-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