Repeated trans-arterial treatments of LDL-DHA nanoparticles induce multiple pathways of tumor cell death in hepatocellular carcinoma bearing rats

Introduction

Repeated hepatic arterial delivery of therapeutic agents to the liver by percutaneously implanted port-catheter systems has been widely used to treat unresectable liver cancer. This approach is applied to assess the therapeutic efficacy of repeated low-density lipoprotein-docosahexaenoic acid (LDL-DHA) nanoparticle treatments in a rat model of hepatocellular carcinoma.

Methods

N1S1 hepatoma bearing rats underwent placement of a percutaneously implanted hepatic artery port-catheter system and were allocated to untreated, control LDL-triolein (LDL-TO) or LDL-DHA nanoparticle infusions groups. Treatments were performed every three days over a nine day study period. MRI was performed at baseline and throughout the study. At the end of the study tissue samples were collected for analyses.

Results and Discussion

Implantation of the port catheters was successful in all rats. MRI showed that repeated infusions of LDL-DHA nanoparticles significantly impaired the growth of the rat hepatomas eventually leading to tumor regression. The tumors in the LDL-TO treated group showed delayed growth, while the untreated tumors grew steadily throughout the study. Histopathology and MRI support these findings demonstrating extensive tumor necrosis in LDL-DHA treated groups while the control groups displayed minor necrosis. Molecular and biochemical analyses also revealed that LDL-DHA treated tumors had increased levels of nuclear factor-kappa B and lipid peroxidation and depletion of glutathione peroxidase 4 relative to the control groups. Evidence of both ferroptosis and apoptosis tumor cell death was observed following LDL-DHA treatments. In conclusion repeated transarterial infusions of LDL-DHA nanoparticles provides sustained repression of tumor growth in a rat hepatoma model.

The helix-loop-helix transcriptional regulator Id4 is required for terminal differentiation of luminal epithelial cells in the prostate

Inhibitor of differentiation 4 (Id4), a member of the helix-loop-helix family of transcriptional regulators has emerged as a tumor suppressor in prostate cancer. In this study we investigated the effect of loss of Id4 (Id4-/-) on mouse prostate development. Histological analysis was performed on prostates from 25 days, 3 months and 6 months old Id4-/- mice. Expression of Amacr, Ck8, Ck18, Fkbp51, Fkbp52, androgen receptor, Pten, sca-1 and Nkx3.1 was investigated by immunohistochemistry. Results were compared to the prostates from Nkx3.1-/- mice. Id4-/- mice had smaller prostates with fewer and smaller tubules. Subtle PIN like lesions were observed at 6mo. Decreased Nkx3.1 and Pten and increased stem cell marker sca-1, PIN marker Amacr and basal cell marker p63 was observed at all ages. Persistent Ck8 and Ck18 expression suggested that loss of Id4 results in epithelial commitment but not terminal differentiation in spite of active Ar. Loss of Id4 attenuates normal prostate development and promotes hyperplasia/ dysplasia with PIN like lesions. The results suggest that loss of Id4 maintains stem cell phenotype of "luminal committed basal cells", identifying a unique prostate developmental pathway regulated by Id4.

Spermatogonial Gene Networks Selectively Couple to Glutathione and Pentose Phosphate Metabolism but Not Cysteine Biosynthesis

In adult males, spermatogonia maintain lifelong spermatozoa production for oocyte fertilization. To understand spermatogonial metabolism we compared gene profiles in rat spermatogonia to publicly available mouse, monkey, and human spermatogonial gene profiles. Interestingly, rat spermatogonia expressed metabolic control factors Foxa1, Foxa2, and Foxa3. Germline Foxa2 was enriched in Gfra1Hi and Gfra1Low undifferentiated A-single spermatogonia. Foxa2-bound loci in spermatogonial chromatin were overrepresented by conserved stemness genes (Dusp6, Gfra1, Etv5, Rest, Nanos2, Foxp1) that intersect bioinformatically with conserved glutathione/pentose phosphate metabolism genes (Tkt, Gss, Gc l c , Gc l m, Gpx1, Gpx4, Fth), marking elevated spermatogonial GSH:GSSG. Cystine-uptake and intracellular conversion to cysteine typically couple glutathione biosynthesis to pentose phosphate metabolism. Rat spermatogonia, curiously, displayed poor germline stem cell viability in cystine-containing media, and, like primate spermatogonia, exhibited reduced transsulfuration pathway markers. Exogenous cysteine, cysteine-like mercaptans, somatic testis cells, and ferroptosis inhibitors counteracted the cysteine-starvation-induced spermatogonial death and stimulated spermatogonial growth factor activity in vitro.

An implanted port-catheter system for repeated hepatic arterial infusion of low-density lipoprotein-docosahexaenoic acid nanoparticles in normal rats: A safety study

BACKGROUND

In recent years, small animal arterial port-catheter systems have been implemented in rodents with reasonable success. The aim of the current study is to employ the small animal port-catheter system to evaluate the safety of multiple hepatic-artery infusions (HAI) of low-density lipoprotein-docosahexaenoic acid (LDL-DHA) nanoparticles to the rat liver.

METHODS

Wistar rats underwent surgical placement of indwelling HAI ports. Repeated administrations of PBS or LDL-DHA nanoparticles were performed through the port at baseline and days 3 and 6. Rats were sacrificed on day 9 at which point blood and various organs were collected for histopathology and biochemical analyses.

RESULTS

The port-catheter systems were implanted successfully and repeated infusions of PBS or LDL-DHA nanoparticles were tolerated well by all animals over the duration of the study. Measurements of serum liver/renal function tests, glucose and lipid levels did not differ between control and LDL-DHA treated rats. The liver histology was unremarkable in the LDL-DHA treated rats and the expression of hepatic inflammatory regulators (NF-κβ, IL-6 and CRP) were similar to control rats. Repeated infusions of LDL-DHA nanoparticles did not alter liver glutathione content or the lipid profile in the treated rats. The DHA extracted by the liver was preferentially metabolized to the anti-inflammatory DHA-derived mediator, protectin DX.

CONCLUSION

Our findings indicate that repeated HAI of LDL-DHA nanoparticles is not only well tolerated and safe in the rat, but may also be protective to the liver.

Management of Hsp90-Dependent Protein Folding by Small Molecules Targeting the Aha1 Co-Chaperone

Hsp90 plays an important role in health and is a therapeutic target for managing misfolding disease. Compounds that disrupt co-chaperone delivery of clients to Hsp90 target a subset of Hsp90 activities, thereby minimizing the toxicity of pan-Hsp90 inhibitors. Here, we have identified SEW04784 as a first-in-class inhibitor of the Aha1-stimulated Hsp90 ATPase activity without inhibiting basal Hsp90 ATPase. Nuclear magnetic resonance analysis reveals that SEW84 binds to the C-terminal domain of Aha1 to weaken its asymmetric binding to Hsp90. Consistent with this observation, SEW84 blocks Aha1-dependent Hsp90 chaperoning activities, including the in vitro and in vivo refolding of firefly luciferase, and the transcriptional activity of the androgen receptor in cell-based models of prostate cancer and promotes the clearance of phosphorylated tau in cellular and tissue models of neurodegenerative tauopathy. We propose that SEW84 provides a novel lead scaffold for developing therapeutic approaches to treat proteostatic disease.

A Small-Molecule Pan-Id Antagonist Inhibits Pathologic Ocular Neovascularization

Id helix-loop-helix (HLH) proteins (Id1-4) bind E protein bHLH transcription factors, preventing them from forming active transcription complexes that drive changes in cell states. Id proteins are primarily expressed during development to inhibit differentiation, but they become re-expressed in adult tissues in diseases of the vasculature and cancer. We show that the genetic loss of Id1/Id3 reduces ocular neovascularization in mouse models of wet age-related macular degeneration (AMD) and retinopathy of prematurity (ROP). An in silico screen identifies AGX51, a small-molecule Id antagonist. AGX51 inhibits the Id1-E47 interaction, leading to ubiquitin-mediated degradation of Ids, cell growth arrest, and reduced viability. AGX51 is well-tolerated in mice and phenocopies the genetic loss of Id expression in AMD and ROP models by inhibiting retinal neovascularization. Thus, AGX51 is a first-in-class compound that antagonizes an interaction formerly considered undruggable and that may have utility in the management of multiple diseases.

Intra-tumoral delivery of functional ID4 protein via PCL/maltodextrin nano-particle inhibits prostate cancer growth

ID4, a helix loop helix transcriptional regulator has emerged as a tumor suppressor in prostate cancer. Epigenetic silencing of ID4 promotes prostate cancer whereas ectopic expression in prostate cancer cell lines blocks cancer phenotype. To directly investigate the anti-tumor property, full length human recombinant ID4 encapsulated in biodegradable Polycaprolactone/Maltodextrin (PCL-MD) nano-carrier was delivered to LNCaP cells in which the native ID4 was stably silenced (LNCaP(-)ID4). The cellular uptake of ID4 resulted in increased apoptosis, decreased proliferation and colony formation. Intratumoral delivery of PCL-MD ID4 into growing LNCaP(-)ID4 tumors in SCID mice significantly reduced the tumor volume compared to the tumors treated with chemotherapeutic Docetaxel. The study supports the feasibility of using nano-carrier encapsulated ID4 protein as a therapeutic. Mechanistically, ID4 may assimilate multiple regulatory pathways for example epigenetic re-programming, integration of multiple AR co-regulators or signaling pathways resulting in tumor suppressor activity of ID4.

Abstract 4975: A small molecule pan Id protein antagonist shows strong antitumor activity

The Id family of helix-loop-helix (HLH) proteins, Id1, Id2, Id3 and Id4, play a critical role in inhibiting differentiation during mammalian embryogenesis. They function in part by sequestering ubiquitously expressed E protein bHLH transcription factors via direct protein-protein interactions. Various Id proteins are re-expressed in adults in a number of pathologic states including cancer and diseases of the vasculature, where their activity has been shown to be essential for disease progression. The present study describes the solving of the Id1-E47 dimer crystal structure and subsequent development and characterization of a small molecule antagonist of the Id protein family, AGX51. AGX51 was identified in an in silico screen for compounds that could bind a hydrophobic crevice adjacent to the loop region of Id1, highly conserved in the Id family. AGX51 inhibits the endogenous Id1-E protein interaction leading to the degradation of Id1 via ubiquitin-mediated proteolysis. The stability of all four members of the Id family are antagonized by AGX51 leading to a G0-G1 arrest and profound inhibition of viability with no acquired resistance observed in multiple cell lines after continuous exposure to the compound. Administration of AGX51 is well tolerated in mice and phenocopies genetic loss of Id expression analyses: suppression of breast cancer metastases to the lung associated with a reduced mesenchymal-to-epithelial transition, perturbation of the vasculature within the primary tumor, and growth regression of paclitaxel resistant breast tumors in combination with paclitaxel therapy. These studies identify a novel, first-in-class compound capable of antagonizing the activity of a protein family formerly considered undruggable and point to the possible utility of AGX51 in the management of multiple disease processes in patients.

Citation Format: Paulina M. Wojnarowicz, Bina Desai, Yvette Chin, Sang Bae Lee, Marta Garcia-Cao, Ouathek Ouerfelli, Guangli Yang, Sijia Xu, Yehuda Goldgur, Meredith A. Miller, Jaideep Chaudhary, William A. Garland, Steven K. Albanese, Rajesh Soni, John Philip, Larry Norton, Neal Rosen, Ronald C. Hendrickson, Xi Kathy Zhou, Antonio Iavarone, Andrew J. Dannenberg, John D. Chodera, Nikola Pavletich, Anna Lasorella, Robert Benezra. A small molecule pan Id protein antagonist shows strong antitumor activity [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 4975. doi:10.1158/1538-7445.AM2017-4975

Inactivation of ID4 promotes a CRPC phenotype with constitutive AR activation through FKBP52

Castration-resistant prostate cancer (CRPC) is the emergence of prostate cancer cells that have adapted to the androgen-depleted environment of the prostate. In recent years, targeting multiple chaperones and co-chaperones (e.g., Hsp27, FKBP52) that promote androgen receptor (AR) signaling and/or novel AR regulatory mechanisms have emerged as promising alternative treatments for CRPC. We have shown that inactivation of inhibitor of differentiation 4 (ID4), a dominant-negative helix loop helix protein, promotes de novo steroidogenesis and CRPC with a gene expression signature that resembles constitutive AR activity in castrated mice. In this study, we investigated the underlying mechanism through which loss of ID4 potentiates AR signaling. Proteomic analysis between prostate cancer cell line LNCaP (L+ns) and LNCaP lacking ID4 (L(-)ID4) revealed elevated levels of Hsp27 and FKBP52, suggesting a role for these AR-associated co-chaperones in promoting constitutively active AR signaling in L(-)ID4 cells. Interestingly, protein interaction studies demonstrated a direct interaction between ID4 and the 52-kDa FK506-binding protein (FKBP52) in vitro, but not with AR. An increase in FKBP52-dependent AR transcriptional activity was observed in L(-)ID4 cells. Moreover, pharmacological inhibition of FKBP52-AR signaling, by treatment with MJC13, attenuated the tumor growth, weight, and volume in L(-)ID4 xenografts. Together, our results demonstrate that ID4 selectively regulates AR activity through direct interaction with FKBP52, and its loss, promotes CRPC through FKBP52-mediated AR signaling.

ID4 promotes AR expression and blocks tumorigenicity of PC3 prostate cancer cells

Deregulation of tumor suppressor genes is associated with tumorigenesis and the development of cancer. In prostate cancer, ID4 is epigenetically silenced and acts as a tumor suppressor. In normal prostate epithelial cells, ID4 collaborates with androgen receptor (AR) and p53 to exert its tumor suppressor activity. Previous studies have shown that ID4 promotes tumor suppressive function of AR whereas loss of ID4 results in tumor promoter activity of AR. Previous study from our lab showed that ectopic ID4 expression in DU145 attenuates proliferation and promotes AR expression suggesting that ID4 dependent AR activity is tumor suppressive. In this study, we examined the effect of ectopic expression of ID4 on highly malignant prostate cancer cell, PC3. Here we show that stable overexpression of ID4 in PC3 cells leads to increased apoptosis and decreased cell proliferation and migration. In addition, in vivo studies showed a decrease in tumor size and volume of ID4 overexpressing PC3 cells, in nude mice. At the molecular level, these changes were associated with increased androgen receptor (AR), p21, and AR dependent FKBP51 expression. At the mechanistic level, ID4 may regulate the expression or function of AR through specific but yet unknown AR co-regulators that may determine the final outcome of AR function.

A Modified Coupled Spectrophotometric Method to Detect 2-5 Oligoadenylate Synthetase Activity in Prostate Cell Lines

BACKGROUND

2'-5' oligoadenylate synthetases (OAS) are interferon inducible enzymes that polymerizes ATP to 2'-5'-linked oligomers of adenylate (2-5As). As part of the innate immune response, these enzymes are activated by viral double stranded RNA or mRNAs with significant double stranded structure. The 2-5As in turn activate RNaseL that degrade single stranded RNAs. Three distinct forms of OAS exist in human cells (OAS1, 2 and 3) with each form having multiple spliced variants. The OAS enzymes and their spliced variants have different enzyme activities. OAS enzymes also play a significant role in regulating multiple cellular processes such as proliferation and apoptosis. Moreover, Single nucleotide polymorphisms that alter OAS activity are also associated with viral infection, diabetes and cancer. Thus detection of OAS enzyme activity with a simple spectrophotometric method in cells will be important in clinical research.

RESULTS

Here we propose a modified coupled spectrophotometric assay to detect 2-5 oligoadenylate synthetase (OAS) enzyme activity in prostate cell lines as a model system. The OAS enzyme from prostate cancer cell lysates was purified using Polyinosinic: polycytidylic acid (poly I:C) bound activated sepharose beads. The activated OAS enzyme eluted from Sepharose beads showed expression of p46 isoform of OAS1, generally considered the most abundant OAS isoform in elutes from DU14 cell line but not in other prostate cell line. In this assay the phosphates generated by the OAS enzymatic reaction is coupled with conversion of the substrate 2-amino-6-mercapto-7-methylpurine ribonucleoside (methylthioguanosine, a guanosine analogue; MESG) to a purine base product, 2-amino-6-mercapto-7-methylpurine and ribose1-phosphate via a catalyst purine nucleoside phosphorylase (phosphorylase) using a commercially available pyrophosphate kit. The absorbance of the purine base product is measured at 360 nm. The higher levels of phosphates detected in DU145 cell line indicates more activity of OAS in this prostate cancer cell line.

CONCLUSION

The modified simple method detected OAS enzyme activity with sensitivity and specificity, which could help in detection of OAS enzymes avoiding the laborious and radioactive methods.

Relative Stability of Wild-Type and Mutant p53 Core Domain: A Molecular Dynamic Study

The p53 protein is a stress response protein that functions primarily as a tetrameric transcription factor. A tumor suppressor p53 binds to a specific DNA sequence and transactivates target genes, leading to cell cycle apoptosis. Encoded by the human gene TP53, p53 is a stress response protein that functions primarily as a tetrameric transcription factor. This gene regulates a large number of genes in response to a variety of cellular functions, including oncogene activation and DNA damage. Mutations in p53 are common in human cancer types. Herein we mutate a wild-type p53, 1TSR with four of its mutated proteins. The energy for the wild-type and mutated proteins is calculated by using molecular dynamics simulations along with simulated annealing. Our results show significant differences in energy between hotspot mutations and the wild type. Based on the findings, we investigate the correlation between molar masses of the target residue and the relative energy with respect to the wild type. Our results indicate that the relative energy changes play a pivotal role in bioactivity, in conformity with observations in the rate of mutation in biology.

Basic helix loop helix (bHLH) transcription factor 3 (TCF3, E2A) is regulated by androgens in prostate cancer cells

TCF3 (E2A) is a multifunctional basic helix loop helix (bHLH) transcription factor that is over-expressed in prostate cancer (PCa) as compared to normal prostate and that it acts as a tumor promoter in PCa. Given the diverse biological pathways regulated/influenced by TCF3, little is known about the mechanisms that regulate its expression. TCF3 expression in androgen sensitive LNCaP and insensitive C81 PCa cell lines was determined following treatments with androgen receptor (AR) agonist R1881 and antagonist Casodex. In silico analysis was used to discover putative Androgen Response Elements (ARE) in the TCF3 promoter/intron region. Chromatin Immunoprecipitation (ChIP) with AR antibody and luciferase reporter assays on the above mentioned cell lines was used to confirm AR biding and AR dependent transcriptional activity respectively. The results were confirmed by demonstrating TCF3 expression in LNCaP PCa xenograft models. The results suggested that TCF3 transcript increased in response to R1881 in LNCaP cells but was constitutively expressed in C-81 cell lines. The promoter/Intron region of the TCF3 gene was predicted to contain two putative ARE sites ARE1 and ARE2. ChIP after treatment of LNCaP and C81 cells with R1881 and Casodex showed that the ARE1 and ARE2 were bound by AR in LNCaP cells only in the presence of R1881, whereas C81 cells showed constitutive AR binding. Similar results were observed in luciferase reporter assays indicating that TCF3 is activated by AR in LNCaP cell lines whereas it is independent of androgens in C81 cell line. Luciferase reporter assays also confirmed that ARE1 alone drives androgen dependent transcription. TCF3 expression was only observed in castration resistant LNCaP xenografts in castrated mice. In conclusion, we demonstrate that in PCa androgen receptor regulates the expression of TCF3 which is mediated in part via a consensus androgen response element. The shift in TCF3 expression from androgen regulated to androgen independent during prostate cancer progression, together with lack of expression in normal prostate may provide mechanistic basis underlying the transition of androgen receptor from a tumor suppressor to an oncogene in prostate cancer.

NRG1 and KITL Signal Downstream of Retinoic Acid in the Germline to Support Soma-Free Syncytial Growth of Differentiating Spermatogonia

Defined culture systems supporting spermatogonial differentiation will provide experimental platforms to study spermatogenesis. However, germline-intrinsic signaling mechanisms sufficient to support spermatogonial differentiation without somatic cells remain largely undefined. Here, we analyzed EGF superfamily receptor and ligand diversity in rat testis cells, and delineated germline-intrinsic signaling via an ERBB3 co-transducer, ERBB2, as essential for retinoic acid-induced syncytial growth by differentiating spermatogonia. Like the ERBB2/3 agonist NRG1, we found KIT Ligand (KITL) robustly supported spermatogonial differentiation without serum or somatic cells. ERBB2 inhibitors failed to disrupt KITL-dependent spermatogonial development, and, KITL prevented ERBB3-deficient spermatogonial degeneration upon differentiation. Thus, we report NRG1 and KITL activate alternative pathways downstream of retinoic acid signaling in the germline that are essential for stem cells to undergo pre-meiotic steps of spermatogenesis in culture. Robust serum/soma-free spermatogonial differentiation opens new doors to study mammalian germ cell biology in culture, which will facilitate the discovery of spermatogenic factors that can drive meiotic progression in vitro.

Abstract 1235: Inducible overexpression of bHLH transcriptional regulator Id4 abrogates tumorigenicity of prostate cancer xenografts

Introduction: Inhibitor of DNA binding/differentiation 4 (Id4) has been shown to be highly expressed during prostate development. However, in many cancers including prostate, Id4 is epigenetically silenced due to promoter hyper-methylation. In this study we developed a doxycycline inducible system for Id4 overexpression and show that controlled increase of Id4 in an aggressive metastatic prostate cancer cell line DU145, which lacks Id4 expression results in attenuation of tumor forming ability of this cell line and confirming its role as a tumor suppressor.

Methods: Tetracycline inducible system was used to stably overexpress Id4 in DU145 cells. Empty vector backbone was used as a control. The Id4 overexpressed (DU(+)iId4) and vector control (DU(+)iVC) cells were used to investigate migration (scratch wound assay) and anchorage independent growth (soft agar assay). Tumorigenicity of DU(+)iId4 and DU(+)iVC cells was investigated in Scid beige mice. The gene expression profile between DU(+)iId4 and DU(+)iVC cells was analyzed by RNAseq. The DU(+)iId4 and DU(+)iVC tumors from mice were used for immunohistochemistry to validate prostate cancer pathways and RNAseq data.

Results: Id4 was cloned in pcDNA4/TO/myc-His version A and stably transfected and clonally selected for overexpression in DU145 cells stably expressing pcDNA6/TR. The overexpression of Id4 on induction by doxycycline (a tetracycline analogue) was confirmed by qRT-PCR and western blotting. A clone with maximum expression was selected for further studies. On inducing the DU145 cells with doxycycline, an increase in apoptosis was observed as compared to un-induced DU145 as well as cells expressing the empty control vector. Decrease in migration and anchorage independent colony forming ability was also observed upon induction of Id4 in scratch wound and soft agar assay, respectively. Subcutaneous injection of DU145 cells in Scid beige mice resulted in formation of tumors, however upon induction of Id4 expression by doxycycline from day 0 or 2 weeks after injection of the cells showed a significant decrease in the tumor forming ability of the DU145 cells as evident from the reduction in the tumor weight and volume. Immunohistochemistry on tumor tissues was found to be in support of the RNAseq data.

Conclusion: This study reports for the first time that conditional overexpression of tumor suppressor Id4 in prostate cancer cell lines DU145 results in diminution of tumor formation. The data describes use of a system that allows for the temporal regulation of Id4 expression in vivo which could act as a preliminary step in mimicking controlled delivery of Id4 for therapeutic purpose.

Acknowledgement: This study was supported by NIH/NCI RO1 CA128914 and NIH/NCRR/RCMI G12MD007590.

Citation Format: Divya Patel, Derrick J. Morton, Maxwell Korang-Yeboah, Yamini Gorantla, Sushma Bhosle, Perri Nagappan, Nathen Bowen, Jaideep Chaudhary. Inducible overexpression of bHLH transcriptional regulator Id4 abrogates tumorigenicity of prostate cancer xenografts. [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 1235. doi:10.1158/1538-7445.AM2015-1235

Polycaprolactone/maltodextrin nanocarrier for intracellular drug delivery: formulation, uptake mechanism, internalization kinetics, and subcellular localization

Prostate cancer (PCa) disease progression is associated with significant changes in intracellular and extracellular proteins, intracellular signaling mechanism, and cancer cell phenotype. These changes may have direct impact on the cellular interactions with nanocarriers; hence, there is the need for a much-detailed understanding, as nanocarrier cellular internalization and intracellular sorting mechanism correlate directly with bioavailability and clinical efficacy. In this study, we report the differences in the rate and mechanism of cellular internalization of a biocompatible polycaprolactone (PCL)/maltodextrin (MD) nanocarrier system for intracellular drug delivery in LNCaP, PC3, and DU145 PCa cell lines. PCL/MD nanocarriers were designed and characterized. PCL/MD nanocarriers significantly increased the intracellular concentration of coumarin-6 and fluorescein isothiocyanate-labeled bovine serum albumin, a model hydrophobic and large molecule, respectively. Fluorescence microscopy and flow cytometry analysis revealed rapid internalization of the nanocarrier. The extent of nanocarrier cellular internalization correlated directly with cell line aggressiveness. PCL/MD internalization was highest in PC3 followed by DU145 and LNCaP, respectively. Uptake in all PCa cell lines was metabolically dependent. Extraction of endogenous cholesterol by methyl-β-cyclodextrin reduced uptake by 75%±4.53% in PC3, 64%±6.01% in LNCaP, and 50%±4.50% in DU145, indicating the involvement of endogenous cholesterol in cellular internalization. Internalization of the nanocarrier in LNCaP was mediated mainly by macropinocytosis and clathrin-independent pathways, while internalization in PC3 and DU145 involved clathrin-mediated endocytosis, clathrin-independent pathways, and macropinocytosis. Fluorescence microscopy showed a very diffused and non-compartmentalized subcellular localization of the PCL/MD nanocarriers with possible intranuclear localization and minor colocalization in the lysosomes with time.

Inhibitor of differentiation 4 (ID4) acts as an inhibitor of ID-1, -2 and -3 and promotes basic helix loop helix (bHLH) E47 DNA binding and transcriptional activity

The four known ID proteins (ID1-4, Inhibitor of Differentiation) share a homologous helix loop helix (HLH) domain and act as dominant negative regulators of basic-HLH transcription factors. ID proteins also interact with many non-bHLH proteins in complex networks. The expression of ID proteins is increasingly observed in many cancers. Whereas ID-1, ID-2 and ID-3, are generally considered as tumor promoters, ID4 on the contrary has emerged as a tumor suppressor. In this study we demonstrate that ID4 heterodimerizes with ID-1, -2 and -3 and promote bHLH DNA binding, essentially acting as an inhibitor of inhibitors of differentiation proteins. Interaction of ID4 was observed with ID1, ID2 and ID3 that was dependent on intact HLH domain of ID4. Interaction with bHLH protein E47 required almost 3 fold higher concentration of ID4 as compared to ID1. Furthermore, inhibition of E47 DNA binding by ID1 was restored by ID4 in an EMSA binding assay. ID4 and ID1 were also colocalized in prostate cancer cell line LNCaP. The alpha helix forming alanine stretch N-terminal, unique to HLH ID4 domain was required for optimum interaction. Ectopic expression of ID4 in DU145 prostate cancer line promoted E47 dependent expression of CDKNI p21. Thus counteracting the biological activities of ID-1, -2 and -3 by forming inactive heterodimers appears to be a novel mechanism of action of ID4. These results could have far reaching consequences in developing strategies to target ID proteins for cancer therapy and understanding biologically relevant ID-interactions.

Targeted Germline Modifications in Rats Using CRISPR/Cas9 and Spermatogonial Stem Cells

Organisms with targeted genomic modifications are efficiently produced by gene editing in embryos using CRISPR/Cas9 RNA-guided DNA endonuclease. Here, to facilitate germline editing in rats, we used CRISPR/Cas9 to catalyze targeted genomic mutations in rat spermatogonial stem cell cultures. CRISPR/Cas9-modified spermatogonia regenerated spermatogenesis and displayed long-term sperm-forming potential following transplantation into rat testes. Targeted germline mutations in Epsti1 and Erbb3 were vertically transmitted from recipients to exclusively generate "pure," non-mosaic mutant progeny. Epsti1 mutant rats were produced with or without genetic selection of donor spermatogonia. Monoclonal enrichment of Erbb3 null germlines unmasked recessive spermatogenesis defects in culture that were buffered in recipients, yielding mutant progeny isogenic at targeted alleles. Thus, spermatogonial gene editing with CRISPR/Cas9 provided a platform for generating targeted germline mutations in rats and for studying spermatogenesis.

Interferon inducible antiviral MxA is inversely associated with prostate cancer and regulates cell cycle, invasion and Docetaxel induced apoptosis

BACKGROUND

The interferon inducible Myxovirus (influenza virus) resistance A (MxA) is considered as a key mediator of the interferon-induced antiviral response. Mx proteins contain the typical GTP-binding motif and show significant homology to dynamin family of GTPases. Strong interaction of MxA with tubulin suggests that Mx proteins could be involved in mitosis. Studies have shown that MxA inhibit tumor motility/metastasis and virus induced apoptosis. However, the clear association between MxA expression and cancer remains unknown. Meta-analysis suggested that MxA expression was inversely correlated with prostate cancer (PCa). In this study, we demonstrate the expression MxA in PCa and its functional significance on the cancer phenotype.

METHODS

The expression of MxA protein in prostate cancer was examined by immuno-histochemistry. MxA was knocked down (shMxA) or over-expressed (pMxA) in DU145 or LNCaP PCa cell lines respectively. These cell lines were used to study proliferation, apoptosis, invasion, migration, and anchorage independent growth. Co-localization of MxA with tubulin was performed by immuno-cytochemistry following Docetaxel treatment.

RESULTS

The expression of MxA protein was significantly decreased in PCa as compared to the normal tissues. DU145 cells lacking MxA (DU145 + chMxA) showed significant increase in proliferation, associated with decreased expression of CDKN1A and B. Increased migration, anchorage independent growth in DU145 + shMxA cells was associated with increased MMP13 expression. Tubulin organization was also dependent on MxA expression. Tubulin polymerizing agents such as Docetaxel was less effective in promoting apoptosis in cells lacking MxA due to altered tubulin organization. Gain of MxA expression in LNCaP cells (LNCaP + pMxA) resulted in cell cycle arrest that was associated with increased expression of CDKN1A. MxA expression was also down-regulated by dihydrotestosterone in LNCaP cells.

CONCLUSIONS

MxA expression is inversely correlated with prostate cancer. Down-regulation of MxA in LNCaP cells by DHT suggests that MxA could play a significant role in disease progression. Loss of MxA expression results in increased metastasis and decreased sensitivity to Docetaxel suggesting that MxA expression could determine the outcome of chemo-therapeutic treatment. Additional studies will be required to fully establish the cross-talk between androgen receptor-IFN pathway in regulating MxA expression in the normal prostate and prostate cancer. Prostate 75:266-279, 2015. © 2014 Wiley Periodicals, Inc.

Prostate cancer epigenome

Prostate cancer is a major health burden within the ever-increasingly aging US population. The molecular mechanisms involved in prostate cancer are diverse and heterogeneous. In this context, epigenetic changes, both global and gene specific, are now an emerging alternate mechanism in disease initiation and progression. The three major risk factors in prostate cancer: age, geographic ancestry, and environment are all influenced by epigenetics and additional significant insight is required to gain an understanding of the underlying mechanisms. The androgen receptor and its downstream effector pathways, central to prostate cancer initiation and progression, are subject to a multitude of epigenetic alterations. In this review we focus on the global perspective of epigenetics and the use of recent next-generation sequencing platforms to interrogate epigenetic changes in the prostate cancer genome.

Inhibitor of differentiation 4 (ID4): From development to cancer

Highly conserved Inhibitors of DNA-Binding (ID1-ID4) genes encode multi-functional proteins whose transcriptional activity is based on dominant negative inhibition of basic helix-loop-helix (bHLH) transcription factors. Initial animal models indicated a degree of compensatory overlap between ID genes such that deletion of multiple ID genes was required to generate easily recognizable phenotypes. More recently, new model systems have revealed alterations in mice harboring deletions in single ID genes suggesting complex gene and tissue specific functions for members of the ID gene family. Because ID genes are highly expressed during development and their function is associated with a primitive, proliferative cellular phenotype there has been significant interest in understanding their potential roles in neoplasia. Indeed, numerous studies indicate an oncogenic function for ID1, ID2 and ID3. In contrast, the inhibitor of differentiation 4 (ID4) presents a paradigm shift in context of well-established role of ID1, ID2 and ID3 in development and cancer. Apart from some degree of functional redundancy such as HLH dependent interactions with bHLH protein E2A, many of the functions of ID4 are distinct from ID1, ID2 and ID3: ID4 proteins a) regulate distinct developmental processes and tissue expression in the adult, b) promote stem cell survival, differentiation and/or timing of differentiation, c) epigenetic inactivation/loss of expression in several advanced stage cancers and d) increased expression in some cancers such as those arising in the breast and ovary. Thus, in spite of sharing the conserved HLH domain, ID4 defies the established model of ID protein function and expression. The underlying molecular mechanism responsible for the unique role of ID4 as compared to other ID proteins still remains largely un-explored. This review will focus on the current understanding of ID4 in context of development and cancer.

Inhibitor of differentiation 4 (ID4) inactivation promotes de novo steroidogenesis and castration-resistant prostate cancer

Prostate cancer (PCa) is the most commonly diagnosed cancer in men in the Western world. The transition of androgen-dependent PCa to castration-resistant (CRPC) is a major clinical manifestation during disease progression and presents a therapeutic challenge. Our studies have shown that genetic ablation of inhibitor of differentiation 4 (Id4), a dominant-negative helix loop helix protein, in mice results in prostatic intraepithelial neoplasia lesions and decreased Nkx3.1 expression without the loss of androgen receptor (Ar) expression. ID4 is also epigenetically silenced in the majority of PCa. However, the clinical relevance and molecular pathways altered by ID4 inactivation in PCa are not known. This study investigates the effect of loss of ID4 in PCa cell lines on tumorigenicity and addresses the underlying mechanism. Stable silencing of ID4 in LNCaP cells (L-ID4) resulted in increased proliferation, migration, invasion, and anchorage-independent growth. An increase in the rate of tumor growth, weight, and volume was observed in L-ID4 xenografts compared with that in the LNCaP cells transfected with nonspecific short hairpin RNA (L+ns) in noncastrated mice. Interestingly, tumors were also observed in castrated mice, suggesting that loss of ID4 promotes CRPC. RNA sequence analysis revealed a gene signature mimicking that of constitutively active AR in L-ID4, which was consistent with gain of de novo steroidogenesis. Prostate-specific antigen expression as a result of persistent AR activation was observed in L-ID4 cells but not in L+ns cells. The results demonstrate that ID4 acts as a tumor suppressor in PCa, and its loss, frequently observed in PCa, promotes CRPC through constitutive AR activation.

A-single spermatogonia heterogeneity and cell cycles synchronize with rat seminiferous epithelium stages VIII-IX

In mammalian testes, "A-single" spermatogonia function as stem cells that sustain sperm production for fertilizing eggs. Yet, it is not understood how cellular niches regulate the developmental fate of A-single spermatogonia. Here, immunolabeling studies in rat testes define a novel population of ERBB3(+) germ cells as approximately 5% of total SNAP91(+) A-single spermatogonia along a spermatogenic wave. As a function of time, ERBB3(+) A-single spermatogonia are detected during a 1- to 2-day period each 12.9-day sperm cycle, representing 35%-40% of SNAP91(+) A-single spermatogonia in stages VIII-IX of the seminiferous epithelium. Local concentrations of ERBB3(+) A-single spermatogonia are maintained under the mean density measured for neighboring SNAP91(+) A-single spermatogonia, potentially indicative of niche saturation. ERBB3(+) spermatogonia also synchronize their cell cycles with epithelium stages VIII-IX, where they form physical associations with preleptotene spermatocytes transiting the blood-testis barrier and Sertoli cells undergoing sperm release. Thus, A-single spermatogonia heterogeneity within this short-lived and reoccurring microenvironment invokes novel theories on how cellular niches integrate with testicular physiology to orchestrate sperm development in mammals.

-174G/C polymorphism in the interleukin-6 promoter is differently associated with prostate cancer incidence depending on race

Interleukin-6 (IL-6), a pro-inflammatory cytokine, is involved in prostate cancer progression, including androgen independence. Serum IL-6 levels also correlate with prostate tumor burden, prostate-specific antigen levels and metastasis. Since circulating cytokine levels vary considerably inter-individually, such variation could be linked to genetic factors, including genetic polymorphism. The -174G>C/rs1800795 polymorphism in the IL-6 promoter is functionally relevant in terms of transcriptional regulation and disease association. We investigated a possible association of the -174G/C polymorphism with prostate cancer. Since significant racial disparities exist in prostate cancer incidence, we also investigated this association between the -174G/C polymorphism and prostate cancer in Caucasians and African-Americans, separately. Direct sequencing of the PCR amplicon from genomic DNA was used for genotyping rs1800795 in all subjects [age-matched controls (N = 140) and prostate cancer patients (N = 164)]. Sample size and power was calculated using the PGA software. We found the GG genotype to be associated with increased risk of prostate cancer in Caucasian subjects, whereas the CC genotype was associated with increased risk in the African-American sample set. Such a dimorphic genotypic association with cancer and race is unique and suggests a complex gene-gene and gene-environment interaction.

Id4 promotes senescence and sensitivity to doxorubicin-induced apoptosis in DU145 prostate cancer cells

Inhibitor of differentiation proteins (Id1, 2, 3 and 4) are dominant negative regulators of basic helix loop helix transcription factors and play dominant roles in cancer cells, spanning several molecular pathways including senescence, invasion, metastasis, proliferation and apoptosis. In contrast to high Id1, Id2 and Id3 expression, the expression of Id4 is epigenetically silenced in prostate cancer. In the present study we demonstrated a novel role of Id4, that of promotion of cellular senescence in prostate cancer cells.

MATERIALS AND METHODS

Id4 was ectopically expressed in DU145 cells (DU145+Id4). The cells treated with Doxorubicin (0-500 nm) or vehicle control were analyzed for apoptosis, senescence (SA-beta Galactosidase), and expression of CDKN1A (p21), CDKN1B(p27), CDKN2A (p16), E2F1, vimentin and E-cadherin by immuno-histochemistry and/or Western blot.

RESULTS

In the present study we demonstrated that Id4 promotes cellular senescence in prostate cancer cell line DU145. Ectopic overexpression of Id4 in androgen receptor-negative DU145 prostate cancer cells resulted in increased expression of p16, p21, p27, E-cadherin and vimentin but down-regulated E2F1 expression. Id4 also potentiated the effect of doxorubicin induced senescence and apoptosis.

CONCLUSION

The absence of functional p16, pRB and p53 in DU145 suggests that Id4 could alter additional molecular pathways such as those involving E2F1 to promote senescence and increased sensitivity to doxorubicin-induced apoptosis. The results of the present study support the role of Id4 as a tumor suppressor in prostate cancer.

Supramolecular Assembly of DNA on Graphene Nanoribbons

Graphene's adhesive and charge delocalization properties offer the opportunity for the direct study of biological molecule in the nanoscale regime. The inherent charge on DNA base pairs and the associated phosphate backbone can be probed by non-covalent interactions with graphene, which is a useful platform for the creation of anisotropic nanopatterned biological assemblies. Here, we report the graphene nanoribbon (GNR) supported anisotropic supramolecular self-assembly of single stranded adenine (A), cytosine (C), guanine (G), thymine (T), AT, and GC 20mer oligonucleotides, as well as the unique ordering of double stranded plasmid (circular) and Herring sperm (linear) DNA. The GNRs serve as a double sided adhesive platform for attachment to the SiO2 substrate, as well as DNA oligomers and polymers. The self-assembly is attributed to donor-acceptor interactions between DNA and graphene. These findings demonstrate that the DNA-GNR assembly yields a prospective route to novel bio-relevant nanostructures.

Linking spermatid ribonucleic acid (RNA) binding protein and retrogene diversity to reproductive success

Spermiogenesis is a postmeiotic process that drives development of round spermatids into fully elongated spermatozoa. Spermatid elongation is largely controlled post-transcriptionally after global silencing of mRNA synthesis from the haploid genome. Here, rats that differentially express EGFP from a lentiviral transgene during early and late steps of spermiogenesis were used to flow sort fractions of round and elongating spermatids. Mass-spectral analysis of 2D gel protein spots enriched >3-fold in each fraction revealed a heterogeneous RNA binding proteome (hnRNPA2/b1, hnRNPA3, hnRPDL, hnRNPK, hnRNPL, hnRNPM, PABPC1, PABPC4, PCBP1, PCBP3, PTBP2, PSIP1, RGSL1, RUVBL2, SARNP2, TDRD6, TDRD7) abundantly expressed in round spermatids prior to their elongation. Notably, each protein within this ontology cluster regulates alternative splicing, sub-cellular transport, degradation and/or translational repression of mRNAs. In contrast, elongating spermatid fractions were enriched with glycolytic enzymes, redox enzymes and protein synthesis factors. Retrogene-encoded proteins were over-represented among the most abundant elongating spermatid factors identified. Consistent with these biochemical activities, plus corresponding histological profiles, the identified RNA processing factors are predicted to collectively drive post-transcriptional expression of an alternative exome that fuels finishing steps of sperm maturation and fitness.

Id4 deficiency attenuates prostate development and promotes PIN-like lesions by regulating androgen receptor activity and expression of NKX3.1 and PTEN

Background

Inhibitor of differentiation 4 (Id4), a member of the helix-loop-helix family of transcriptional regulators has emerged as a tumor suppressor in prostate cancer. Id4 is expressed in the normal prostate where its expression is also regulated by androgens. In this study we investigated the effect of loss of Id4 (Id4-/-) on adult prostate morphology.

Methods

Histological analysis was performed on prostates from 6-8 weeks old Id4-/-, Id4+/- and Id4+/+ mice. Expression of Id1, Sox9, Myc, androgen receptor, Akt, p-Akt, Pten and Nkx3.1 was investigated by immunohistochemistry. Androgen receptor binding on NKX3.1 promoter was studied by chromatin immuno-precipitation. Id4 was either over-expressed or silenced in prostate cancer cell lines DU145 and LNCaP respectively followed by analysis of PTEN, NKX3.1 and Sox9 expression.

Results

Id4-/- mice had smaller prostates with fewer tubules, smaller tubule diameters and subtle mPIN like lesions. Levels of androgen receptor were similar between wild type and Id4-/- prostate. Decreased NKX3.1 expression was in part due to decreased androgen receptor binding on NKX3.1 promoter in Id4-/- mice. The increase in the expression of Myc, Sox9, Id1, Ki67 and decrease in the expression of PTEN, Akt and phospho-AKT was associated with subtle mPIN like lesions in Id4-/- prostates. Finally, prostate cancer cell line models in which Id4 was either silenced or over-expressed confirmed that Id4 regulates NKX3.1, Sox9 and PTEN.

Conclusions

Our results suggest that loss of Id4 attenuates normal prostate development and promotes hyperplasia/dysplasia with subtle mPIN like lesions characterized by gain of Myc and Id1 and loss of Nkx3.1 and Pten expression. One of the mechanisms by which Id4 may regulate normal prostate development is through regulating androgen receptor binding to respective response elements such as those on NKX3.1 promoter. In spite of these complex alterations, large neoplastic lesions in Id4-/- prostates were not observed suggesting the possibility of mechanisms/pathways such as loss of Akt that could restrain the formation of significant pre-cancerous lesions.

Inhibitor of differentiation 1 (Id1) and Id3 proteins play different roles in TGFβ effects on cell proliferation and migration in prostate cancer cells

BACKGROUND

In prostate cancer cells, transforming growth factor β (TGFβ) inhibits proliferation in earlier stages of the disease; however, the cancer cells become refractory to growth inhibitory effects in advanced stages where TGFβ promotes cancer progression and metastasis. Inhibitor of differentiation (Id) family of closely related proteins (Id1-Id4) are dominant negative regulators and basic helix loop helix (bHLH) transcription factors and in general promote proliferation, and inhibit differentiation. In the present study, we have investigated the role of Id1 and Id3 proteins in the growth inhibitory effects of TGFβ on prostate cancer cells.

METHODS

The effect of TGF β on proliferation and Id1 and Id3 expression were investigated in PZ-HPV7, DU145, and PC3 cells. Id1 silencing through siRNA was also used in DU145 and PC3 cells to examine its role in anti-proliferative and migratory effects of TGFβ.

RESULTS

TGFβ increased expression of Id1 and Id3 in all cell lines followed by a later down regulation of Id1 in PZ-HPV7 expression and DU145 cells but not in PC3 cells. Id3 expression remained elevated in all three cell lines. This loss of Id1 protein correlated with an increase of CDKNI p21. Id1 knockdown in both DU145 and PC3 cells resulted in decreased proliferation. However, while TGFβ caused a further decrease in proliferation of DU145, but had no further effects in PC3 cells. Knockdown of Id1 or Id3 inhibited TGFβ1induced migration in PC3 cells.

CONCLUSIONS

These findings suggest an essential role of Id1 and Id3 in TGFβ1 effects on proliferation and migration in prostate cancer cells.

Abstract 758: Studies in cancer models with AGX51, a Direct Transcriptional RegulatorTM

Studies in cancer models with AGX51, a Direct Transcriptional RegulatorTM

The inhibitors of differentiation (Id) proteins (Id1, Id2, Id3, and Id4) are negative regulators of differentiation that act by sequestering basic helix loop helix (bHLH, e.g. E47) transcription factors. Ids are highly expressed during embryonic development but in adult tissues their expression is rare to absent. However, Id proteins are required for tumor angiogenesis, highly expressed in many cancers and as shown in many clinical studies, associated with an aggressive phenotype and a poor clinical outcome As a proof of concept, decreased angiogenesis and tumor load as a result of blocking Id expression by antisense and siRNA molecules demonstrated that Id is a compelling anti-cancer target. Despite these findings, the Ids are a heretofore unexplored target for the treatment of cancer. While no anti-Id agent has been studied clinically or has undergone preclinical development, AGX recently discovered and patented the first unique and potent anti-Id agent, AGX51. This small molecule is an inhibitor of the Id1-E47 interaction and was discovered through a systematic research effort using x-ray crystallography, gel shift (EMSA) assays, Matrigel evaluations and xenograft studies. AGX51 is the founding member of a new class of therapeutics: Direct Transcriptional RegulatorsTM.

In preclinical studies: (1) At a dose below 7 mg/kg, bid, AGX51 significantly blocked the growth of tumors in mice with implanted human breast cancer cells when treated briefly with a taxane like Taxol®, paclitaxel, or Taxotere®, docetaxel. This effect of AGX51 was expected based on the discovery that endothelial cell production in the bone marrow is responsible for the rapid repair to damaged vasculature after administration of paclitaxel or vascular disrupters such as ZD6126 or AVE8062, through mobilization of endothelial precursor cells (EPCs) followed by homing of the EPCs to the damaged vasculature; (2) At a dose below 20 nM, AGX51 restored cell cycle control in DU-145 human prostate cancer cells; (3) At low micromolar concentrations, AGX51 blocked migration of DU-145 cancer cells in “scratch” assays; (4) As a single agent, AGX51 completely blocked tumor associated angiogenesis in nude mice implanted with MDA-MB231 human breast cancer cells at a dose of 60 mg/kg, bid; (5) As expected, AGX51 restored levels of p21 and p27, two important mediators of cell cycle regulation in both PC3 and DU145 cancer cells; (6) AGX51 caused no toxicity in multiple day dosing based on weight, clinical chemistry or hematology measurements; (7) AGX51 has a terminal elimination half-life in mice of approximately 6 hours, which is suggestive of ultimate bid and perhaps even qd dosing in man. In summary, a specific inhibitor of Id-E47 interaction that has anti-tumor activity is described for the first time. This research was supported by AngioGenex, Inc.

Citation Format: William Garland, Richard Salvador, Jaideep Chaudhary. Studies in cancer models with AGX51, a Direct Transcriptional RegulatorTM. [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 758. doi:10.1158/1538-7445.AM2013-758

Abstract 5455: Differential regulation of E2A (TCF3) by androgens in prostate cancer cells

Introduction: E2A (TCF3) is a multifunctional basic helix loop helix (bHLH) transcription factor. E2A promotes cell differentiation, acts as a negative regulator of cell proliferation in normal cells and cancer cell lines and is required for normal B-cell development. Previous studies from our laboratory has shown that E2A expression is highly increased in prostate cancer as compared to normal prostate and that it acts as a tumor promoter in prostate cancer. Given the diverse biological pathways regulated/ influenced by E2A little is known about its regulation in prostate cancer.

Experimental design: E2A expression in androgen sensitive LNCaP and insensitive C81 prostate cancer cell lines was determined by western blot after treatments with androgen receptor (AR) agonist R1881 and antagonist casodex. Putative Androgen Response Elements (ARE) were identified in the first intronic region of the E2A gene using some of the online bioinformatics tools and confirmed by Chromatin Immunoprecipitation (ChIP) with AR antibody and Luciferase reporter assays on the above mentioned cell lines after treatments with R1881 and casodex.

Results: E2A expression was found to increase with the increasing aggrasiveness of prostate cancer cell lines as compared to normal prostate epithelial cell line RWPE1. When androgen responsive cell line LNCaP was treated with R1881 there was an increased expression of E2A which decreased upon treatment with antiandrogen casodex whereas the E2A expression remained unaltered upon similar treatments in androgen insensitive cell line C81. The first intronic region of the E2A gene was predicted to contain two putative ARE sites. ChIP after treatment of LNCaP and C81 cells with R1881 and casodex showed that the intronic region was bound by AR in LNCaP cells only in the presence of R1881, whereas C81 cells showed a pulldown with AR in presence as well as absence of R1881. Similar results were observed in luciferase reporter assays indicating that E2A is transactivated by AR in LNCaP cell lines whereas it is independent of androgens in C81 cell line. Furthermore, Luciferase reporter assays also confirmed that only one of the two predicted putative AREs was functionally active and responsible for the androgen mediated regulation of E2A.

Conclusion: Our results indicate that E2A is differentially regulated in Prostate cancer cell lines. The increased expression of E2A and its role as a tumor promoter in prostate cancer cell lines may be contributed to its loss of androgen dependence as is evident in its progression from androgen dependent LNCaP to independent C81 cells.

Acknowledgements: This study was supported by NIH/NCI RO1 CA128914 and NIH/NCRR/RCMI G12RR03062.

Citation Format: Divya Patel, Jaideep Chaudhary. Differential regulation of E2A (TCF3) by androgens in prostate cancer cells. [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 5455. doi:10.1158/1538-7445.AM2013-5455

Abstract 4518: PCL/Maltodextrin delivered ID4 maintains its tumor suppressor role

INTRODUCTION: The Inhibitor of differentiation protein (Id) family has generated much attention in cancer cell biology due to its multifaceted role. These proteins have a helix–loop– helix (HLH) domain required for association with transcriptional factors but lack the basic amino acids required for DNA-binding therefore act as dominant-negative regulators of transcription. Tumor suppressor roles have been strongly associated with Id4 one of the four different isoforms identified so far. A recent study by Chaudhary et al indicated that Id4 was a potential tumor suppressor of prostate cancer with ectopic expression of Id4 in DU145 leading to increased apoptosis and decreased cell proliferation due in part by an S-phase arrest. Methylation mediated silencing of the Id4 gene has been associated with development of prostate cancer. In this study we evaluated the pro-apoptotic potential of intracellularly delivered Id4 using PCL/Maltodextrin nanoparticles as the delivery vector.

METHOD: PCL/Maltodextrin nanoparticles were formulated using the double emulsion solvent evaporation technique with a Nano Debee high-pressure homogenizer. Nanoparticles were lyophilized and characterized for their size, zeta potential, and encapsulation efficiency. Western blot analysis was conducted on Id4 loaded nanoparticles and nanoparticle treated DU 145 cell lines to confirm the presence and delivery of intact protein. Immuno-cytochemical analysis of Id4 expression was conducted on DU-145, LNCaP and LNCaP cells silenced with Id4 (LNCaP-Id4) pre and post treatment with Id4 loaded nanoparticles.The effect of nanoparticle delivered Id4 on cellular processes such as apoptosis, proliferation and transwell migration was also determined.

RESULTS: Id4 loaded PCL/Maltodextrin nanoparticles was successfully formulated with an average particle size of about 200nm. The formulation had encapsulation efficiency of 78.83±7.40% and percentage yield over 98%. Western blot analysis reveals that intact Id4 protein was successfully loaded and delivered to the cells. Immuno-cytochemical analysis of the three cell lines showed an efficient intracellular delivery of Id4 using PL/Maltodextrin with the intracellular amount increasing with time. The ICC analysis also showed possible intra- nuclear localization of Id4. Intracellular delivered Id4 increased the levels of Caspase 3/9 by about three folds associated with decreased mitochondrial membrane potential and plasma membrane asymmetry. The transwell migration assay also showed a significant decrease in cell migration after treatment with Id4 loaded nanoparticles in comparison to the untreated and blank nanoparticle group.

CONCLUSION: PCL/Maltodextrin nanocarrier can successfully deliver Id4 to the cytoplasm as well as nucleus of LNCaP-Id4, DU145 and LNCaP. Intracellular delivered Id4 maintains it pro apoptotic potential.

Citation Format: Maxwell Korang-Yeboah, Pankaj Sharma, Ashley Evans Knowell, Divya Patel, Yamini Gorantla, Swathi Chinaranagari, Ravi Palaniappa, Jaideep Chaudhary. PCL/Maltodextrin delivered ID4 maintains its tumor suppressor role. [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 4518. doi:10.1158/1538-7445.AM2013-4518

The myxovirus resistance A (MxA) gene -88G>T single nucleotide polymorphism is associated with prostate cancer

BACKGROUND

Myxovirus (influenza virus) resistance A (MxA) is an interferon stimulated antiviral protein that is required for a complete antiviral response. MxA polymorphism (rs2071430) is located within an Interferon Stimulated Response Element (ISRE) at position -88 in the gene's promoter region, and it has been associated with increased susceptibility to infections and various diseases. In general, the low promoter activity genotype (GG) promotes susceptibility, whereas the high promoter activity genotype (TT) confers protection to Hepatitis C viral infection. MxA's role in prostate cancer is not fully understood. Previous literature has shown that MxA may be a mediator of the effect of IFN on normal and tumor cell motility. MxA may act as a tumor suppressor and the level of expression may be a predictor of metastatic potential. Based on this information, in this study we investigated the association of this functional polymorphism (rs2071430) in MxA with prostate cancer.

METHODS

Sample size and power was calculated using the PGA software. Genomic DNA from a controls (n=140) and prostate cancer patients (n=164) were used for genotyping SNP rs2071430 on all samples. Statistical analysis was performed using logistic regression model.

RESULTS

A significant association was observed between rs2071430 genotype GG and prostate cancer. Individuals harboring the GG genotype are at an increased risk of prostate cancer. Data stratification reveals that the mutant GT genotype offers either offers some protection against prostate cancer in Caucasians.

CONCLUSIONS

MxA SNP rs2071430 GG genotype is significantly associated with prostate cancer irrespective of race. However, data stratification also suggests that the GT genotype is under-represented in Caucasian subjects suggesting its role in protection against prostate cancer in Caucasians. Although MxA is primarily implicated in viral infection, but it may be also be associated with prostate cancer. Recent studies have implicated viral and bacterial infections with increased prostate cancer risk. Expression of the high promoter activity genotype may offer resistance to prostate cancer infection and possibly influence clinical outcomes.

Id1 and Id3 expression is associated with increasing grade of prostate cancer: Id3 preferentially regulates CDKN1B

As transcriptional regulators of basic helix-oop-helix (bHLH) transcription and non-bHLH factors, the inhibitor of differentiation (Id1, Id2, Id3, and Id4) proteins play a critical role in coordinated regulation of cell growth, differentiation, tumorigenesis, and angiogenesis. Id1 regulates prostate cancer (PCa) cell proliferation, apoptosis, and androgen independence, but its clinical significance in PCa remains controversial. Moreover, there is lack of evidence on the expression of Id2 and Id3 in PCa progression. In this study we investigated the expression of Id2 and Id3 and reevaluated the expression of Id1 in PCa. We show that increased Id1 and Id3 protein expression is strongly associated with increasing grade of PCa. At the molecular level, we report that silencing either Id1 or Id3 attenuates cell cycle. Although structurally and mechanistically similar, our results show that both these proteins are noncompensatory at least in PCa progression. Moreover, through gene silencing approaches we show that Id1 and Id3 primarily attenuates CDKN1A (p21) and CDKN1B (p27), respectively. We also demonstrate that silencing Id3 alone significantly attenuates proliferation of PCa cells as compared with Id1. We propose that increased Id1 and Id3 expression attenuates all three cyclin-dependent kinase inhibitors (CDKN2B, -1A, and -1B) resulting in a more aggressive PCa phenotype.

Epigenetic inactivation of inhibitor of differentiation 4 (Id4) correlates with prostate cancer

The inhibitor of DNA-binding (Id) proteins, Id1–4 are negative regulators of basic helix-loop-helix (bHLH) transcription factors. As key regulators of cell cycle and differentiation, expression of Id proteins are increasingly observed in many cancers and associated with aggressiveness of the disease. Of all the four Id proteins, the expression of Id1, Id2, and to a lesser extent, Id3 in prostate cancer and the underlying molecular mechanism is relatively well known. On the contrary, our previous results demonstrated that Id4 acts as a potential tumor suppressor in prostate cancer. In the present study, we extend these observations and demonstrate that Id4 is down-regulated in prostate cancer due to promoter hypermethylation. We used prostate cancer tissue microarrays to investigate Id4 expression. Methylation specific PCR on bisulfite treated DNA was used to determine methylation status of Id4 promoter in laser capture micro-dissected normal, stroma and prostate cancer regions. High Id4 expression was observed in the normal prostate epithelial cells. In prostate cancer, a stage-dependent decrease in Id4 expression was observed with majority of high grade cancers showing no Id4 expression. Furthermore, Id4 expression progressively decreased in prostate cancer cell line LNCaP and with no expression in androgen-insensitive LNCaP-C81 cell line. Conversely, Id4 promoter hypermethylation increased in LNCaP-C81 cells suggesting epigenetic silencing. In prostate cancer samples, loss of Id4 expression was also associated with promoter hypermethylation. Our results demonstrate loss of Id4 expression in prostate cancer due to promoter hypermethylation. The data strongly support the role of Id4 as a tumor suppressor.

Abstract LB-282: Myxovirus (influenza virus) resistance 1 (MX1) polymorphism in prostate cancer

PURPOSE: Myxovirus (influenza virus) resistance 1 (MX1) is an interferon regulated gene responsible for a specific antiviral state against viral infection. We have previously shown that MX1 is up-regulated by androgens in the normal prostate epithelial cells; however, there is no known role for MX1 in cancer. Meta-analysis of different expression databases e.g. NCBI GEO and Oncomine suggested a strong inverse association between MX1 expression and prostate cancer. To confirm these studies, we performed Immunohistochemistry on normal prostate and prostate cancer tissues. Our data revealed that MX1 expression was indeed decreased in PCa as compared to normal, indicating that MX1 could be transcriptionally down-regulated. Literature studies indicated that MX1 down-regulation could be due to a specific polymorphism in the proximal MX1 promoter. In the promoter region of MX1 at position -88, a single nucleotide polymorphism G>T (rs2071430) is involved in modifying the gene expression. Interestingly, the rs2071430 harbors an interferon-stimulated response element (ISRE) that is required for MX1 expression in response to interferons. The “T” allele restores whereas the “G” allele attenuates ISRE binding resulting in increased or decreased MX1 expression respectively. Based on these observations we hypothesized that decreased expression of MX1 in prostate cancer could be due to the rs2071430 polymorphism. DESIGN METHODS: We investigated MX1 rs2071430 polymorphism in genomic DNA from equal number of disease free and prostate cancer samples (N=305). The sample size required to achieve statistically significant associations were calculated using the power calculator for case control genetic association studies. Polymorphism was detected by sequencing the PCR amplicon through SNPdetector to ensure that the SNP was due to heterozygous allelic variations and not due to sequencing artifacts. RESULTS: The data suggests that the GG genotype (low promoter activity) is higher in PCa (72%) as compared to normal (58.6%). The TT genotype (high activity) was higher in normal (5.7%) compared to PCa (2.4%). No TT genotype was observed in Caucasian normal samples. The results were statistically significant at P<0.05. Our results, for the first time demonstrate that MX1 is down-regulated in prostate cancer possibly at the transcriptional level due to ISRE polymorphism in the promoter region. ACKNOWLEDGEMENTS: This research is supported by NIH/NCMHD grant 1P20MD002285-01.

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 LB-282. doi:1538-7445.AM2012-LB-282

Abstract 63: Id4 acts as a tumor suppressor by inducing apoptosis and sensitizing prostate cancer cells to chemotherapeutic agent doxorubicin

PURPOSE:Id proteins (Id1, Id2, Id3, and Id4) function as dominant negative regulators of basic helix loop helix transcription factor family. They share the conserved HLH domain but lack the DNA binding basic domain. This domain configuration allows the Id proteins to dimerize with bHLH proteins. The Id-bHLH dimer therefore fails to bind the E box consensus sequence and activate transcription. In general Id1 and Id3 promote proliferation and inhibit differentiation and expression is generally high in many cancers. The function of Id4 appears to be unique as compared to Id1-Id3. Recent studies have demonstrated that Id4 is epigenetically silenced in many cancers including prostate cancer, suggesting that Id4 may in fact act as a tumor suppressor. The broad focus of this study is to investigate how Id4 acts as a tumor suppressor using prostate cancer cell line DU145, in which Id4 is epigenetically silenced. We report that at least two distinct mechanisms by which Id4 acts as a tumor suppressor is by inducing apoptosis and senescence in DU145 cells. Based on these observations, we hypothesize that Id4 will also sensitize prostate cancer cells to chemotherapeutic agents, such as doxorubicin. DESIGN METHODS: Apoptosis was quantitated using Annexin V staining in DU145 cells in which Id4 was ectopically expressed. We also used Mitocasp, which measures Caspase 3/7 activity and mitochondrial membrane potential for cytochrome c release. ηeta-galactosidase staining was used to confirm the senescent cells. Western blotting and other proteomics based approaches were used to determine the levels of apoptotic and senescence markers (Vimentin, Id1, MYC, MDM2, p16, and p21). Lastly, we treated prostate cancer cells with doxorubicin to investigate if Id4 promotes sensitivity to doxorubicin induced apoptosis. RESULTS Apoptosis assay indicated that over-expression of Id4 induced senescence and apoptosis in DU145 cells. At mRNA and protein levels, p21 and vimentin expression was increased. The expression of Id1, c-MYC, and MDM2 were decreased in DU145+Id4 cell line as compared to DU145. Our results also demonstrated that Id4 sensitizes DU145+Id4 cells to doxorubicin induced apoptosis that was Caspase 3/7 and cytochrome c dependent. CONCLUSIONS: Id4 may act as a tumor suppressor by inducing senescence and apoptosis in DU145 cells. Id4 not only induces apoptosis in prostate cancer cell line DU145, but also sensitizes these cells to doxorubicin. Id4 expression can thus be used as a clinical biomarker for prostate cancer progression and determining sensitivity to chemotherapeutic treatments. NIH/NCRR/RCMI grant #G12RR03062, NIH grant #R01CA128914

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 63. doi:1538-7445.AM2012-63

Abstract 3927: Loss of bHLH transcription factor Id4 modulates androgen receptor activity in prostate cancer progression

Inhibitor of differentiation 4 (Id4), a crucial developmental gene also expressed in the normal prostate, has been shown to act as a tumor suppressor in prostate cancer. Promoter hypermethylation of Id4 is observed in several advanced stage cancers including prostate cancer. The loss of Id4 expression correlates with androgen independent prostate cancer progression. Our studies suggest that Id4 plays a crucial role in mediating the transition from androgen dependent to androgen independent prostate cancer by mediating the AR axis potential and reprogramming several cellular mechanisms including migration, senescence and proliferation. Stable transfection of a full length Id4 plasmid into the androgen-independent prostate cancer cell line DU145 resulted in re-expression of AR and downstream AR response gene PSA. Id4 transfected cells also observed an androgen regulated rate of proliferation in responsive to treatment with AR antagonist, Casodex. AR antagonism also significantly reduced the rate of migration as observed by a scratch wound assay. Under closer observation, AR antagonist treatment with Casodex also inhibited translocation of AR to the nucleus of DU145 cells as observed by immunofluorescence. Previous studies in our laboratory have demonstrated that DU145+Id4 transfected cells undergo a significant level of senescence (∼ 32%) compared to normal DU145 cells (∼ 4%). Treatment of DU145+Id4 cells with the AR antagonist Casodex demonstrate that the rate of senescence in DU145+Id4 transfected cells is closely related to inhibition of AR activity. Our results suggest that Id4 may play a crucial role in the loss of AR activity in advanced stage prostate cancer progression. These results also suggest that the antagonism of AR nuclear translocation post Id4 induction closely regulates the rate of proliferation and the induction of a senescent phenotype. These results provide a significant correlation between Id4 expression and AR activity during prostate cancer progression. Loss of AR activity through Id4 promoter hypermethylation may play a crucial role in understanding castration resistant prostate cancer. Therefore, induction of Id4 may provide a novel therapeutic target for advanced stage prostate cancer treatment.

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 3927. doi:1538-7445.AM2012-3927

Abstract 1076: Ids act as downstream effectors in the transforming growth factor-β pathway in prostate cancer cells

Transforming growth factor-β (TGFβ) regulates proliferation, differentiation and differentiated function in a wide variety in cells. In prostate cancer cells, TGFβ inhibits proliferation in the earlier stages; however the cancer cells become refractory to growth inhibitory effects in advanced stages where TGFβ promotes cancer progression and metastasis. Intracellular mechanisms involved in these varied effects of TGFβ on prostate cancer cells are poorly understood. Inhibitor of Differentiation (Id) family of closely related proteins (Id1, Id2, Id3, Id4) inhibit binding of bHLH transcription factors to DNA and inhibit their effects on cell proliferation and differentiation. In the present study, we have investigated the involvement of Id1 and Id3 proteins in the effects of TGFβ on prostate cancer cells. Id1 and Id3 isoforms of protein are expressed in DU145 cells, which have previously been shown to be responsive to growth inhibitory effects of TGFβ. TGFβ caused a significant increase of protein levels of Id1 and Id3 as determined by Western blot analyses. This early induction was followed by a late downregulation of Id1, while Id3 induction remained stable. However in PC3 cells, this early induction of Id1 and Id3 proteins remained stable. Proliferation marker p21 was also induced in DU145 cells, while p21 protein was undetected in PC3 cells upon TGFβ1 treatment. Since previous studies have revealed that the loss of Id1 or Id3 is indicative of loss of proliferation in prostate cancer, Id1 effects were further studied between DU145 and PC3 cell lines. Id1 knockdown in DU145 cells resulted in enhanced inhibitory effects of TGFβ on cell proliferation. However, Id1 knockdown in PC3 did not influence TGFβ effects on proliferation. These results indicate that Id1 downregulation by TGFβ may be required for its effects on proliferation in DU145 cancer cells. We next investigated TGFβ effects on migration in PC3 cells, which TGFβ stimulation has been shown to increase its migration properties. Both Id1 and Id3 knockdown in PC3 cells decreased migratory response to TGFβ. This indicated that both Id1 and Id3 are necessary for TGFβ migratory properties of PC3 cells. Taken together, these results show that Id1 and Id3 act as necessary proteins in the TGFβ pathway on both proliferation and migration. Grant support: NIH 1P20MD002285-02 and RCMI G12RR03602

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 1076. doi:1538-7445.AM2012-1076

Abstract C57: The expression of 2′-5′ oligoadenylate synthetase in prostate cancer and its effect on prostate cancer cell cycle

2-5 oligoadenylate synthetase (OAS) is an IFN inducible enzyme that is part of innate immune response. During viral infections 2′-5′ OAS is activated by viral dsRNA or cellular RNA with significant double strand structure to synthesize 2-5 oligoadenylates (2-5A) from ATP; which in turn activates RNaseL, the latent ribonuclease. RNAseL degrades infectious RNA which imparts antiviral protection to the cell. OAS-RNaseL system also degrades cellular RNA and inhibits protein synthesis. The role of RNAseL as a tumor suppressor has been studied in prostate cancer cell lines and has been linked to hereditary prostate cancer (HPC). However HPC accounts for less than 9% of the overall prostate cancer incidence but the role of RNAseL in sporadic prostate cancer has not been established. Since OAS1 is the rate limiting enzyme in RNaseL activation, we therefore hypothesized that OAS could potentially act as tumor suppressor in the context of sporadic prostate cancer.

Methods: Immunohistochemistry was performed on human prostate cancer and normal prostate tissue to determine the expression of OAS1. RT-PCR and western blot was performed to detect the expression of OAS1 in LNCaP, DU145 and PC3 cell lines. Two alternative approaches were then used to investigate the effect of OAS1 on cell survival and its potential mechanism of action: OAS1 was over-expressed in LNCaP whereas it was silenced in DU145 cells. Cell cycle and apoptosis was quantitated by FACS analysis and the expression of key regulatory genes was determined by qRT-PCR and western blot analysis.

Results: Immunohistochemistry demonstrated that OAS1 expression is high in the normal prostate but decreased progressively with stage in prostate cancer. OAS1 was not expressed in LNCaP cells but its expression was high in DU145 and PC3 prostate cancer lines. Overexpression of OAS1 in LNCaP cells induced apoptosis and G1 arrest that was associated with increased p53, BAX and p21 expression. Alternatively, silencing of OAS in DU145 cells led to an increase in S phase and G2 cell population with a concomitant decrease in apoptosis.

Conclusion: Our prostate cancer cell line and prostate cancer tissue data strongly suggest that OAS1 is a candidate tumor suppressor that could be used as a potential biomarker for prostate cancer. Moreover, our previous study had shown a link between OAS1 polymorphism and prostate cancer incidence. Collectively data suggest the role of immune/inflammatory pathway in prostate cancer progression.

Citation Format: Sanjay Kumar Mandal, Jaideep Chaudhary. The expression of 2′-5′ oligoadenylate synthetase in prostate cancer and its effect on prostate cancer cell cycle [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr C57.

Abstract C5: Role of ID4 in the development of prostate in mouse

Introduction: The helix-loop-helix (HLH) family of transcriptional regulatory proteins are key players in a wide array of developmental processes. Studies in mice have convincingly demonstrated that HLH proteins are intimately involved in developmental events such as cellular differentiation and proliferation. The Id1, Id2, Id3 and Id4 gene products are closely related in their HLH regions and show similar affinities for the various E proteins but differ in their expression patterns. The function of Id proteins has recently been addressed by using a gene targeting approach in mice. Previous studies showed that Id1 null mutant mice do not exhibit abnormalities whereas reports from Id4−/− mice, found that Id4 is required for normal brain size, and regulates lateral expansion of the proliferative zone in the developing cortex and hippocampus. We have recently shown that Id4 is highly expressed in the normal human prostate, whereas its expression is epigenetically silenced in prostate cancer. However its role in normal prostate development and function is not known. Here, we demonstrate a role of Id4 in prostate development, by immunohistochemical techniques in Id4−/− mice.

Experimental procedures: To investigate the precise role of Id4 in cellular proliferation and development, normal H&E staining is performed on wild type and Id4−/− mouse prostate tissue. Expression of Id1, AR (Androgen receptor) and NKX3.1 on wild type and Id4−/− mouse prostate tissue was assessed by Immunohistochemistry.

Results: There was no change in expression of Id1 in wild type and Id4−/− mouse prostate. Androgen receptor and NKX3.1 expression in wild type mouse was mostly nuclear but there is no expression was observed in Id4−/− mouse prostate tissue. H&E staining of wild type and Id4−/− mouse prostate indicated a significant difference in the cellular morphology of Id4−/− mouse prostate tissue as compared to the wild type mouse prostate. In addition to cellular morphological changes, the size of androgen dependent reproductive tract organs such as seminal vesicle and prostate were significantly smaller in Id4−/− as compared to heterozygous and wild type mouse.

Conclusions: These results suggest a severe defect in androgen response pathway and support the role of Id4 in prostate development. Difference in the size of seminal vesicles and prostate in Id4−/− mouse shows the physiological role of Id4 in androgen target organs. Size difference could be due to lack of translocation of AR to nuclei however exact molecular mechanism remains to be investigated.

Acknowledgement: The research was supported by NIH/NCI-RO1CA128914 and in part by NIH/NCRR/RCMI G12RR03062.

Citation Format: Pankaj Sharma, Peri Nagappan, Mark A. Israel, Jaideep Chaudhary. Role of ID4 in the development of prostate in mouse [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr C5.

Abstract C55: The basic helix loop helix transcription factor E2A is associated with prostate cancer

Introduction: E2A (TCF3) is a multifunctional basic helix loop helix (bHLH), transcription factor. E2A regulates transcription of target genes by homo- or heterodimerization with other bHLH proteins such as MyoD, Mash, NeuroD and Id family of helix loop helix proteins. In general, E2A promotes cell differentiation, acts as a negative regulator of cell proliferation in normal cells and cancer cell lines and is required for normal B-cell development. Given the diverse biological pathways regulated/influenced by E2A little is known about its expression in cancer. Data mining approaches suggested that E2A is highly expressed in many cancers including prostate.

Experimental design: E2A protein expression was investigated in clinical prostate tumor samples on high density tissue microarray slides by Immunohistochemistry (IHC). The expression of E2A in PCA cell lines DU145 and PC3 was temporarily silenced using E2A siRNA (sc-35245, Santa Cruz Biotechnology) and its effect on the Proliferation, cell cycle, apoptosis, mitochondrial membrane potential and caspase 3/7 activation was determined. The underlying mechanism of action of E2A was investigated by analyzing the expression of potential E2A regulated genes involved in cell cycle.

Results: Consistent with increased E2A expression in prostate cancer suggested by meta-analysis, the E2A immunohistochemistry performed on prostate tissue microarrays demonstrated increased E2A expression in prostate cancer as compared to normal prostate. Silencing of E2A in prostate cancer cells DU145 and PC3 led to a significant reduction in proliferation due to G1 arrest that was in part mediated by increased CDKN1A(p21) and decreased Id1, Id3 and c-myc. E2A silencing in prostate cancer cell lines also resulted in increased apoptosis due to decrease in mitochondrial membrane permeability and increase in caspase 3/7 activity.

Conclusion: Based on our results, we propose that E2A could be an upstream regulator of Id1 and c-Myc which are highly expressed in prostate cancer. These results for the first time demonstrate that E2A could in fact acts as a tumor promoter at least in prostate cancer.

Acknowledgements: This study was supported by NIH/NCI RO1 CA128914 and NIH/NCRR/RCMI G12RR03062.

Citation Format: Divya Patel, Jaideep Chaudhary. The basic helix loop helix transcription factor E2A is associated with prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr C55.

2'-5' oligoadenylate synthetase 1 polymorphism is associated with prostate cancer

BACKGROUND

The antiviral, proapoptotic, antiproliferative gene 2'-5' oligoadenylate synthetase (2-5OAS1) converts adenosine triphosphate into a series of 2'-5' oligoadenylates (2-5A). In turn, 2-5A activates latent ribonuclease (RNaseL), a candidate hereditary prostate cancer gene. OAS1 polymorphism (reference single nucleotide polymorphism [SNP] 2660 [rs2660]) has been associated with increased susceptibility to infections and various diseases. In general, the low-enzyme-activity adenine-adenine (AA) genotype promotes susceptibility, whereas the high-enzyme-activity guanosine-guanosine (GG) genotype confers protection. In this study, the authors investigated the association of this functional OAS1 polymorphism (rs2660) with prostate cancer.

METHODS

Sample size and power were calculated using a power calculation software program for case-control genetic association analyses. Genomic DNA samples from a control group (n = 140) and from a case group of patients with prostate cancer (n = 164) were used for genotyping SNPs rs2660, rs1131454, and rs34137742 in all samples. Statistical analyses were performed using a logistic regression model.

RESULTS

A significant association was observed between the rs2660 genotype (A/G) and prostate cancer. Genotype AA increased the risk, whereas genotype GG decreased the risk of prostate cancer. The GG genotype was not observed in the African American samples. The AA genotype also increased the risk of prostate cancer with age.

CONCLUSIONS

The OAS1 SNP rs2660 AA genotype was associated significantly with prostate cancer, whereas the GG genotype protected against prostate cancer. OAS1 rs2660 may be a prostate cancer susceptibility polymorphism, which is a significant observation, especially in a context of the OAS1-RNaseL pathway. Thus, a functional defect in OAS1 because of the rs2660 SNP not only can attenuate RNaseL function but also can alter cell growth and apoptosis independent of RNaseL.

Abstract 4029: Inhibitor of differentiation 4 (Id4) Induces of senescence, apoptosis and cell cycle regression in prostate cancer

Id4 is a member of helix loop helix (HLH) transcriptional regulator family. Unlike its other family members (Id1, 2 and 3) that promote metastasis, proliferation and invasion (tumor promoter). Id4 essentially acts as a tumor suppressor e.g. Id4 expression is lost in prostate cancer through promoter hypermethylation. However the underlying mechanism by which Id4 acts as a tumor suppressor remains to be determined. In order to investigate the molecular mechanism by which Id4 acts as a tumor suppressor, we used DU145 cell in which Id4 is epigenetically silenced. Ectopic expression of Id4 in DU145 cells resulted in the induction of several cellular processes that are reminiscent of its role as a tumor suppressor. Our results suggested that Id4 is directly linked to cell cycle control, apoptosis, senescence and induction of epithelial like morphology. There is also an upregulation in androgen receptor expression, localization to the nucleus and an atypical response to androgens in DU145 prostate cancer cells. FACS analysis using a combination of PI and Annexin V staining demonstrated the ability of Id4 to induce an S-phase arrest, and initiate apoptosis. Interestingly, Id4 promoted senescence as observed by beta-galactosidase staining. RT-PCR and western blot analysis were used to study the gene expression of apoptosis and cell cycle control genes such as: E-cadherin, p21, p27, p53, MDM2, E2F1 and, Androgen receptor. The S-phase arrest in Du145+Id4 cells was E2F-1 dependent. The increased expression of E-cadherin, p27, p21 and MDM2 in DU145+Id4 cells strengthen the hypothesis that Id4 acts as a tumor suppressor by regulating key cell cycle control and apoptosis associated genes. Re-expression of functional androgen receptor marked a dramatic change in the androgen independent prostate cancer cell type. Thus, Id4 appears to induce a total cellular reprogramming and reversal of the cancer phenotype, by influencing key regulatory pathways.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4029. doi:10.1158/1538-7445.AM2011-4029

Abstract 2772: 2’-5’oligoadenylate synthetase polymorphism is associated with prostate cancer: Effect modified by age and race

Introduction: 2’ -5’ -oligoadenylate synthetase (2-5 OAS1) is an antiviral gene that converts ATP to a series of (2-5A). 2-5A promotes dimerization of latent ribonuclease (RNASE L) to form catalytically active RNASEL, a candidate hereditary prostate cancer gene. Thus a defect in OAS1 can not only attenuate RNASEL function, but can also alter cell growth and apoptosis independent of RNASEL. OAS1 polymorphism (rs2660) has been associated with increased disease susceptibility and viral infection like, HCV, West Nile virus infection, SARS, diabetes and MS. The AA genotype, known to have lower enzymatic activity promotes disease susceptibility whereas GG genotype with higher enzyme activity confers protection. In the present study we investigated this functional polymorphism (rs2660) in OAS1 in a large prostate cohort.

Methods: Genomic DNA from Buffy coat samples was used from age matched controls (n=140) and prostate cancer patients (n=164) who had undergone prostatectomy for genotyping. Information regarding age, race, and cancer stage were available for all samples. PCR-RFLP, followed by direct sequencing was used for genotyping. SNPs rs2660, rs1131454 and rs34137742 were genotyped on all samples. Statistical analysis was performed using chi2 test and logistic regression model with NCSS software.

Results: The rs2660 genotype distribution is summarized in table 1. Genotype AA increases the risk of prostate cancer by 61%. Prostate cancer incidence increases with age, however when combined with rs2660 genotype AA the odds of prostate cancer incidence are higher.SNPs rs1131454 and rs34137742 were not associated with prostate cancer.

Conclusion: OAS1 SNP rs2660 AA genotype is significantly associated with prostate cancer whereas GG genotype protects against prostate cancer. The effect of this genotype distribution was more profound in African American population as compared to Caucasians.

Abstract LB-141: Expression and localization of Id3 in human prostate cancer

Purpose: The inhibitor of differentiation (Id) proteins are dominant negative basic helix-loop-helix family of transcription factors that lack the DNA-binding basic domain but have intact HLH domain. The four members of the Id protein family (Id1-Id4) are known to play a critical role in the coordinated regulation of gene expression during cell growth, differentiation and tumorigenesis. Although in vitro studies have demonstrated the role of Id1 in regulating prostate cancer (PCa) cell proliferation, apoptosis and androgen independence, its clinical significance in PCa remains controversial. On the other hand there is lack of evidence on the expression of Id2 and Id3 in PCa progression. Studies have demonstrated that silencing of Id3 is significantly more effective in blocking proliferation of PCa cells as compared to Id1 whereas Id2 silencing has been primarily shown to be involved in apoptotic pathway. Hence in this study we re-evaluated the role of Id1 in PCa and extended our study to show that Id3 protein expression has better clinical relevance compared to Id1 and Id2 in PCa.

Experimental design: The expression of Id-1, -2 and -3 was determined by real time and Western blotting along with their sub-cellular localization by ICC in PCa cell lines LNCaP, DU145 and PC3. To assess their significance in prostate cancer progression, the protein expression was investigated in clinical prostate tumor samples on high density tissue microarray by IHC.

Results: The expression of Id1 and Id3 mRNA was low in LNCaP and DU145 as compared to PC3 whereas the level of Id2 expression was similar between all the PCa cell lines. The protein expression data was consistent with the mRNA levels in the PCa cell lines. All three Id's were primarily cytoplasmic with some nuclear presence. The IHC data showed a significant increase in the expression of Id1 and Id3 in clinical prostate tumor tissue samples compared to normal prostate tissue whereas Id2 showed elevated levels but was not significant as compared to Id1 and Id3. The expression of Id3 protein correlated with the Gleason grading and stage of PCa.

Conclusions: This is the first study demonstrating a correlation between increased expression of Id3 and prostate cancer progression. It also reconfirms and establishes the association of Id1with PCa. The results warrant further investigation into isoform specific effects of Id1and Id3 on prostate tumorigenesis. (Research Support: NIH/NCI RO1 CA128914 and NIH/NCRR/RCMI G12RR03062. The first two authors contributed equally to this work.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-141. doi:10.1158/1538-7445.AM2011-LB-141

Abstract 4026: Id4 acts as a tumor suppressor by regulating c-Myc and MDM2 in prostate cancer

PURPOSE: Id proteins (Id1, Id2, Id3, and Id4) function as dominant negative regulators of basic helix loop helix transcription factor family. They share the conserved HLH domain but lack the DNA binding basic domain. This domain configuration allows the Id proteins to dimerize with bHLH proteins. The Id-bHLH dimer therefore fails to bind the E box consensus sequence and activate transcription. In general Id1 and Id3 promote proliferation and inhibit differentiation and thus their expression is generally high in many cancers. The function of Id4 appears to be unique as compared to Id1-Id3. Recent studies have demonstrated that Id4 is epigenetically silenced in many cancers suggesting that Id4 may in fact act as a tumor suppressor. The present study was carried out to determine the molecular mechanism by which Id4 acts as a tumor suppressor in prostate cancer. DESIGN METHODS: Initial studies were carried out on DU145 cells in which Id4 is epigenetically silenced. Over-expression of Id4 decreased proliferation and promoted epithelial like morphology in DU145 cells. A proteomics based approach suggested that MDM2 is a potential downstream target of Id4. The upstream regulators and downstream targets of MDM2 were then evaluated to understand the mechanism and functional significance of Id4-MDM2 cross talk. RESULTS: A combination of expression and immuno-localization studies demonstrated that c-Myc and p14ARF, the upstream regulators of MDM2 expression are down-regulated in the presence of Id4. Id4 also significantly up-regulated the expression and nuclear localization of CDKNIs p21and p27. Unexpectedly, the expression of p53 a known target of MDM2 was decreased both at the transcript and protein level. CONCLUSIONS: Although MDM2 was discovered as a potential downstream target, our pathway analysis suggests that c-Myc could also be a downstream target of Id4. The de-repression of CDKNI appears to be c-Myc dependent but p53 independent primarily because in DU145 cells, p53 is mutated. Alternatively, decreased MDM2 could promote p21 stability resulting in increased nuclear localization and expression. Taken together our data support the role of Id4 as a potential tumor suppressor that is unique and opposite to the oncogenic properties of other HLH members Id1, Id2 and Id3.

Supported by: NIH/NCI R01CA128914 and NIH/NCRR/RCMI G12RR03062.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4026. doi:10.1158/1538-7445.AM2011-4026