Activity In Prostate Cancer Cells Research Articles

The role of enzalutamide-induced hyperactive Jak2-Stat5 feed-forward signaling loop on enzalutamide-resistant prostate cancer growth and as a therapeutic target for second-line treatment.

221 Background: Androgen targeted therapy remains the mainstay for advanced prostate cancer (PC). Second-generation androgen receptor (AR) antagonist, enzalutamide (ENZ), re-targets persistent AR activity in castrate-resistant (CR) PC tumors, and is approved for CRPC. Despite initial clinical activity, acquired resistance to ENZ arises rapidly and most patients succumb to PC. Mechanisms underlying resistance to ENZ are incompletely understood. Prior work has established Stat5 as a potent inducer of PC growth. Here, we investigated the significance of Jak2-Stat5 signaling in ENZ-resistant growth of PC. Methods: Levels of Jak2 and Stat5 activation in PC cells, tumors and patient samples were evaluated by immunohistochemistry, 3D tumor explant cultures and western blotting. Jak2 and Stat5 were inhibited by lentiviral (expression of) shRNA or pharmacologically. Levels of mRNA were assessed by QPCR and gene expression profiling. Results: ENZ induced a robust increase in Stat5 activation in PC cells in vitro, in xenograft tumors in vivo and in patient-derived PCs during ENZ treatment. Mechanistically, ENZ activation of Stat5 involves a positive feed-forward mechanism where ENZ-liganded AR induces rapid and sustained Jak2 phosphorylation in PC cells through a process involving Jak2-specific phosphatases. This results in a formation of a positive feed-forward loop in PC where activated Stat5 induces Jak2 mRNA and protein levels in PC. We showed that active Stat5 increased viability of PC cells during ENZ treatment and, at the same time, inhibition of Stat5 as a second-line treatment induced excessive death of PC cells surviving ENZ treatment. Importantly, pharmacological Stat5 blockade inhibited CR growth of PC xenograft tumors after ENZ resistance developed. Conclusions: Collectively, this work introduces a novel concept for a pivotal role of Jak2-Stat5 signaling in mediating resistance of PC to ENZ. Pharmacological Jak2-Stat5 inhibition may provide efficacious therapy in advanced PC in combination with ENZ or after ENZ fails.

Proton pump inhibitors promote the growth of androgen-sensitive prostate cancer cells through ErbB2, ERK1/2, PI3K/Akt, GSK-3β signaling and inhibition of cellular prostatic acid phosphatase

Prostate cancer (PCa) is one of the most common cancer in men. Although hormone-sensitive PCa responds to androgen-deprivation, there are no effective therapies for castration-resistant PCa. It has been recently suggested that proton pump inhibitors (PPIs) may increase the risk of certain cancers; however, association with PCa remains elusive. Here, we evaluated the tumorigenic activities of PPIs in vitro, in PCa cell lines and epithelial cells from benign prostatic hyperplasia (BPH) and in vivo, in PCa mice xenografts. PPIs increased survival and proliferation, and inhibited apoptosis in LNCaP cells. These effects were attenuated or absent in androgen-insensitive DU-145 and PC3 cells, respectively. Specifically, omeprazole (OME) promoted cell cycle progression, increased c-Myc expression, ErbB2 activity and PSA secretion. Furthermore, OME induced the phosphorylation of MAPK-ERK1/2, PI3K/Akt and GSK-3β, and blunted the expression and activity of cellular prostatic acid phosphatase. OME also increased survival, proliferation and PSA levels in BPH cells. In vivo, OME promoted tumor growth in mice bearing LNCaP xenografts. Our results indicate that PPIs display tumorigenic activities in PCa cells, suggesting that their long-term administration in patients should be carefully monitored.

Vitamin D and testosterone co-ordinately modulate intracellular zinc levels and energy metabolism in prostate cancer cells

Vitamin D3 and its receptor are responsible for controlling energy expenditure in adipocytes and have direct roles in the transcriptional regulation of energy metabolic pathways. This phenomenon also has a significant impact on the etiology of prostate cancer (PCa). Using several in vitro models, the roles of vitamin D3 on energy metabolism and its implication in primary, early, and late invasive PCa were investigated. BODIPY staining and qPCR analyses show that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) up-regulates de novo lipogenesis in PCa cells by orchestrating transcriptional regulation that affects cholesterol and lipid metabolic pathways. This lipogenic effect is highly dependent on the interaction of several nuclear receptors and their corresponding ligands, including androgen receptor (AR), vitamin D receptor (VDR), and retinoid X receptor (RXR). In contrast, inhibition of peroxisome proliferator-activated receptor alpha (PPARα) signaling blocks the induction of the lipogenic phenotype induced by these receptors. Furthermore, 1,25(OH)2D3, T, and 9 cis-retinoic acid (9-cis RA) together redirect cytosolic citrate metabolism toward fatty acid synthesis by restoring normal prostatic zinc homeostasis that functions to truncate TCA cycle metabolism. 1,25(OH)2D3, T, and 9-cis RA also exert additional control of TCA cycle metabolism by down-regulating SLC25A19, which limits the availability of the co-factor thiamine pyrophosphate (TPP) that is required for enzymatic catalyzation of citrate oxidation. This extensive metabolic reprogramming mediated by 1,25(OH)2D3, T, and 9-cis RA is preserved in all in vitro cell lines investigated. These data suggest that 1,25(OH)2D3 and T are important regulators of normal prostatic energy metabolism. Based on the close association between energy metabolism and cancer progression, supplementation of vitamin D3 and testosterone can restrict the energy production that is required to drive PCa progression by maintaining proper zinc homeostasis and inhibiting TCA cycle activity in PCa cells.

ASPM promotes prostate cancer stemness and progression by augmenting Wnt-Dvl-3-β-catenin signaling.

Recurrent and hormone-refractory prostate cancer (PCA) exhibits aggressive behaviors while current therapeutic approaches show little effect of prolonging the survival of patients with PCA. Thus, a deeper understanding of the patho-molecular mechanisms underlying the disease progression in PCA is crucial to identify novel diagnostic and/or therapeutic targets to improve the outcome of patients. Recent evidence suggests that activation of Wnt signaling in cancer stem cells (CSCs) contributes to cancer progression in malignant tumors. Here, we report that a novel Wnt co-activator ASPM (abnormal spindle-like microcephaly associated) maintains the prostate CSC subpopulation by augmenting the Wnt-β-catenin signaling in PCA. ASPM expression is incrementally upregulated in primary and metastatic PCA, implicating its potential role in PCA progression. Consistently, downregulation of ASPM expression pronouncedly attenuated the proliferation, colony formation, and the invasive behavior of PCA cells, and dramatically reduced the number of ALDH+ CSCs and inhibited cancer stemness and tumorigenicity. Mechanistically, ASPM interacts with disheveled-3 (Dvl-3), a cardinal upstream regulator of canonical Wnt signaling, and inhibits its proteasome-dependent degradation, thereby increasing its protein stability and enabling the Wnt-induced β-catenin transcriptional activity in PCA cells. In keeping with the role of ASPM as a CSC-regulator, ASPM co-localizes with ALDH in PCA tissues and its expression exhibits high intra-tumoral heterogeneity. The proportion of high-ASPM-expressing cells in the tumor inversely correlates with the relapse-free survival of PCA patients. Collectively, our data points to ASPM as a novel oncoprotein and an essential regulator of Wnt signaling and cancer stemness in PCA, which has important clinical and therapeutic significance.

Lipopolysaccharide (LPS) enhances prostate cancer metastasis potentially through NF-κB activation and recurrent dexamethasone administration fails to suppress it in vivo.

Previous studies have shown the effect of bacterial lipopolysaccharide (LPS) on enhanced cancer cells' growth and metastasis. However, the effect of LPS on prostate cancer (PCa) cells metastasis has not been investigated in details. This study aimed to investigate the functional role of LPS on PCa cells metastasis and determine the effect of dexamethasone (DEX) on this event. Two different PCa reporter cells lines (DU145-NF-κB-Luc and MAT-LyLu- NF-κB-Luc) were used to assess the direct effect of LPS on NF-κB activation in PCa cells. Plasma collected from LPS-stimulated human and rodent blood were used to check the indirect effect of LPS on NF-κB activation in PCa cells. Trans-well migration assay and two different orthotopic PCa animal models were used to investigate the effect of LPS on DU145 and MAT-LyLu cells migration or metastasis in vitro and in vivo, respectively. In all the studies DEX was used with or without LPS stimulation. LPS and secretory factors present in plasma collected from LPS-stimulated blood, significantly activated NF-κB in DU145, and MAT-LyLu cells and enhanced their migration in vitro. DEX significantly suppressed LPS-mediated activation of cancer and blood cells and abrogated the direct and indirect pro-migratory effect of LPS on PCa cells. Systemic administration of LPS activated NF-κB in DU145 cells in vivo; however, failed to alter the metastatic properties of these cells. On the other hand, systemic administration of LPS to MAT-LyLu tumor bearing animals significantly enhanced the incidence of metastasis without altering the overall growth of primary tumors. Unexpectedly, though DEX significantly suppressed MAT-LyLu primary tumor weights, it aggravated metastasis of cancer cells in presence and absence of LPS. Moreover, consecutive DEX pre-treatment enhanced experimental peritoneal metastasis of MAT-LyLu cells. At the molecular level, LPS, and/or DEX induced overexpression of immunosuppressive molecules in MAT-LyLu tumors. Overall, our study has shown that LPS and/or LPS induced inflammation can increase PCa metastasis and immunosuppressive dose of DEX might further enhance cancer metastasis.

Abstract A026: Expression of fibroblast growth factor receptor 1 isoforms and activation of different pathways in prostate cancer progression

Abstract Bone metastases typically develop in patients with advanced prostate cancer (PCa). Androgen deprivation is commonly used as treatment, but responses are short, and eventually the disease progresses to a castration-resistant form (CRPC). The fibroblast growth factor (FGF) axis is commonly altered during PCa progression. Our group and others have implicated the FGF axis in the pathogenesis of PCa progression in bone, identified it as a candidate target for therapy, and suggested that FGF receptor (FGFR)-1 mediates a positive feedback loop between PCa cells and bone cells. RNA sequencing studies of 183 human PCa samples indicated that the mean expression of FGFR-1 is the highest of all the FGFR family genes studied. Analyses of these FGFR-1 transcripts identified eight different protein-coding transcripts to be the most abundantly expressed with diverse human PCa tissue samples expressing different FGFR-1 isoforms. The overall goal of this project is to investigate implications of FGFR1/FGFR1 isoforms expression in the pathogenesis of PCa bone metastases. When we assessed the expression of the two best-characterized FGFR-1 isoforms (alpha (NM_023110.2) and beta (NM_023105.2), which represent the most abundant protein coding transcripts found in PCa, we observed that all patient-derived xenografts (PDXs) studied express significantly higher levels of FGFR-1 alpha than beta while PCa cell lines mostly express the beta isoform. Mining The Cancer Genome Atlas (TCGA) PCa data, we identified distinct patterns of gene expression associated with each FGFR-1 isoform (alpha and beta). Briefly, FGFR-1 beta (but not alpha) is significantly associated with pathways including the MAP-kinase signaling cascade, signaling by FGFR in disease and pathways in cancer. In vitro studies of FGF signaling activation in PCa cells expressing FGFR-1 isoforms alpha, beta or empty vector, confirmed these results. Male SCID mice injected intracardially with PC3-FGFR-1 alpha exhibited higher death rates compared to animals injected with either PC3-FGFR-1 beta or PC3-empty vector. Furthermore, higher number of metastases per mice as well as higher number of mice with bone metastases were observed in animals injected with PC3-FGFR-1 alpha. The fact that different prostate tumors express different FGFR-1 isoforms suggests that FGFR1 alpha and beta isoforms activate different genes or pathways in PCa cells and this may underlie, at least in part, PCa heterogeneity, pattern of progression, and differences in response to FGFR1 inhibitors. Further studies will warrant the understanding of the implications of FGFR-1 isoforms expression in the pathogenesis of PCa. Citation Format: Estefania Labanca, Jun Yang, Peter Shepherd, Justin Roberts, Michael Starbuck, Bradley Broom, Matthew Iyer, Christopher Logothetis, Arul Chinnaiyan, Nora Navone. Expression of fibroblast growth factor receptor 1 isoforms and activation of different pathways in prostate cancer 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 A026.

Abstract 4485: VGLL3 is a novel outlier in African American prostate tumors and its expression is associated with a tumor suppressor phenotype in prostate cancer

Abstract Higher incidence, progression and mortality of prostate cancer (PCa) have been noted in African American (AA) men compared with Caucasian (CA) men. In fact AA race is an independent predictor of biochemical recurrence for all stage of PCa (Dr. Schaeffer's data analysis, n=1634 of AA patients). The etiology of PCa racial disparities is likely multi-factorial with increasing support of biologic contributors to these differences. By analyzing large cohort of PCa, we have demonstrated that AA PCa exhibits a unique spectrum of molecular subtypes. For example, AA men presented with PCa have a significant decrease in fusion proteins such as ERG, ETS and SPINK, with an enrichment of fusion unknown (FU; triple negative) cases. Given the increased mortality of PCa in AA populations and the enrichment of FU cases among AA tumors, there is an urgent need to define and explore individual outlier as race-based modifiers of disease aggressiveness. By utilizing a large multi-institutional cohort of prostate cancer cases of mixed racial composition, we have identified novel outliers enriched in AA among FU group by COPA outlier analysis.VGLL3 is one of the top outliers enriched in AA. VGLL3 positive cases are associated with low stage (less LNI, p=0.001; SVI, p<0.001; and EPE, p=0.009) and low grade disease (less Gleason >7, p=0.012) of higher protective phenotype of adverse cancer grade and stage. This preliminary work on VGLL3 expression suggests it may be associated with a tumor suppressor-like phenotype with reductions in expression with increasingly aggressive PCa. Studies of VGLL3 in cancer are limited and the role of VGLL3 in prostate has not been explored at all. The goal of this study is to investigate the role of VGLL3 as a novel outlier in AA prostate cancer that modulates disease aggressiveness. We found that mRNA expression levels of VGLL3 were lower in prostate cancer epithelial cells than in normal epithelial cells or stromal cells. By establishing and characterizing PCa models overexpressing VGLL3 in vitro and in vivo, our data demonstrate that VGLL3 significantly reduced migration and invasion of PCa cells and inhibited primary tumor cell growth. Our preliminary data also indicate VGLL3 inhibits PCa metastasis. Furthermore, VGLL3 seems to negatively affect both hippo and AR activity in PCa cells and these might be the mechanisms that VGLL3 inhibits tumor cell growth. These data is consistent with our clinical data suggesting tumor suppressive role of VGLL3 in advanced PCa. Citation Format: Hongjun Kang. VGLL3 is a novel outlier in African American prostate tumors and its expression is associated with a tumor suppressor phenotype in prostate cancer [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 4485.

Abstract 538: ASPM promotes prostate cancer tumorigenesis by bolstering cancer stemness through Wnt-Dvl-3-b-catenin signaling

Abstract Metastasis is the major cause of cancer mortality in androgen-independent prostate cancer (PCA) and understanding it is crucial to improving the outcome of patients. Recent evidence suggests that activation of Wnt signaling in cancer stem cells (CSCs) contributes to cancer progression in malignant tumors. Here we report that a novel Wnt activator ASPM (Abnormal spindle-like microcephaly associated) maintains the prostate CSC subpopulation through augmenting the Wnt-β-catenin signaling in PCA. Functional studies showed that downregulation of ASPM expression attenuated the proliferation and invasive of PCA cells and reduced the number of prostate CSCs and inhibited cancer stemness and tumorigenesis. Mechanistically, ASPM interacts with dishevelled-3 (Dvl-3) and inhibits its proteasome-dependent degradation, thereby increasing the protein stability of Dvl-3 and enabling the β-catenin transcriptional activity in PCA cells. The clinical significance of the above findings was credentialed by the profound up-regulation of ASPM in metastatic PCA and the strong correlation of cytoplasmic ASPM expression with poor metastasis-free survival of patients with resected PCA. Collectively, our data points to ASPM as a novel oncoprotein and an essential regulator of cancer stemness in PCA, which has important clinical and therapeutic significance (supported by Ministry of Science and Technology grants MOST 104-2314-B-400-022 and MOST 105-2314-B-400-018 and National Health Research Institutes NHRIs grant CA-106-PP-09 to K.K.T). Citation Format: Kelvin K. Tsai, Vincent C. Pai, Chung-Chi Hsu, Tze-Sian Chan. ASPM promotes prostate cancer tumorigenesis by bolstering cancer stemness through Wnt-Dvl-3-b-catenin signaling [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 538.

Identification of an IL‐1‐induced gene expression pattern in AR+ PCa cells that mimics the molecular phenotype of AR− PCa cells

In immunosurveillance, bone-derived immune cells infiltrate the tumor and secrete inflammatory cytokines to destroy cancer cells. However, cancer cells have evolved mechanisms to usurp inflammatory cytokines to promote tumor progression. In particular, the inflammatory cytokine, interleukin-1 (IL-1), is elevated in prostate cancer (PCa) patient tissue and serum, and promotes PCa bone metastasis. IL-1 also represses androgen receptor (AR) accumulation and activity in PCa cells, yet the cells remain viable and tumorigenic; suggesting that IL-1 may also contribute to AR-targeted therapy resistance. Furthermore, IL-1 and AR protein levels negatively correlate in PCa tumor cells. Taken together, we hypothesize that IL-1 reprograms AR positive (AR+ ) PCa cells into AR negative (AR- ) PCa cells that co-opt IL-1 signaling to ensure AR-independent survival and tumor progression in the inflammatory tumor microenvironment. LNCaP and PC3 PCa cells were treated with IL-1β or HS-5 bone marrow stromal cell (BMSC) conditioned medium and analyzed by RNA sequencing and RT-QPCR. To verify genes identified by RNA sequencing, LNCaP, MDA-PCa-2b, PC3, and DU145 PCa cell lines were treated with the IL-1 family members, IL-1α or IL-1β, or exposed to HS-5 BMSC in the presence or absence of Interleukin-1 Receptor Antagonist (IL-1RA). Treated cells were analyzed by western blot and/or RT-QPCR. Comparative analysis of sequencing data from the AR+ LNCaP PCa cell line versus the AR- PC3 PCa cell line reveals an IL-1-conferred gene suite in LNCaP cells that is constitutive in PC3 cells. Bioinformatics analysis of the IL-1 regulated gene suite revealed that inflammatory and immune response pathways are primarily elicited; likely facilitating PCa cell survival and tumorigenicity in an inflammatory tumor microenvironment. Our data supports that IL-1 reprograms AR+ PCa cells to mimic AR- PCa gene expression patterns that favor AR-targeted treatment resistance and cell survival.

Non-canonical activation of hedgehog in prostate cancer cells mediated by the interaction of transcriptionally active androgen receptor proteins with Gli3

Hedgehog (Hh) is an oncogenic signaling pathway that regulates the activity of Gli transcription factors. Canonical Hh is a Smoothened- (Smo-) driven process that alters the post-translational processing of Gli2/Gli3 proteins. Though evidence supports a role for Gli action in prostate cancer (PCa) cell growth and progression, there is little indication that Smo is involved. Here we describe a non-canonical means for activation of Gli transcription in PCa cells mediated by the binding of transcriptionally-active androgen receptors (ARs) to Gli3. Androgens stimulated reporter expression from a Gli-dependent promoter in a variety of AR + PCa cells and this activity was suppressed by an anti-androgen, Enz, or by AR knockdown. Androgens also upregulated expression of endogenous Gli-dependent genes. This activity was associated with increased intranuclear binding of Gli3 to AR that was antagonized by Enz. Fine mapping of the AR binding domain on Gli2 showed that AR recognizes the Gli protein processing domain (PPD) in the C-terminus. Mutations in the arginine-/serine repeat elements of the Gli2 PPD involved in phosphorylation and ubiquitinylation blocked the binding to AR. β-TrCP, a ubiquitin ligase that recognizes the Gli PPD, competed with AR for binding to this site. AR binding to Gli3 suppressed its proteolytic processing to the Gli3 repressor form (Gli3R) whereas AR knockdown increased Gli3R. Both full-length and truncated ARs were able to activate Gli transcription. Finally, we found that an ARbinding decoy polypeptide derived from the Gli2 C-terminus can compete with Gli3 for binding to AR. Exogenous overexpression of this decoy suppressed Gli transcriptional activity in PCa cells. Collectively, this work identifies a novel pathway for non-canonical activation of Hh signaling in PCa cells and identifies a means for interference that may have clinical relevance for PCa patients.

Punicalagin, a polyphenol from pomegranate fruit, induces growth inhibition and apoptosis in human PC-3 and LNCaP cells

Prostate cancer (PCa) is an international health problem and search for its effective treatment is in progress. Punicalagin (PN), polyphenol from pomegranate fruit, is known to exhibit potent anticancer activity in lung, breast and cervical cells. However, there is paucity of information on its effect in PCa. This study evaluated anti-proliferative effects of PN and its effects on extrinsic pathway of apoptosis in PCa cells, and angiogenesis in chicken chorioallantoic membrane (CAM). Antioxidant activities of PN were determined by 2,2–diphenyl-1-picryhydrazyl (DPPH) radical scavenging and inhibition of lipid peroxidation (LPO) methods. PCa (PC-3 and LNCaP) and normal prostate (BPH-1) cells were cultured and treated with PN (10, 50 and 100 μM). Cytotoxicity and viability effects of PN were determined by lactate dehydrogenase (LDH) and XTT assays, respectively. Antiangiogenic effects were measured using CAM assay, while apoptosis was assessed by DNA fragmentation, enrichment factor by Cell Death Detection ELISA kit and expressions of caspases-3 and -8. Results showed that PN (10–200 μM) significantly scavenged DPPH and inhibited LPO in a concentration-dependent manner. Furthermore, PN (10–100 μM) concentration-dependently inhibited viability in PC-3 and LNCaP, while viability in BPH-1 was insignificantly affected. PN had low toxicity on cells in vitro at concentrations tested. Also, PN (100 μM) increased enrichment factor in PC-3 (2.34 ± 0.05) and LNCaP (2.31 ± 0.26) relative to control (1.00 ± 0.00). In addition, PN (50 μM) decreased the network of vessels in CAM, suggesting its anti-angiogenic effect. Moreso, PN increased the expressions of caspases-3 and -8 in PC-3. Overall, PN exerts anti-proliferative activity in PCa cells via induction of apoptosis and anti-angiogenic effect.

Abstract 3525: PDEF promote prostate cancer luminal/epithelial differentiation and inhibit tumor progression

Abstract Conventional therapies produce a high rate of cure for patients with localized prostate cancer (PCa), but there is no effective treatment for castration resistant metastatic PCa. Transcription factors by association with enhancer and super-enhancer elements are key drivers of cell identity. Our previous studies have shown that Sam Pointed Domain Ets Transcription Factor a.k.a. Prostate Derived Ets Factor (SPDEF/PDEF), inhibits cell migration, invasion and clonogenic activity in PCa cells and there is a graded loss of PDEF with increasing Gleason Score in PCa patient samples. PDEF has been reported to be one of the cell identity transcription factors in LNCaP cells. We proposed that PDEF functions as a putative tumor metastasis suppressor. Others have shown an increase in Twist1, a bHLH transcription factor, was positively correlated with Gleason Grading. Present study was designed to investigate the role of PDEF and interplay between PDEF and Twist1 in PCa. PC3 cells were stably transfected with PDEF/control PABABE vectors. Gene expression changes were monitored by Affymetrix microarray. Microarray was analyzed with GSEA. qRT-PCR was performed to confirm gene expression and IHC, IF and IB analysis were performed to visualize protein expression. Chip-seq data (SRP002475) was aligned with Bowtie. Peaks were identified by MACS and visualized using IGB. PDEF/Twist1 expression data was extracted from GSE16560. GraphPad was used to generate KM survival analysis of PCa patients. Our results show that PDEF expression is limited to epithelial/luminal cells of the prostatic glands. We observed that expression of Twist1 was down regulated in PC3 cells following PDEF expression. Analysis of gene expression data from our microarray studies revealed that PDEF re-expression was associated with negative enrichment of gene sets involved with cell migration and positive enriched of gene sets involved with epithelial/luminal differentiation. Chip-seq analysis revealed a binding of PDEF to KRT8/18 promoter region. These data suggest that PDEF inhibits core metastasis related genes through promoting a program of luminal/epithelial differentiation. In clinical samples of PCa, expression of PDEF was inversely associated, while expression of Twist1 was positively associated with Gleason grade. PDEF and Twist1 was able to predict patient survival, moreover integrated PDEF and Twist1 expression was able to better predict PCa patient survival as compared to PDEF or Twist1 alone. PDEF inhibits cell migration and metastasis in part by down-regulating Twist1 level and promoting luminal/epithelial differentiation. Loss of PDEF combined with gain of Twist1 expression may serve as a potential biomarker set for distinguishing lethal PCa from an indolent disease. Additional studies are underway to gain further insights into the role of PDEF in PCa progression and metastasis. Acknowledgement: FWCC support and Chair commitment funds (Koul H). Citation Format: Fengtian Wang, Sweaty Koul, Prakash Srinivasan Timiri Shanmugam, Qin Dong, Hari K. Koul. PDEF promote prostate cancer luminal/epithelial differentiation and inhibit tumor progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3525. doi:10.1158/1538-7445.AM2017-3525

Antioxidant and antiproliferative potentials of methanol extract of Xylopia aethiopica (Dunal) A. Rich in PC-3 and LNCaP cells.

Our previous studies showed that fruit methanol extract from Xylopia aethiopica (MEXA) exhibited antiproliferative activity in human cervical cancer cells via the induction of apoptosis. The present study was designed to assess the antiproliferative, antiangiogenic and antioxidant effects of MEXA on prostate cancer (PCa) cells (PC-3 and LNCaP). PC-3 and LNCaP cells were cultured and treated with MEXA (10, 50 and 100 μg/mL). The sodium 3'-[1-(phenylaminocarbonyl)-3,4-tetrazolium]-bis (4-methoxy-6-nitro) benzene sulfonic acid hydrate (XTT) and lactate dehydrogenase (LDH) assays were used to evaluate cell viability and cytotoxicity, respectively. DNA fragmentation was determined by cell death detection ELISA plus, and angiogenesis was assessed by chicken chorioallantoic membrane (CAM) assay. The antioxidant activities of MEXA were determined by DPPH and hydroxyl (OH) radicals' scavenging methods as well as through the inhibition of lipid peroxidation (LPO) in rats' liver homogenate. MEXA at 100, 250 and 500 μg/mL scavenged DPPH by 48%, 62%, 70% and OH radical by 39%, 58%, 67%, respectively. MEXA significantly (p<0.05) inhibited LPO in a concentration-dependent manner. In addition, MEXA had antiproliferative effects on PC-3 and LNCaP with IC50 of 62.1 and 73.6 μg/mL, respectively, at 96 h. The LDH assay showed that MEXA had low toxicity in vitro at its IC50 values. The extent of DNA fragmentation by MEXA showed higher values in PC-3 and LNCaP, suggesting the possible induction of apoptosis. In contrast, MEXA did not affect the network of vessels in CAM, thus lacking anti-angiogenic property. These findings suggest that MEXA induces antiproliferative activity in PCa cells through a mechanism that involves apoptosis. Therefore, MEXA may be a potential therapeutic agent for PCa.

PD33-01 NON-CANONICAL ACTIVATION OF HEDGEHOG SIGNALING IN PROSTATE CANCER CELLS MEDIATED BY THE BINDING OF TRANSCRIPTIONALLY ACTIVE ANDROGEN RECEPTORS TO GLI TRANSCRIPTION FACTORS

You have accessJournal of UrologyProstate Cancer: Basic Research & Pathophysiology I1 Apr 2017PD33-01 NON-CANONICAL ACTIVATION OF HEDGEHOG SIGNALING IN PROSTATE CANCER CELLS MEDIATED BY THE BINDING OF TRANSCRIPTIONALLY ACTIVE ANDROGEN RECEPTORS TO GLI TRANSCRIPTION FACTORS Na Li, Sarah Truong, Mannan Nouri, Amy Anne Lubik, and Ralph Buttyan Na LiNa Li More articles by this author , Sarah TruongSarah Truong More articles by this author , Mannan NouriMannan Nouri More articles by this author , Amy Anne LubikAmy Anne Lubik More articles by this author , and Ralph ButtyanRalph Buttyan More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.3315AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Canonical (smoothened-driven) Hedgehog signaling regulates the activities of Gli transcription factors and their ability to induce cell proliferation, motility and invasion. While there are numerous reports of constitutive Hedgehog/Gli activity in prostate cancer (PCa) cells, there is little evidence for a role of smoothened in this activity. Previously we showed that Gli proteins bind to full length- (FL-) and truncated- (t-) androgen receptors (ARs) at the N-terminal tau5 transactivation domain and that this binding co-activates AR transcriptional activity in PCa cells. Here we show, conversely, that transcriptionally active AR binds to a critical protein processing domain on Gli2/Gli3, alters their post-translational proteolytic processing and drives non-canonical Hedgehog signaling that facilitates androgen-independent growth of PCa cells. METHODS Site-specific mutations were introduced into the Gli2 C-terminal domain to identify the peptides involved in AR recognition. GST-pulldown was used to test binding of the mutated peptide to AR-tau5 peptide. Western blotting was used to quantify AR expression and the proteolytic states of Gli2 and 3 in LNCaP, LNCaP-AI, LN95 and VCaP cells. AR or Gli3 protein was knocked down with siRNAs. A Gli-luciferase reporter was used to measure functional Gli activity in cells and qPCR was used to determine how AR or Gli expression manipulation affected expressions of endogenous Gli-responsive genes. Proximity ligation assays with antibodies against AR and Gli3 was used to quantify the relative binding of these proteins in androgen-dependent and androgen-independent cell lines. RESULTS Mutations in a repeat serine/arginine-rich peptide in the C-terminal domain of Gli2 (aa820-836) blocked Gli2 binding to AR. This peptide encompasses the Gli protein processing domain that regulates a site-specific proteolysis that renders transcriptionally active Gli proteins into transcriptional repressors. Binding of liganded AR to this site blocked Gli proteolysis and maintained Gli in transcriptionally active states. Knockdown of AR in androgen growth-independent cell lines induced proteolytic inactivation of Gli in PCa cells. Knockdown of Gli3 in these cells induced a loss of AR protein. Proximity ligation assays showed that binding between Gli3 and AR was higher in androgen-independent cell lines. CONCLUSIONS Transcriptionally active AR protein binding to Gli proteins protects both from a natural degradation process and provides a non-canonical means to activate Hedgehog signaling in PCa cells. Since Gli proteins regulate the expressions of growth-promoting genes, our findings suggest that the growth effects of androgens on PCa cells are the results of a non-canonical Hedgehog activation process. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e593 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Na Li More articles by this author Sarah Truong More articles by this author Mannan Nouri More articles by this author Amy Anne Lubik More articles by this author Ralph Buttyan More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Abstract 5263: Prostate-specific membrane antigen (PSMA)-targeting nanobioconjugate-encapsulated green tea polyphenol EGCG for prostate cancer prevention and therapy

Abstract Initially we introduced the idea of employing nanotechnology to improve the outcome of natural agents in chemoprevention and coined the term ‘Nanochemoprevention’. Recently we reported the efficacy of chitosan nanoparticles encapsulating (-)-epigallocatechin-3-gallate (EGCG) for prostate cancer (PCa) prevention and therapy. Here we employed the concept of targeted uptake of therapeutic nanoparticles, a potentially powerful technology to enhance the efficacy of EGCG for PCa management. We developed chitosan nanobioconjugates encapsulating EGCG and surface functionalized with the A10 2′-fluoropyrimidine RNA aptamers that recognize the extracellular domain of the PSMA, henceforth called chit-EGCG-Apt. Cellular binding and uptake of the fluorescent nanosystem was detected suggesting PSMA specific internalization and accumulation. Further, we observed that chit-EGCG-Apt lead to a PSMA specific increase of anti-proliferative activity in PCa cells, with a better efficacy in PSMA positive cells (LNCaP and C4-2) than in PSMA negative (PC3 and DU145) cells and a decrease in IC50 by at least half the dose of the native agent. Further, we also observed a significant inhibition in the colony formation potency of PCa cells when treated with chit-EGCG-Apt as compared to the native EGCG with the effects more distinct in PSMA positive cells. Next, we established that EGCG in chit-EGCG-Apt retains its mechanistic identity and observed that the treatment resulted in significant (i) shift in Bax/Bcl-2 ratio in favor of apoptosis, (ii) increase in PARP cleavage, (iii) inhibition in caspase 3, 7, 8 and 9, and other key regulators of apoptosis, (iv) modulation of death receptor pathway proteins, and (v) cyclin dependent kinase inhibitors in addition to arrest of the cells in S phase of the cell cycle. Importantly, these effects were only visible at higher doses of the native EGCG. The nanobioconjugate also demonstrated a significant inhibition of invasive potential of several PCa cells and 3-dimensional spheroid BME cell invasion assay. Further, chit-EGCG-Apt treated mice implanted with androgen sensitive CWR22R(nu)1 cells showed significant inhibition in tumor growth and decreased serum PSA levels reciprocating our in vitro findings. In tumor tissues of mice treated with Chit-EGCG-Apt there was significant (i) induction of poly (ADP-ribose) polymerases cleavage, (ii) increase in the protein expression of Bax with concomitant decrease in Bcl-2, (iii) activation of caspases, and (iv) reduction in Ki-67 and proliferating cell nuclear antigen, as compared to native EGCG. We further observed inhibition of angiogenesis, invasion and metastasis markers in these tissues. Translation of these data to appropriate animal model systems could pave way for prostate cancer therapy in humans. Citation Format: Imtiaz A. Siddiqui, Dhruba J. Bharali, Rahime Jashari, Vaqar M. Adhami, Shaker A. Mousa, Hasan Mukhtar. Prostate-specific membrane antigen (PSMA)-targeting nanobioconjugate-encapsulated green tea polyphenol EGCG for prostate cancer prevention and therapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5263.

Dual tumor suppressing and promoting function of Notch1 signaling in human prostate cancer.

Adenocarcinomas of the prostate arise as multifocal heterogeneous lesions as the likely result of genetic and epigenetic alterations and deranged cell-cell communication. Notch signaling is an important form of intercellular communication with a role in growth/differentiation control and tumorigenesis. Contrasting reports exist in the literature on the role of this pathway in prostate cancer (PCa) development. We show here that i) compared to normal prostate tissue, Notch1 expression is significantly reduced in a substantial fraction of human PCas while it is unaffected or even increased in others; ii) acute Notch activation both inhibits and induces process networks associated with prostatic neoplasms; iii) down-modulation of Notch1 expression and activity in immortalized normal prostate epithelial cells increases their proliferation potential, while increased Notch1 activity in PCa cells suppresses growth and tumorigenicity through a Smad3-dependent mechanism involving p21WAF1/CIP1; iv) prostate cancer cells resistant to Notch growth inhibitory effects retain Notch1-induced upregulation of pro-oncogenic genes, like EPAS1 and CXCL6, also overexpressed in human PCas with high Notch1 levels. Taken together, these results reconcile conflicting data on the role of Notch1 in prostate cancer.

Reciprocal regulation of GAS5 lncRNA levels and mTOR inhibitor action in prostate cancer cells.

New therapies are required for castrate-resistant prostate cancer (CRPC), and growth-arrest specific 5 (GAS5) lncRNA, which riborepresses androgen receptor action, may offer novel opportunities in this regard. This lncRNA promotes the apoptosis of prostate cancer cells and its levels decline as prostate cancer cells acquire castrate-resistance, so that enhancing GAS5 expression may improve the effectiveness of chemotherapies. Since GAS5 is a member of the 5' terminal oligopyrimidine gene family, we have examined mTOR inhibition as a strategy to increase GAS5 expression. Furthermore, we have determined if GAS5 itself mediates the action of mTOR inhibitors, as demonstrated for other chemotherapeutic agents in prostate cancer cells. The effects of mTOR inhibitors on GAS5 lncRNA levels and cell growth were determined in a range of prostate cancer cell lines. Transfection of cells with GAS5 siRNAs and plasmid constructs was performed to determine the involvement of GAS5 lncRNA in mTOR inhibitor action. First generation mTORC1, combined mTORC1/mTORC2 and dual PI3K/mTOR inhibitors all increased cellular GAS5 levels and inhibited culture growth in androgen-dependent (LNCaP) and androgen-sensitive (22Rv1) cell lines, but not in androgen-independent (PC-3 and DU 145) cell lines. The latter exhibited low endogenous GAS5 expression, and GAS5 silencing in LNCaP and 22Rv1 cells decreased the sensitivity to mTOR inhibitors, whereas transfection of GAS5 lncRNA sensitized PC-3 and DU 145 cells to these agents. mTOR inhibition enhances GAS5 transcript levels in certain prostate cancer cell lines. This selectivity is likely to be related to endogenous GAS5 expression levels, since GAS5 lncRNA is itself required for mTOR inhibitor action in prostate cancer cells.

Abstract 251: Aptamer conjugated prostate specific membrane antigen (PSMA) targeting EGCG nanobioconjugate for prostate cancer prevention and treatment

Abstract Earlier we introduced the idea of employing nanotechnology to improve the outcome of natural agents in chemoprevention and coined the term ‘Nanochemoprevention’. Recently we reported the efficacy of chitosan nanoparticles encapsulating green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG) for prostate cancer (PCa) therapy. Here we employed the idea of targeted uptake of therapeutic nanoparticles, a potentially powerful technology. Using PCa as a model, we report the efficacy of EGCG encapsulated in chitosan nanoparticles surface functionalized with the A10 2′-fluoropyrimidine RNA aptamers that recognize the extracellular domain of the prostate-specific membrane antigen (PSMA), henceforth called chit-EGCG-Apt. Prepared bioconjugates were spherical in shape with a unimodal size distribution, with diameter around 200 nm and a zeta potential of -30 mV. Cellular binding and uptake of the fluorescent nanosystem was detected suggesting PSMA specific internalization and accumulation. Next, we determined the EGCG release kinetics and observed a sustained and constant release of EGCG from the nanobioconjugates. To test the biological efficacy, we first determined the efficacy of chit-EGCG-Apt for its cytotoxic response in several human prostate carcinoma cells. We observed that chit-EGCG-Apt lead to an increased anti-proliferative activity in PCa cells, with a better efficacy in PSMA positive cells (LNCaP and C4-2) than in PSMA negative PC3 cells and a decrease in IC50 by at least half the dose of the native agent. Further, we also observed a significant inhibition in the colony formation potency of PCa cells when treated with chit-EGCG-Apt as compared to the native EGCG with the effects more distinct in PSMA positive cells. Our next goal was to ascertain if EGCG in chit-EGCG-Apt retains its mechanistic identity. Chit-EGCG-Apt treatment (10 and 20 μM) to LNCaP cells resulted in significant (i) shift in Bax/Bcl-2 ratio in favor of apoptosis, (ii) increase in PARP cleavage, (iii) inhibition in caspase 3, 7, 8 and 9, and other key regulators of apoptosis, (iv) modulation of DR4, DR5, TNFR1, FADD, TRADD death receptor pathway proteins, (v) increase in the levels of annexin V positive cells, (vi) increase in TdT positive cells (additional information to suggest induction of apoptosis), and (vii) modulation of p21, p27, CDK 4 and 6 cyclin dependent kinase inhibitors in addition to arrest of the cells in S phase of the cell cycle. Importantly, these effects were only visible at 40 μM of the native EGCG. The nanobioconjugate also demonstrated a significant inhibition of invasive potential of several PCa cells in scratch wound assay and 3-dimensional spheroid BME cell invasion assay. Translation of these data to appropriate animal model systems could pave way for prostate cancer therapy in humans. Citation Format: Imtiaz A. Siddiqui, Dhruba J. Bharali, Minakshi Nihal, Vaqar M. Adhami, Rahime Jashari, Shaker A. Mousa, Hasan Mukhtar. Aptamer conjugated prostate specific membrane antigen (PSMA) targeting EGCG nanobioconjugate for prostate cancer prevention and treatment. [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 251. doi:10.1158/1538-7445.AM2014-251

A therapeutic approach to treat prostate cancer by targeting Nm23-H1/h-Prune interaction.

Nm23-H1 is a metastasis suppressor gene whose overexpression is associated with both reduced cell motility in various cancers and increased metastatic potential in neuroblastomas, osteosarcomas, and hematological malignances. We previously reported that Nm23-H1 exerts tumor suppressor action in prostate cancer cells and that h-Prune, which is overexpressed in various tumor types, binds Nm23-H1. Moreover, blockage of the Nm23-H1/h-Prune interaction with a competitive permeable peptide (CPP) attenuates migration of breast and neuroblastoma cells. This series of events suggests that the Nm23-H1/h-Prune protein complex regulates cancer progression and that its specific impairment could be a new therapeutic strategy in oncology. We found that CPP leads to inhibition of the AKT/mTORv and NF-kBv signaling pathways and also activates apoptosis. To obtain a proof-of-concept of our hypothesis, we used a xenograft model of prostate cancer to evaluate whether impairment of this complex using CPP results in an anti-tumoral effect. Using a mouse orthotopic model with bioluminescent imaging, we show evidences that CPP reduces prostate cancer metastases formation. In conclusion, CPP being able to impair formation of the h-Prune/Nm23-H1 complex holds promise for the treatment of prostate cancer.

Loss of PTEN stabilizes the lipid modifying enzyme cytosolic phospholipase A₂α via AKT in prostate cancer cells.

Aberrant increase in pAKT, due to a gain-of-function mutation of PI3K or loss-of-function mutation or deletion of PTEN, occurs in prostate cancer and is associated with poor patient prognosis. Cytosolic phospholipase A₂α (cPLA₂α) is a lipid modifying enzyme by catalyzing the hydrolysis of membrane arachidonic acid. Arachidonic acid and its metabolites contribute to survival and proliferation of prostate cancer cells. We examined whether AKT plays a role in promoting cPLA₂α action in prostate cancer cells. We found a concordant increase in pAKT and cPLA₂α levels in prostate tissue of prostate epithelial-specific PTEN-knockout but not PTEN-wide type mice. Restoration of PTEN expression or inhibition of PI3K action decreased cPLA₂α expression in PTEN-mutated or deleted prostate cancer cells. An increase in AKT by Myr-AKT elevated cPLA₂α protein levels, which could be diminished by inhibition of AKT phosphorylation without noticeable change in total AKT levels. pAKT levels had no influence on cPLA₂α at mRNA levels but reduced cPLA₂α protein degradation. Anti-AKT antibody co-immunoprecipitated cPLA₂α and vice versa. Hence, AKT plays a role in enhancing cPLA₂α protein stability in PTEN-null prostate cancer cells, revealing a link between oncogenic pathway and lipid metabolism.