardship and economic loss. By contrast, is considered by most virologists to be the consequence of a collection of artifacts originating from endogenous murine leukemia viruses prevalent in laboratory and wild mice. In this talk, I will discuss our recent work that uncovered how these associations arose and how even experienced retrovirologists were misled by the initial reports. There are several related, but distinct, issues that need to be considered. First, various mouse (Mus musculus) subspecies carry over a hundred different endogenous proviruses closely (>90%) related to in their DNA. Second, mice are extremely widespread, as is their DNA, which can be found sporadically on laboratory surfaces, as well as contaminants of common reagents and materials. Sensitive PCR assays can detect XMRV related sequences in DNA from tiny fractions of one cell. To detect such contamination, we developed a more sensitive assay based on mouse IAP sequences present in thousands of copies per cell. Third, although only a few of the endogenous MLV proviruses encode infectious virus, it has been known since the 1970s that some of them can give rise to virus that can infect human tumor lines when passaged through nude mice. Indeed, A virus identical to is produced by the 22RV1 prostate cancer line that was derived in just this way In initial reports, however, did not appear to be sufficiently similar to known proviruses to have been derived this way. However, we have recently shown that this is exactly how it did arise, but not from infection of the precursor CWR22 xenograft with a single virus, but rather with a recombinant between the progeny of two previously undescribed proviruses found in the nude mice used for passage. Since the predicted recombinant is ancestral to all isolates, and cannot have arisen more than once, it must have found its way into many laboratories as the 22Rv1 cell line was distributed worldwide and, by means that remain to be worked out, into clinical samples from CFS patients.