Association of TP53 Single Nucleotide Polymorphisms with Prostate Cancer in a Racially Diverse Cohort of Men

Growing evidence indicates the involvement of a genetic component in prostate cancer (CaP) susceptibility and clinical severity. Studies have reported the role of germline mutations and single nucleotide polymorphisms (SNPs) of TP53 as possible risk factors for cancer development. In this single institutional retrospective study, we identified common SNPs in the TP53 gene in AA and CA men and performed association analyses for functional TP53 SNPs with the clinico-pathological features of CaP. The SNP genotyping analysis of the final cohort of 308 men (212 AA; 95 CA) identified 74 SNPs in the TP53 region, with a minor allele frequency (MAF) of at least 1%. Two SNPs were non-synonymous in the exonic region of TP53: rs1800371 (Pro47Ser) and rs1042522 (Arg72Pro). The Pro47Ser variant had an MAF of 0.01 in AA but was not detected in CA. Arg72Pro was the most common SNP, with an MAF of 0.50 (0.41 in AA; 0.68 in CA). Arg72Pro was associated with a shorter time to biochemical recurrence (BCR) (p = 0.046; HR = 1.52). The study demonstrated ancestral differences in the allele frequencies of the TP53 Arg72Pro and Pro47Ser SNPs, providing a valuable framework for evaluating CaP disparities among AA and CA men.

Abstract 1449: Targeting CBP/p300 and its downstream transcriptional machinery in advanced prostate cancer

Prostate cancer (PCa) is the second leading cause of cancer-related deaths in men in the US. There is a largely unmet clinical need to identify and develop novel strategies, that work either alone or in concert with AR-directed therapeutics, to combat CRPC. The highly conserved histone acetyltransferases CBP/p300 are potent co-activators for AR, and high p300 expression is associated with locally advanced disease and castration-resistant AR function. This study shows that CBP and p300 are highly expressed and correlate closely with AR gene expression and AR activity score in primary PCa and CRPC. By employing clinically relevant PCa models, the clinical significance of CBP/p300 expression in PCa patients as well as mechanistic evaluation of CBP/p300 transcriptional reprogramming and DNA damage response pathways have been undertaken. The molecular response to CBP/p300 inhibition will be assessed to discern novel metrics for precision medicine for PCa patients to improve therapeutic efficacy. Previous studies have relied on non-specific compounds and genetic silencing to target CBP/p300. CCS1477 (inobrodib) is a first-in-class bromodomain inhibitor developed by Cell Centric and targeted to inhibit CBP/p300 mediated bromodomain activity, and thus regulate cell survival. Inhibition of the CBP/p300 bromodomain resulted in significant downregulation of AR-FL, AR-V7, and its targets’ mRNA expression, as well as inhibition of associated factors such c-MYC and its downstream targets, in multiple PCa models. Transcriptomic analysis indicated that both CBP and p300 expression correlate with expression of genes involved in double strand break (DSB) DNA repair process including homologous recombination (HR) and non-homologous end joining (NHEJ) in both primary PCa and CRPC models. CCS1477 directly impacted DNA damage response and repair dynamics, as shown via delay in time to resolution of DNA damage foci formation, including RAD51 and γH2AX foci. Inhibition of CBP/p300 activity decreased tumor cell proliferation, blocked CRPC xenograft growth in vivo, and decreased proliferation ex vivo in patient-derived prostate tumor explants. Importantly, CBP/p300 expression correlated with HR genes in human prostate tissue samples in different cohorts. Lastly, inhibition of CBP/p300 activity also decreased HR gene expression in patients further supporting the essential role CBP/p300 plays in DNA repair. In sum, CBP/p300 inhibition mediates HR repair and impacts patient outcome. In conclusion, these studies identify CBP/p300 as a driver of PCa tumorigenesis through coordinated control of critical transcriptional events and lay the groundwork to optimize therapeutic strategies for advanced PCa via CBP/p300 inhibition, potentially in combination with AR-directed therapies. Combined, these studies have the capacity for significant near-term impact in the prevention and/or management of metastatic disease.

Citation Format: Sumaira Sardar, Lakshmi Ravindranath, Christopher McNair, Saswati Chand, Wei Yuan, Denisa Bogdan, Jon Welti, Adam Sharp, Matthew Schiewer, Lisa Butler, Johann de Bono, Kris Frese, Nigel Brooks, Neil Pegg, Karen Knudsen, Ayesha Shafi. Targeting CBP/p300 and its downstream transcriptional machinery in advanced prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1449.

Germline mutation landscape of DNA damage repair genes in African Americans with prostate cancer highlights potentially targetable RAD genes

In prostate cancer, emerging data highlight the role of DNA damage repair genes (DDRGs) in aggressive forms of the disease. However, DDRG mutations in African American men are not yet fully defined. Here, we profile germline mutations in all known DDRGs (N = 276) using whole genome sequences from blood DNA of a matched cohort of patients with primary prostate cancer comprising of 300 African American and 300 European Ancestry prostate cancer patients, to determine whether the mutation status can enhance patient stratification for specific targeted therapies. Here, we show that only 13 of the 46 DDRGs identified with pathogenic/likely pathogenic mutations are present in both African American and European ancestry patients. Importantly, RAD family genes (RAD51, RAD54L, RAD54B), which are potentially targetable, as well as PMS2 and BRCA1, are among the most frequently mutated DDRGs in African American, but not in European Ancestry patients.

Abstract 2074: Germline mutation landscape of all DNA repair genes in African American prostate cancer patients

Introduction: DNA damage repair genes (DDRGs) play a critical role in genomic stability and their dysfunction contributes to mutagenesis in several cancer types. In prostate cancer (CaP) emerging data provide potential roles of DDR pathways in aggressive disease. However, the association with disease progression and therapeutic stratification based on inherited mutations of DDRGs remains to be defined in African American (AA) CaP patients. Our objective was to genomically profile all known annotated DDRGs in AA and Caucasian American (CA) CaP patient to determine whether DDRG germline variation status can refine patient stratification for targeted therapeutic options.

Methods: Germline mutations in all DDRGs (N=276) was evaluated by whole genome sequence (WGS) analysis of archived blood DNA samples from 600 CaP patients (300 AA and 300 CA) who underwent primary treatment at Walter Reed National Military Medical Center. The WGS mean coverage exceeded 37x. Principal Component Analysis (PCA) was used infer axes of genetic variation within AA men and examine individual and population clustering to predict ancestry of each sample using the Peddy program. Variant frequencies in CPDR CaP patients were compared to variant frequencies available from the Exome Aggregation Consortium (ExAC) control cases with no CaP by Fisher's Exact Test, using false discovery rate adjusted p-values.

Results: Interrogation of the complete known DDRG set of 276 genes revealed several known and novel mutations in this cohort. The Pathogenic/likely pathogenic (P/LP) variant carrier rate was higher than reported before (23.5%) in both AA and CA patients. However, the analysis revealed that more than 2/3 of the identified 47 DDRGs with P/LP mutation were different between AA and CA patients. Unlike in CA patients, several RAD family genes (RAD51, RAD54L, RAD54B), PMS2, and BRCA1 were among the most frequently mutated DDRGs in AA patients, but not in CA patients. The most frequent (over 1% carrier frequency) and potentially targetable type of mutations were independently validated by ddPCR. These genes are part of targetable DDRG pathways (homologous recombination and mismatch repair), suggesting that targeted therapy could potentially benefit AA patients. AA men harbor more potentially targetable DDRG germline mutations (over 10%) than CA men which may contribute to addressing CaP disparity. Germline mutations in any of the DDRG genes was associated with shorter time to BCR (Kaplan-Meier analysis, log rank p value 0.044) in AA patients, but not in CA patients.

Conclusion: Our findings highlight distinct racial differences in DDRGs and addresses the clinical utility by targeted therapy across AA and CA men. The percentage of patients with DDRG germline variation is of suitable threshold (23%) to consider early genetic testing for them in both AA and CA patients.

Citation Format: Indu Kohaar, Xijun Zhang, Shyh-Han Tan, Darryl Nousome, Kevin Babcock, Lakshmi Ravindranath, Gauthaman Sukumar, Elisa Mcgrath-Martinez, John Rosenberger, Camille Alba, Amina Ali, Denise Young, Yongmei Chen, Jennifer Cullen, Inger Rosner, Isabella Sesterhenn, Albert Dobi, Gregory Chesnut, Clesson Turner, Clifton Dalgard, Matthew Wilkerson, Shiv Srivastava, Gyorgy Petrovics. Germline mutation landscape of all DNA repair genes in African American prostate cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2074.

Abstract B075: Defining germline mutations of DNA damage repair genes in African American prostate cancer patients

Background: DNA damage repair genes (DDRGs) play a critical role in protecting genome integrity and have been implicated in several cancer types. In the context of prostate cancer (CaP) emerging data provide potential role of this pathway in aggressive disease. It has also been recently demonstrated that PARP inhibitors can extend overall survival in metastatic patients with DDRG mutations. However, the association and therapeutic stratification based on inherited mutations of DDRGs remains to be defined in African American (AA) CaP patients.

Our objective was to assess the frequency and association with disease aggressiveness of all known DDRGs in blood derived genomic DNAs of AA and Caucasian American (CA) CaP patients archived at the DOD Center for Prostate Disease Research and assess how this information can refine patient stratification for specific targeted therapeutic options.

Method: Germline mutations in all DDRGs was evaluated by whole genome sequence (WGS) analysis of archived blood DNA samples from 600 CaP patients (300 AA and 300 CA) who underwent primary treatment at Walter Reed National Military Medical Center (WRNMMC) over the past 20 years. These patients had equal access Department of Defense healthcare system with up to 20 years of follow-up time.

Following quality control steps to assess DNA quantity by Qubit assay and DNA quality by Bioanalyzer assay, DNA samples were used to generate PCR-free libraries for WGS using the NovaSeq (Illumina) platform. Out of the 600 libraries we generated, 14 dropped out, achieving a success rate of 97.6%. The successful libraries had an excellent quality based on DNA library metrics (yield and fragment length). Whole genome sequencing depth of the samples exceeded 37x on average and about 4 million SNPs were identified in the samples.

Patient genotypes were projected onto principal components from reference populations. Sample ancestries were predicted by using the “Peddy” program, which uses a machine learning model trained on individuals of diverse ancestries from the 1000 Genomes Project reference panel. Due to mismatched ancestry, 33 samples were excluded from further analyses. An additional 17 samples were excluded due to higher than minimal noise level based on analyses using “ContEst” tool from Broad GATK package and Illumina noise percent values.

Results: Interrogation of an inclusive DDRG set of 180 genes predicted to have non-silent effects on the protein sequence (e.g. missense, nonsense, frameshift) for germline mutations in this cohort revealed several known and novel mutations. The analysis has not been finalized yet. Mutation data will be assessed for association with the extensive available clinical and pathological data, including disease progression (metastasis), family history and African ancestry. Novel mutations, anticipated especially in the understudied AA context, will be analyzed for functional impact.

Citation Format: Kevin Babcock, Xijun Zhang, Matthew Wilkerson, Clifton L. Dalgard, Shyh-Han Tan, Lakshmi Ravindranath, Yongmei Chen, Jennifer Cullen, Shiv Srivastava, Inger L. Rosner, Gyorgy Petrovics. Defining germline mutations of DNA damage repair genes in African American prostate cancer patients [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B075.

Analysis of PMEPA1 Isoforms (a and b) as Selective Inhibitors of Androgen and TGF-β Signaling Reveals Distinct Biological and Prognostic Features in Prostate Cancer

Dysfunctions of androgen/TGF-β signaling play important roles in prostate tumorigenesis. Prostate Transmembrane Protein Androgen Induced 1 (PMEPA1) inhibits androgen and TGF-β signaling via a negative feedback loop. The loss of PMEPA1 confers resistance to androgen signaling inhibitors and promotes bone metastasis. Conflicting reports on the expression and biological functions of PMEPA1 in prostate and other cancers propelled us to investigate isoform specific functions in prostate cancer (PCa). One hundred and twenty laser capture micro-dissection matched normal prostate and prostate tumor tissues were analyzed for correlations between quantitative expression of PMEPA1 isoforms and clinical outcomes with Q-RT-PCR, and further validated with a The Cancer Genome Atlas (TCGA) RNA-Seq dataset of 499 PCa. Cell proliferation was assessed with cell counting, plating efficiency and soft agar assay in androgen responsive LNCaP and TGF-β responsive PC3 cells. TGF-β signaling was measured by SMAD dual-luciferase reporter assay. Higher PMEPA1-a mRNA levels indicated biochemical recurrence (p = 0.0183) and lower PMEPA1-b expression associated with metastasis (p = 0.0173). Further, lower PMEPA1-b and a higher ratio of PMEPA1-a vs. -b were correlated to higher Gleason scores and lower progression free survival rate (p < 0.01). TGF-β-responsive PMEPA1-a promoted PCa cell growth, and androgen-responsive PMEPA1-b inhibited cancer cell proliferation. PMEPA1 isoforms -a and -b were shown to be promising candidate biomarkers indicating PCa aggressiveness including earlier biochemical relapse and lower disease specific life expectancy via interrupting androgen/TGF-β signaling.

Molecular profiling of radical prostatectomy tissue from patients with no sign of progression identifies ERG as the strongest independent predictor of recurrence

BACKGROUND

As a major cause of morbidity and mortality among men, prostate cancer is a heterogenous disease, with a vast heterogeneity in the biology of the disease and in clinical outcome. While it often runs an indolent course, local progression or metastasis may eventually develop, even among patients considered "low risk" at diagnosis. Therefore, biomarkers that can discriminate aggressive from indolent disease at an early stage would greatly benefit patients. We hypothesized that tissue specimens from early stage prostate cancers may harbor predictive signatures for disease progression.

METHODS

We used a cohort of radical prostatectomy patients with longitudinal follow-up, who had tumors with low grade and stage that revealed no signs of future disease progression at surgery. During the follow-up period, some patients either remained indolent (non-BCR) or progressed to biochemical recurrence (BCR). Total RNA was extracted from tumor, and adjacent normal epithelium of formalin-fixed-paraffin-embedded (FFPE) specimens. Differential gene expression in tumors, and in tumor versus normal tissues between BCR and non-BCR patients were analyzed by NanoString using a customized CodeSet of 151 probes.

RESULTS

After controlling for false discovery rates, we identified a panel of eight genes (ERG, GGT1, HDAC1, KLK2, MYO6, PLA2G7, BICD1 and CACNAID) that distinguished BCR from non-BCR patients. We found a clear association of ERG expression with non-BCR, which was further corroborated by quantitative RT-PCR and immunohistochemistry assays.

CONCLUSIONS

Our results identified ERG as the strongest predictor for BCR and showed that potential prognostic prostate cancer biomarkers can be identified from FFPE tumor specimens.

Abstract 3296: Tumor antigens Fetuin-A and Secreted Protein Acidic and Rich in Cysteine (SPARC) Autoantibodies as diagnostic and prognostic biomarkers in prostate cancer

Introduction: Improvements in blood-based biomarkers for distinguishing between indolent and aggressive prostate cancer are critical in enhancing the management of the disease. To address this, we have focused on the quantification of autoantibodies (AAbs) against tumor antigens present in the sera of patients. We have selected SPARC and Fetuin-A (also known as Alpha 2-HS Glycoprotein [AHSG]) for analysis as they are shown to be highly expressed at late stages of prostate cancer. The objectives of this study are: 1) To measure AAbs against SPARC and Fetuin-A in the sera of prostate cancer patients; 2) To determine whether there is a correlation between levels of SPARC and Fetuin-A AAbs in serum, disease and race status.

Methods: Sera from prostate cancer patients and healthy controls were evaluated for AAbs against SPARC and Fetuin-A by using recombinant full-length proteins as substrates in an enzyme-linked immunosorbent assay (ELISA) assay. Sera from 117 Caucasian American (CA) n= and 111 African American (AA) prostate cancer patients with Gleason grades 6-10, and healthy controls (CA, n=52; AA, n=45) were analyzed in addition to sera from a biopsy cohort (n=99). The specificity of AAbs against the respective target proteins was confirmed by immunoblot analysis.

Results: SPARC AAbs were detected in the sera, with significantly lower levels in both CA (p&lt;0.0001; AUC=0.80), and AA prostate cancer patients (p&lt;0.0001; AUC=0.82), compared to healthy controls. AAbs against Fetuin-A were significantly lower in prostate cancer patients in comparison to controls (p&lt;0.0001; AUC=0.96). The range of AAb reactivity to SPARC and Fetuin-A was similar in both CA and AA prostate cancer patients. The results from biopsy cohort showed lower SPARC AAbs in cancer positive (n = 49) in comparison to cancer negative (n = 42) cases, and healthy controls.

Conclusions: In this study, we established the presence of AAbs against SPARC in prostate cancer patient serum for the first time. More importantly, we observed highly significant differences between prostate cancer patient (low) and controls (high) sera, across different ethnic groups, similar to AAbs noted against Fetuin-A. These data support the further evaluation of SPARC and Fetuin-A AAbs as promising serum biomarkers for prostate cancer.

Note: This abstract was not presented at the meeting.

Citation Format: Shyh-Han Tan, Andy Martinez, Anshu Rastogi, Wei Huang, Sreedatta Banerjee, Lakshmi Ravindranath, Denise Young, Amina Ali, Indu Kohaar, Yongmei Chen, Jennifer Cullen, Gyorgy Petrovics, Albert Dobi, David G. McLeod, Jacob Kagan, Sudhir Srivastava, Isabell A. Sesterhenn, Inger L. Rosner, Shiv Srivastava, Alagarsamy Srinivasan. Tumor antigens Fetuin-A and Secreted Protein Acidic and Rich in Cysteine (SPARC) Autoantibodies as diagnostic and prognostic biomarkers in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3296.

Abstract B008: PMEPA1 isoform specific regulation of androgen and TGF beta signaling in prostate cancer

Introduction and Objectives: The dysfunctions of androgen receptor (AR) and TGF-β signaling contribute to prostate tumorigenesis and cancer progression. Our laboratory has identified PMEPA1 as an androgen responsive gene with prostate abundance, as well as PMEPA1/NEDD4 and AR negative feedback loop in the regulation of AR levels in prostate cancer cells. In addition, it has also been established by other groups that PMEPA1 inhibits TGF-β signaling via a similar negative feedback loop as a TGF-β responsive gene. Five isoforms are transcribed from distinct promoters within the PMEPA1 locus. PMEPA1 isoforms were shown to have variations at the N-terminus of the protein. This study focuses on understanding of the expression and biologic functions of PMEPA1 isoforms in CaP.

Methods: The PMEPA1 isoforms were evaluated for expressions in multiple CaP cell lines, trensfectant derivatives, and prostate tumors. LNCaP cells were treated with R1881 (0, 0.1, 1.0 nM) and DU-145 and PC-3 cells were treated with TGF-β (0, 5 and 25 ng/ml) for 24 hours. PMEPA1 isoform specific plasmids and siRNAs were transfected into LNCaP, DU-145, and PC-3 cells individually. Cell proliferation was analyzed by cell counting, cell plating efficiency assay, and soft agar assay. The protein levels of PMEPA1 isoforms, AR, PSA, TGF-β receptor I, Smad2 were detected by immunoblotting, and the transcript levels of KLK3 (PSA), TGF-β responsive genes including THBS1, NEDD9 and COL1A1 were evaluated by QRT-PCR. The TGF-β signaling activity was measured by SMAD reported dual-luciferase assay. The transcript levels of PMEPA1-252, PMEPA3-287-STAG1, AR, PSA in 120 matched human benign and malignant frozen tissue were evaluated with Q-PCR.

Results: The expressions of PMEPA1-252 and PMEPA2-344 isoforms were restricted to androgen-responsive prostate cancer cells in comparison to broader expression pattern of other isoforms (PMEPA3-287/STAG1, PMEPA4-259 and PMEPA5-237). The expression of PMEPA1-2 was androgen regulated, whereas expression of PMEPA 3-5 was regulated by TGF-β. Only PMEPA1-252 inhibited cell growth of LNCaP, DU-145 and PC-3 cells. In contrast, PMEPA2-4 promoted cell growth of DU-145 and PC-3 cells. Only PMEPA1-252 mediated AR protein degradation and inhibited AR signaling. In contrast, PMEPA3-287-STAG1 and PMEPA4-259 inhibited TGF-β signaling luciferase activity and transcript levels of THBS1, NEDD9 and COL1A1. All PMEPA1 isoforms were found to have no effects on protein level of TGF-β receptor I. Moreover, the deletion mutants of N-terminus and transmembrane domains interrupted the isoform specific inhibitory effects on AR/TGF-β signaling. The transcript level of PMEPA1-252 was higher than PMEPA3-287-STAG1 in benign prostate tissue. Different from PMEPA1-252, the expression of PMEPA3-287-STAG1 was not found to decrease in prostate tumor tissue. There was no significant correlation between the expression of PMEPA1-252 and PMEPA3-287-STAG1 in prostate tissue. The transcript of PMEPA1-252 was associated with PSA, but the expression of PMEPA3-287-STAG1 was found not to be associated with PSA or AR in CaP cells.

Conclusions: The PMEPA isoforms appear to underscore distinct biologic functions in the context of androgen and TGF-β signaling. Intensively studied PMEPA1-252 was specific for AR degradation in prostate cancer cells and was consistent with previous observations of association of AR upregulation with loss of PMEPA1 in prostate cancer. The roles of PMEPA1 isoforms need to be better defined in prostate cancer and other cancers.

Funding: This study was supported by CPDR, USUHS, HU0001-10-2-0002 to I.L.R.

Citation Format: Hua Li, Shashwat Sharad, Lakshmi Ravindranath, Gyorgy Petrovics, Yongmei Chen, Alagarsamy Srinivasan, Inger Rosner, Albert Dobi, Shiv Srivastava. PMEPA1 isoform specific regulation of androgen and TGF beta signaling in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr B008.

Abstract A013: Prostate cancer gene expression panel to address racial differences of molecular alterations in prostate cancer

Introduction and Objectives: Prostate cancer (CaP) affects 1 in 7 men in their lifetime. African American (AA) men have significantly higher incidence and mortality from CaP compared to Caucasian American (CA) men. Emerging data, including ours, have described significantly lower frequencies of alterations in common CaP driver genes (ERG and PTEN) in AA men as compared to CA men. We have also noted that genes commonly overexpressed in CaP (ERG, AMACR, PCA3), and currently used as diagnostic markers, exhibit much lower frequency and more heterogeneity in AA men. The goal of this study was to define a CaP marker panel that is overexpressed equally well in AA and CA CaPs.

Methods: Three platforms (RNA-Seq, NanoString, and qRT-PCR) were used for evaluating CaP-associated gene expression in CA and AA patients (N=144). Candidate genes with robust tumor overexpression (over 4-fold) in CaP in paired normal and tumor specimens from AA and CA patients were selected from NanoString and RNA-Seq data for validation by qRT-PCR (TaqMan) in laser microdissected (LCM) tumor and benign cells of frozen tissue sections (50 CA and 35 AA). An assay protocol (gene specific RT and preamplification followed by TaqMan PCR) was developed for noninvasive early detection of candidate genes in regular urine (non-DRE) using urinary exosomal RNA.

Results: Tumor transcriptomes of CA patients consistently revealed elevated expression of PCA3 and AMACR. However, these genes had variable overexpression in the AA cohort. The top genes that were similarly overexpressed in tumors of AA and CA patients were validated by qRT-PCR in LCM tumor and normal epithelial cells (N=85). At least one gene of a six-gene signature (DLX1, HOXC4, NKX2-3, COL10A1, HOXC6, and PSGR) was overexpressed in tumor cells of all AA and CA cases, providing a consistent ethnicity-informed tumor expression signature, which was further validated in silico in TCGA RNA-Seq data. Urinary exosome-based assay was developed and optimized for PSGR, DLX1, HOXC4, NKX2-3, as well as PCA3, PCGEM1, and ERG. All markers have been evaluated in a prospective cohort of 100 patients. In 36 AA patients a sensitivity of 78%, specificity of 68%, and AUC of 0.83 was achieved, surpassing currently used urine CaP markers of ERG and PCA3 in this cohort.

Conclusions: A CaP tissue-based gene expression marker panel has been defined with potential diagnostic utility for both CA and AA men in the context of urinary exosomes.

Source of Funding: This study is supported by NCI/EDRN ACN12011-001-0 and NCI RO1 CA162383-05 grants to S.S.

Citation Format: Indu Kohaar, Sreedatta Banerjee, Lakshmi Ravindranath, Yongmei Chen, Amina Ali, Jacob Kagan, Sudhir Srivastava, Albert Dobi, David McLeod, Inger Rosner, Shiv Srivastava, Gyorgy Petrovics. Prostate cancer gene expression panel to address racial differences of molecular alterations in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A013.

Abstract B42: Development of a urine exosome-based prostate cancer gene expression panel to address racial differences in prostate cancer

Introduction: Prostate cancer (CaP) is the most prevalent cancer and third leading cause of cancer death among men in United States, with an anticipated 161,360 newly diagnosed cases and approximately 26,730 deaths in 2017. It is estimated that 1 in 6 men of African ancestry will be diagnosed with prostate cancer in their lifetime in comparison with 1 in 8 men of Caucasian origin. One of the major risk factors for the development of CaP is race/ethnicity. African American (AA) men have significantly higher incidence and mortality from CaP compared to Caucasian American (CA) men. Emerging data, including ours, have described significantly lower frequencies of alterations in common CaP driver genes (ERG and PTEN) in AA men as compared to CA men. We have also noted that genes commonly overexpressed in CaP (ERG, AMACR, PCA3), and currently used as diagnostic markers, exhibit much lower frequency and more heterogeneity in AA men. The goal of this study was to define a CaP marker panel that is overexpressed equally well in AA and CA CaP.

Methods: RNA-seq, NanoString, and qRT-PCR platforms were used for evaluation of CaP-associated gene expression in CA and AA patients (N=144). Candidate genes with robust tumor overexpression (over 4-fold) in CaP in paired normal and tumor specimens from AA and CA patients were selected from Nanostring and RNA-seq datasets for validation by TaqMan based qRT-PCR approach in laser microdissected (LCM) tumor and benign cells of frozen tissue sections (50 CA and 35 AA). An assay protocol based on gene-specific RT and preamplification followed by TaqMan PCR was developed for noninvasive early detection of candidate markers in regular patient urine (non-DRE) using urinary exosomal RNA.

Results: Tumor transcriptomes of CA patients consistently revealed overexpression of PCA3 and AMACR. However, these genes had variable overexpression in AA cohort. The top genes that were similarly over expressed in tumors of AA and CA patients were further validated by qRT-PCR in LCM tumor and normal epithelial cells (N=85). At least one gene of a six-gene signature (DLX1, HOXC4, NKX2-3, COL10A1, HOXC6, and PSGR) was overexpressed in tumor cells of all AA and CA cases, providing a consistent ethnicity-informed tumor-expression signature, which was further validated in silico in TCGA RNA-seq data. Urinary exosome-based assay was developed and optimized for PSGR, DLX1, HOXC4, NKX2-3, as well as PCA3 and ERG. Sensitivity and specificity of the marker panel in a feasibility cohort (N=40) with optimal cutoff for the urine marker panel was 78% and 65%, respectively. Evaluation of the assay performance in CA and AA patients in a prospective independent cohort of 100 patients is ongoing.

Conclusion: An ethnicity-informed CaP tissue-based gene expression marker panel has been defined with potential diagnostic utility for both CA and AA men in the context of urinary exosomes.

Citation Format: Indu Kohaar, Sreedatta Banerjee, Lakshmi Ravindranath, Yongmei Chen, Amina Ali, Jacob Kagan, Sudhir Srivastava, Albert Dobi, David McLeod, Inger L. Rosner, Shiv Srivastava, Gyorgy Petrovics. Development of a urine exosome-based prostate cancer gene expression panel to address racial differences in prostate cancer [abstract]. In: Proceedings of the Tenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2017 Sep 25-28; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2018;27(7 Suppl):Abstract nr B42.

Abstract 1230: Association of common germline variants with TMPRSS2-ERG gene fusion status in prostate cancer

Introduction and Objectives: Oncogenic activation of ERG resulting from prevalent gene fusions (predominantly as TMPRSS2-ERG) is a key driver event in prostate cancer (CaP) pathogenesis. Our laboratory and others have recently reported that major cancer driver genes, including ERG, show significant racial/ethnic differences in CaP. It is present in two thirds of CaP patients of European Ancestry including Caucasian Americans (CA) but is present at lower frequencies in African Americans (AA), Africans and Asians. Racial differences of CaP associated SNPs have also been extensively described. However, there is limited data on germline association with ERG fusion status. The goal of this study is to identify germline molecular determinants associating with ERG status of CaP. Methods: Blood derived genomic DNA samples were prepared from 270 AA men and 130 CA men treated by radical prostatectomy. ERG status was determined by immuno-histochemistry (IHC) for ERG protein expression. SNP genotyping was performed on the Illumina Golden Gate platform using Infinium Oncoarray SNP chip. Data analysis approaches included association analyses based on EMMAX and imputation analysis by IMPUTE2. SNP genotyping was performed using droplet digital polymerase chain reaction (ddPCR) approach Results: SNP genotyping analysis was performed in 321 patients with 478,299 SNPs. We identified SNPs associated with ERG status using EMMAX analysis. The SNPs most significantly (p &lt;10-5) associated with ERG fusion status included rs6698333, an intron variant of Kruppel-like factor 17 (KLF17) and two SNPs (rs1889877, rs3798999) in the intron of adhesion G protein-coupled receptor B3 (ADGRB3). 4 SNPs (rs10215144, rs3818136, rs9380660 and rs1792695) were found to be significantly (p &lt;10-5) associated with ERG positive phenotype under any tumor foci positive for the fusion. Fine-mapping of SNPs by genotype imputation analysis (IMPUTE2) using the 1000 Genomes reference dataset, found rs34349373 and rs2055272 to be significantly associated (p &lt;10-7). The 2 variants were found to be in strong linkage disequilibrium (LD) in both CA and AA populations with r2 of 1.0 and 0.91 respectively. Imputed SNP rs2055272 was further experimentally evaluated by Taqman based ddPCR SNP genotyping approach. Concordance between Taqman genotypes and imputed genotypes was found to be 98.04%. Association analysis of the SNPs with clinico-pathological features of CaP and functional annotation of the significant SNPs by in silico eQTL based analysis are being performed. Conclusions: This study identified SNPs associated with ERG status of CaP, a major driver oncogene in CaP. Although the biological significance as it relates to ERG status of CaP still needs to be determined, these SNPs, with independent validation, may help as markers in stratifying patients early (even before CaP is detected) for targeted prevention and treatment options.

Citation Format: Indu Kohaar, Yongmei Chen, Lakshmi Ravindranath, Denise Young, Amina Ali, Qiyuan Li, Albert Dobi, Inger L. Rosner, Isabell Sesterhenn, Jennifer Cullen, Matthew Freedman, Shiv Srivastava, Gyorgy Petrovics. Association of common germline variants with TMPRSS2-ERG gene fusion status in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1230.

Abstract 5352: Racial/ethnic differences in prostate cancer genomic alterations

Background: Distinct biology of prostate cancer (CaP) among men of different races and ethnicities have been recently highlighted. Along these lines higher frequencies of the most common CaP gene alterations, ERG proto-oncogene activation and deletion of the PTEN tumor suppressor, have been reported among Caucasian Americans (CA) when compared to other racial/ethnic groups. We have reported the cumulative analyses of CaPs from 435 patients (whole genome sequencing (WGS), FISH evaluations and SNP arrays) that highlighted the recurrent deletion and disease progression association of the Limbic System-Associated Membrane Protein (LSAMP) in CaP genomes of African American (AA) men. Further examination of these data indicated the AA CaP genome associated recurrent deletion of the Chromodomain Helicase DNA Binding Protein 1(CHD1) gene.

Methods: Combined evaluation of frequencies and prognostic associations of ERG oncoprotein by immunohistochemistry and deletions of LSAMP, CHD1 and PTEN genes by FISH were performed using a multi-core TMA (42 AA and 59 CA patients) with longitudinal follow up data (median 16 years). CaP and matched blood genomic DNA samples (N=60) from AA patients were analyzed by WGS. ERG frequencies were further evaluated in index tumors of Chinese CaPs (N=100) and were compared to ERG frequencies in index tumors of AA (N=336) and CA (N=594) patients.

Results: Frequent deletions of CHD1 (29% AA vs. 10% CA p=0.017) and LSAMP (26% AA vs. 7% CA, p=0.006) were found in AA CaPs by FISH assay. Both of these deletions were associated with rapid disease progression. Evaluation of CaPs by WGS further highlighted the recurrent deletion of CHD1 among AA men. Comparative evaluation of ERG (AA, N=336; CA, N=594, and Asian N=100) underscored highest ERG frequencies among CA patients (49.3%) followed by AA (23.2%) and Chinese (22%) men.

Conclusions: In light of distinct biology of CaPs in ethnically/racially diverse CaP patient populations there is a need for developing broadly applicable diagnostic, prognostic marker panels and therapeutic approaches. Recurrent CHD1 deletion in CaPs of AA patients may provide new therapeutic opportunities in light of recent reports suggesting that CaP patients harboring CHD1 deletion may benefit from PARP inhibitor or platinum agents therapies. Funding: This study was supported by CPDR, USUHS, HU0001-10-2-0002 to I.L.R., the NCI/EDRN IAA ACN12011-001-0 to S.S. and by the NCI R01CA162383 to S.S.

Citation Format: Albert Dobi, Gyorgy Petrovics, Shyh-Han Tan, Hua Li, Denise Young, Cara Schafer, Jesse Fox, Kevin Babcock, Heng-Cheng Hu, Gauthaman Sukumar, Yingjie Song, Lakshmi Ravindranath, Yongmei Chen, Joseph Cheng, Reinhard Ebner, Qingyu Xiao, Yidi Sun, Yixue Li, Yuan Ji, Jun Hou, Wendy Wang, Guo-Ping Zhao, Jacob Kagan, Sudhir Srivastava, Joel T. Moncur, Clifton L. Dalgard, Matthew Wilkerson, Inger L. Rosner, Jennifer Cullen, Matthew Freedman, Zoltan Szallasi, Isabell A. Sesterhenn, Shiv Srivastava. Racial/ethnic differences in prostate cancer genomic alterations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5352.

Abstract 1806: Distinct PMEPA1 gene isoforms regulate androgen-responsive or TGF-β-responsive prostate cancers

Introduction: PMEPA1 gene has been defined as androgen and TGF-β responsive gene to inhibit AR and TGF-β signaling via negative feedback loops. Our previous studies identified five PMEPA1 isoforms (PMEPA1-252, PMEPA1-287, PMEPA1-237, PMEPA1-259 and PMEPA1-344) in prostate cancer (CaP) cell lines and CaP RNA-Seq data. PMEPA1-252 decreased androgen receptor (AR) protein levels, suppressed AR signaling and inhibited CaP cell growth. In contrast, PMEPA1-287 and PMEPA1-259 inhibited the transcript levels of TGF-β responsive genes and promoted CaP cell growth. Previous studies showed that knockdown of PMEPA1 gene in PC-3 cells facilitated bone metastasis via activating TGF-β signaling and increasing bone metastasis associated genes. In this study, we further study the roles of PMEPA1 isoforms in the context androgen resistance and bone metastasis process in CaP.

Methods: The expression vectors harboring PMEPA1 isoforms were transfected into DU-145 and PC-3 cells. The protein levels of PMEPA1 isoforms, TGF-β receptor I, SMAD2 and 3 were detected by immunoblotting. The TGF-β signaling activity was measured by SMAD reported dual-luciferase assay in DU-145 and PC-3 cells. The transcript levels of PMEPA1 isoforms and AR or TGF-β responsive genes including KLK3 (PSA), THBS1, NEDD9, bone metastasis associated genes, such as SPARC, CTGF, IL11 and PTHRP were assessed by quantitative PCR (Q-PCR).

Results: PMEPA1-287 and PMEPA1-259 inhibited SMAD reporter activity in DU-145 and PC-3 cells. No PMEPA1 isoform was found to down-regulate the protein levels of TGF-β receptor I and SMAD2 and 3. Increased TGF-β signaling was detected in androgen independent LAPC4-AI and C4-2B cells. In contrast, AR signaling and PMEPA1-252 increased in C4 cells, but not in C4-2 and C4-2B cells. Decreased transcript level of PMEPA1-259 was detected in C4-2 and C4-2B cells, while PMEPA1-287 was found to decrease in C4-2 cells but increase in C4-2B and LAPC4-AI cells. No significant changes of transcript levels of PMEPA1-344 and PMEPA1-237 were detected. In 120 matched human benign and malignant frozen prostate tissues, only PMEPA1-252 associated with SPARC showing inverse correlation. The expression of SPARC was not responsive to either androgen or TGF-β in CaP cells, but increase significantly in C4-2B cells compared to LNCaP cells. These findings suggested PMEPA1 isoforms drive bone metastasis and androgen resistance development via interrupting AR/TGF-β signaling and bone metastasis associated genes.

Conclusions: Our results provide a plausible explanation for the dual function of PMEPA1 gene through its alternative isoforms in the process of prostate cancer progression from androgen dependent to TGF-β dependent/androgen resistant stages of the disease. These findings may lead to new therapeutic opportunities in standard hormone ablation and TGF-β targeted therapies of CaP.

Citation Format: Hua Li, Shashwat Sharad, Lakshmi Ravindranath, Gyorgy Petrovics, Yongmei Chen, Inger L. Rosner, Albert Dobi, Shiv Srivastava. Distinct PMEPA1 gene isoforms regulate androgen-responsive or TGF-β-responsive prostate cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1806.

Identification of a Small Molecule That Selectively Inhibits ERG-Positive Cancer Cell Growth

Oncogenic activation of the ETS-related gene (ERG) by recurrent gene fusions (predominantly TMPRSS2-ERG) is one of the most validated and prevalent genomic alterations present in early stages of prostate cancer. In this study, we screened small-molecule libraries for inhibition of ERG protein in TMPRSS2-ERG harboring VCaP prostate cancer cells using an In-Cell Western Assay with the highly specific ERG-MAb (9FY). Among a subset of promising candidates, 1-[2-Thiazolylazo]-2-naphthol (NSC139021, hereafter ERGi-USU) was identified and further characterized. ERGi-USU selectively inhibited growth of ERG-positive cancer cell lines with minimal effect on normal prostate or endothelial cells or ERG-negative tumor cell lines. Combination of ERGi-USU with enzalutamide showed additive effects in inhibiting growth of VCaP cells. A screen of kinases revealed that ERGi-USU directly bound the ribosomal biogenesis regulator atypical kinase RIOK2 and induced ribosomal stress signature. In vivo, ERGi-USU treatment inhibited growth of ERG-positive VCaP tumor xenografts with no apparent toxicity. Structure-activity-based derivatives of ERGi-USU recapitulated the ERG-selective activity of the parental compound. Taken together, ERGi-USU acts as a highly selective inhibitor for the growth of ERG-positive cancer cells and has potential for further development of ERG-targeted therapy of prostate cancer and other malignancies.Significance: A highly selective small-molecule inhibitor of ERG, a critical driver of early stages of prostate cancer, will be imperative for prostate cancer therapy. Cancer Res; 78(13); 3659-71. ©2018 AACR.

Abstract 4649: Development of an ethnicity informed gene expression panel with potential to improve prostate cancer diagnosis

Introduction and Objectives: Prostate cancer (CaP) affects 1 in 7 men throughout their life time. One of the major risk factors for the development of CaP is race/ethnicity. African American (AA) men have significantly higher incidence and mortality from CaP compared to Caucasian American (CA) men. Emerging data including ours have described significantly lower frequencies of alterations in the common CaP driver genes (ERG and PTEN) in AA men as compared to CA men. We have also noted that genes commonly overexpressed in CaP (ERG, AMACR and PCA3), and currently used as diagnostic markers, exhibit much lower frequency and more heterogeneity in AA men. The goal of this study was to define a broader CaP marker panel that is overexpressed equally well in AA and CA CaP.

Methods: Three platforms (RNASeq, NanoString and QRT-PCR) were used for evaluation of CaP associated gene expression in CA and AA patients (N=144). Candidate genes with robust tumor overexpression (over 4-fold) in CaP in comparison of paired normal and tumor specimens from AA and CA patients were selected from the Nanostring and RNASeq data for validation by QRT-PCR (TaqMan) in laser microdissected (LCM) tumor and benign cells of frozen tissue sections (50 CA and 35 AA). An assay protocol (gene specific pooled RT and pre-amplification followed by TaqMan PCR) was set up for the noninvasive early detection of candidate genes in regular patient urine (non-DRE) using RNA derived from urinary exosomes.

Results: As expected tumor transcriptomes of CA patients revealed consistently elevated expression of PCA3 and AMACR genes. However, these genes had variable overexpression in AA cohort. The top genes that were similarly over expressed in tumors of AA and CA patients were validated by real time QRT-PCR (TaqMan) analysis in LCM dissected tumor and normal epithelial cells (N=85). At least one gene of a six gene signature (DLX1, HOXC4, NKX2-3, COL10A1, HOXC6 and PSGR) was overexpressed in tumor cells of all AA and CA cases, providing a consistent ethnicity informed tumor expression signature, which was further validated in silico in TCGA RNASeq data. Urinary exosome based assay was developed and optimized for PSGR, DLX1, HOXC4, NKX2-3, as well as PCA3 and ERG. Sensitivity and specificity with optimal cutoff for the urine marker panel was 71% and 61% respectively (N=40). Evaluation of the assay performance in CA and AA patients in a prospective independent cohort of 100 patients addressing race specific performance is in progress.

Conclusions: A CaP tissue based gene expression marker panel has been defined with potential diagnostic utility for both CA and AA men in the context of urinary exosomes.

Citation Format: Indu Kohaar, Lakshmi Ravindranath, Sreedatta Banerjee, Yongmei Chen, Amina Ali, Yingjie Song, Jacob Kagan, Sudhir Srivastava, Albert Dobi, David McLeod, Inger L. Rosner, Shiv Srivastava, Gyorgy Petrovics. Development of an ethnicity informed gene expression panel with potential to improve prostate cancer diagnosis [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 4649. doi:10.1158/1538-7445.AM2017-4649

Abstract 1290: Association of common genetic variants with TMPRSS2 ERG fusion status in prostate cancer

Introduction and Objectives: Oncogenic activation of ERG resulting from prevalent gene fusions is present in two thirds of prostate cancer (CaP) patients of European Ancestry including Caucasian Americans (CA). Our laboratory and others have recently reported that major cancer driver genes, including ERG, show significant racial/ethnic differences in CaP with lower frequencies in African Americans (AA), Africans and Asians. Racial differences of CaP associated SNPs have also been extensively described. However, there is limited data on germline association with ERG fusion status. The goal of this study is to identify germline molecular determinants associating with ERG status of CaP.

Methods: Blood derived genomic DNA samples were prepared from 270 AA men and 129 CA men treated by radical prostatectomy at Walter Reed National Military Medical Center (WRNMMC). ERG status was determined in whole mounted prostate specimens by immuno-histochemistry (IHC) for ERG protein expression as a surrogate for the TMPRSS2-ERG fusion. Blinded blood samples were genotyped for SNPs on the Illumina Golden Gate platform using Infinium Oncoarray, a 500K genome wide BeadChip kit from Illumina. Data analysis approaches included association analyses based on logistic regression, Principal Component Analysis (PCA) and Efficient Mixed-Model Association eXpedited (EMMAX) analysis. Genotype imputation analysis is being performed by IMPUTE2 program.

Results: After applying rigorous sample and SNP QC steps on the datasets, SNP genotyping analysis was performed in 321 patients with 478,299 SNPs. Logistic regression, principal component analysis by EIGENSTRAT and a variance component approach, EMMAX analysis were performed to account for population structure. By EMMAX we identified SNPs associated with ERG status. The SNPs most significantly (&lt;10-5) associated with ERG fusion status included rs6698333, an intron variant of Kruppel-like factor 17 (KLF17) and two SNPs (rs1889877, rs3798999) in the intron of adhesion G protein-coupled receptor B3 (ADGRB3). Fine-mapping of SNPs is underway by genotype imputation analysis (IMPUTE2) using the 1000 Genomes reference dataset, followed by independent validation.

Conclusions: This study identified SNPs differentially associated with ERG status of CaP, a major driver oncogene in CaP. Although the biological significance as it relates to ERG status of CaP still needs to be determined, these SNPs, with independent validation, may help as markers in stratifying patients early (even before CaP is detected) for targeted prevention and treatment options.

Citation Format: Indu Kohaar, Lakshmi Ravindranath, Denise Young, Amina Ali, Qiyuan Li, Albert Dobi, David McLeod, Inger L. Rosner, Isabell Sesterhenn, Matthew Freedman, Shiv Srivastava, Gyorgy Petrovics. Association of common genetic variants with TMPRSS2 ERG fusion status in prostate cancer [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 1290. doi:10.1158/1538-7445.AM2017-1290

Abstract 2830: Secreted protein acidic and rich in cysteine antigen and autoantibodies in sera of prostate cancer patients: Potential use in diagnosis /prognosis

Objectives: Improvements in blood based biomarkers for detecting clinically significant prostate cancer (CaP) or for distinguishing between indolent and aggressive CaP are critical in enhancing the management of this most common non-skin cancer of men in the US. These biomarkers include tumor associated antigens (TAAs) and autoantibodies (AAbs) against TAAs in patient sera. SPARC/Osteonectin is highly expressed in metastatic cancers (glioblastoma, melanoma, breast cancer and prostate cancer) and promotes bone metastasis and epithelial-mesemchymal transition. Our comparative transcriptome analyses of well/moderately differentiated CaP with poorly differentiated CaP, defined SPARC as central node in the network of genes with common regulatory elements (NKXH_NKXH_HOX) associating with poorly differentiated CaP. Further, we reported associations of high levels of SPARC mRNA or protein with Gleason 8-10 or poorly differentiated primary tumors and association with metastatic progression. The aims of this study are: i) Quantify SPARC antigen in the sera CaP patients; ii) Are AAbs against SPARC present in the serum of CaP patients?; iii) Is there a correlation between SPARC AAb level in patient sera and disease status? iii) Does SPARC AAb level vary according to distinct ethnic groups?

Methods: Sera from CaP patients and healthy controls were evaluated for SPARC antigen using a commercial enzyme-linked immunosorbent assay (ELISA) kit. AAbs against SPARC were determined by ELISA utilizing recombinant full-length human SPARC protein as a substrate. For evaluation we used Caucasian American (CA, n=117) and African American (AA, n=111) CaP patients comprising Gleason 6-10, and healthy controls (CA, n=52; AA, n=45).

Results: SPARC antigen levels in the sera showed a difference in the overall case versus control groups (p=0.0016) and this trend was observed only in AA (p=0.0015) in comparison to CA patients (p=0.1709). SPARC AAbs were detected in the sera and the values were significant in the overall case versus control (p&lt; .0001) and also in CA (p&lt;.0001) and AA (p&lt;.0001) CaP patients with levels significantly lower in patients compared to controls. AAb reactivity for CaP patients was similar between CA and AA groups.

Conclusions: This study demonstrated the presence of AAbs against SPARC in CaP patient serum for the first time. Of note, highly significant differences were noted between CaP patient (low) and controls (high) sera, across different ethnic groups. These data suggest further evaluation of SPARC AAbs as a promising serum biomarker for CaP.

Source of Funding: This research was supported by the Center for Prostate Disease Research, Uniformed Services University Grant HU0001-10-2-0002.

Citation Format: Anshu Rastogi, Andy Martinez, Amina Ali, Shyh-Han Tan, Jennifer Cullen, Yongmei Chen, Gyorgy Petrovics, Albert Dobi, Lakshmi Ravindranath, Denise Young, Isabell Sesterhenn, Jacob Kagan, Sudhir Srivastava, David McLeod, Inger Rosner, Shiv Srivastava, Alagarsamy Srinivasan. Secreted protein acidic and rich in cysteine antigen and autoantibodies in sera of prostate cancer patients: Potential use in diagnosis /prognosis [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 2830. doi:10.1158/1538-7445.AM2017-2830

Abstract 1183: Structure-activity studies and biological evaluations of ERGi-USU, a highly selective inhibitor for ERG-positive prostate cancer cells

Introduction and objectives: While new prostate cancer (CaP) treatments (Abiraterone and Enzalutamide) have improved survival in castration-resistant prostate cancer (CRPC), their benefits are short-lived and drug resistance develops likely due to numerous adaptive mutations. Therefore it is a critical to develop effective novel inhibitors to target other signaling pathways that promote or contribute to prostate tumorigenesis. Accumulating evidence has established the androgen regulated TMPRSS2-ERG fusion as a common oncogenic driver that contributes to the early development and progression of over half of CaP. Therefore, ERG oncoprotein and ERG dependent pathways are promising targets for CaP therapy in early stages when cancer is most responsive to treatment. We previously identified a small molecule inhibitor, ERGi-USU, which selectively inhibits ERG protein and cell growth in ERG positive tumor cell lines and mouse xenograft models. In an effort to further develop ERGi-USU with enhanced efficacy we performed detailed structure-activity relationship (SAR) evaluation of ERGi-USU core structure and developed new derivatives.

Methods: Based on SAR of the core structure of ERGi-USU, 48 new derivatives were designed and synthesized by substitutions with alkyl, alkoxy, cycloalkyl, heterocycloalkyl, aryl, heteroaryl or hydroxyl groups. The new ERGi-USU derivatives were evaluated for inhibition of cell growth and ERG protein levels in the TMPRSS2-ERG fusion harboring CaP cell line, VCaP. Four of these compounds have been selected for evaluation of ERG selectivity by defining IC50 in ERG positive malignant cells (VCaP, KG1, MOLT-4 and COLO320), ERG negative CaP cell line (LNCaP) or ERG positive normal primary endothelium-derived cells (HUVEC).

Result: Like parental compound, four new ERGi-USU derivatives exhibited inhibition of cell growth and ERG protein levels in ERG positive VCaP, KG1, MOLT-4 and COLO320 cell lines, with no or minimal effects on LNCaP and HUVEC cells. One of the new derivatives (ERGi-USU#6) showed increased efficacy for cell growth inhibition (IC50=0.074µM) compared to the parental ERGi-USU (IC50=0.200µM). Other three new compounds showed similar IC50 as the ERGi-USU.

Conclusion: Comprehensive evaluation of ERGi-USU derivatives along with parental compound has continued to underscore selective inhibition of ERG positive tumor cells by these small molecules.

Citation Format: Ahmed A. Mohamed, Charles P. Xavier, Gauthaman Sukumar, Samuel D. Banister, Vineet Kumar, Shyh-Han Tan, Shilpa Katta, Lakshmi Ravindranath, Muhammad Jamal, Taduru Sreenath, David G. McLeod, Gyorgy Petrovics, Albert Dobi, Meera Srivastava, Sanjay Malhotra, Clifton Dalgard, Shiv Srivastava. Structure-activity studies and biological evaluations of ERGi-USU, a highly selective inhibitor for ERG-positive prostate cancer cells [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 1183. doi:10.1158/1538-7445.AM2017-1183

Synergistic Activity with NOTCH Inhibition and Androgen Ablation in ERG-Positive Prostate Cancer Cells

The oncogenic activation of the ETS-related gene (ERG) due to gene fusions is present in over half of prostate cancers in Western countries. Because of its high incidence and oncogenic role, ERG and components of ERG network have emerged as potential drug targets for prostate cancer. Utilizing gene expression datasets, from matched normal and prostate tumor epithelial cells, an association of NOTCH transcription factors with ERG expression status was identified, confirming that NOTCH factors are direct transcriptional targets of ERG. Inhibition of ERG in TMPRSS2-ERG-positive VCaP cells led to decreased levels of NOTCH1 and 2 proteins and downstream transcriptional targets and partially recapitulated the phenotypes associated with ERG inhibition. Regulation of NOTCH1 and 2 genes by ERG were also noted with ectopic ERG expression in LNCaP (ERG-negative prostate cancer) and RWPE-1 (benign prostate-derived immortalized) cells. Furthermore, inhibition of NOTCH by the small-molecule γ-secretase inhibitor 1, GSI-1, conferred an increased sensitivity to androgen receptor (AR) inhibitors (bicalutamide and enzalutamide) or the androgen biosynthesis inhibitor (abiraterone) in VCaP cells. Combined treatment with bicalutamide and GSI-1 showed strongest inhibition of AR, ERG, NOTCH1, NOTCH2, and PSA protein levels along with decreased cell growth, cell survival, and enhanced apoptosis. Intriguingly, this effect was not observed in ERG-negative prostate cancer cells or immortalized benign/normal prostate epithelial cells. These data underscore the synergy of AR and NOTCH inhibitors in reducing the growth of ERG-positive prostate cancer cells.Implications: Combinational targeting of NOTCH and AR signaling has therapeutic potential in advanced ERG-driven prostate cancers. Mol Cancer Res; 15(10); 1308-17. ©2017 AACR.

Autoantibodies against oncogenic ERG protein in prostate cancer: potential use in diagnosis and prognosis in a panel with C-MYC, AMACR and HERV-K Gag

Overdiagnosis and overtreatment of prostate cancer (CaP) is attributable to widespread reliance on PSA screening in the US. This has prompted us and others to search for improved biomarkers for CaP, to facilitate early detection and disease stratification. In this regard, autoantibodies (AAbs) against tumor antigens could serve as potential candidates for diagnosis and prognosis of CaP. Towards this, our goals were: i) To investigate whether AAbs against ERG oncoprotein (overexpressed in 25-50% of Caucasian American and African American CaP) are present in the sera of CaP patients; ii) To evaluate an AAb panel to enhance CaP detection. The results using an enzyme-linked immunosorbent assay (ELISA) showed that anti-ERG AAbs are present in a significantly higher proportion in the sera of CaP patients compared to healthy controls (p = 0.0001). Furthermore, a panel of AAbs against ERG, AMACR and human endogenous retrovirus-K Gag successfully differentiated CaP patient sera from healthy controls (AUC = 0.791). These results demonstrate for the first time that anti-ERG AAbs are present in the sera of CaP patients. In addition, the data also suggest that AAbs against ERG together with AMACR and HERV-K Gag may be a useful panel of biomarkers for diagnosis and prognosis of CaP.

Abstract 140: LSAMP gene deletion is associated with rapid disease progression in prostate cancer of African American men

INTRODUCTION: Disproportionately higher rates of prostate cancer (CaP) incidence and mortality have been reported among African American (AA) men. Although oncogenic TMPRSS2-ERG gene fusion and deletion of the PTEN tumor suppressor gene are established cancer driver gene alterations in CaP, they are known to be more prevalent among men of European ancestry. By utilizing carefully annotated specimens, this study focused on the discovery of recurrent genomic alterations in CaP of AA men in comparison to Caucasian Americans (CA).

METHODS: Genomic DNA from clinically localized primary prostate tumors (Gleason 6 or 7 with primary pattern 3) and matched peripheral blood lymphocytes of seven AA and seven CA patients, were analyzed by paired-end sequencing on Illumina Genome Analyzer IIx to a depth of 30x. Following alignment to reference genome, somatic alterations on tumor DNA that include single nucleotide variants (SNVs), insertion and deletions (Indels), structural variations, copy number variations, and inter- and intra-chromosomal translocations of tumor DNA sequence were identified. To confirm prevalent genomic deletions we performed FISH analysis on a tissue microarray constructed from 42 AA and 59 CA tumor and normal samples of an independent cohort. Frequently deleted loci were further validated by analysis of TCGA CaP SNP array data from 41 AA and 279 CA prostate tumors.

RESULTS: A comparative evaluation of whole genome sequences of AA and CA CaP revealed a prevalent deletion of the LSAMP locus of chromosome 3q13.31 in AA CaP. These observations were confirmed by SNP array and FISH assays in independent cohorts of specimens. AA CaP patients with LSAMP deletion showed rapid disease progression. In contrast to higher frequency of LSAMP deletion, significantly lower frequencies of PTEN and ERG alterations were noted in CaP of AA men. Furthermore, CaP genomes of AA men displayed a higher rate of inter-chromosomal rearrangements than those from CA men.

CONCLUSIONS: We highlight distinct features of AA and CA CaP genomes including common CaP driver genes (TMPRSS2- ERG, PTEN) and define a novel recurrent deletion of the LSAMP locus. This study underscores the need for careful evaluations of cancer genomes in underrepresented populations in the global context with implications for precision medicine strategies.

Citation Format: Albert Dobi, Gyorgy Petrovics, Hua Li, Shyh-Han Tan, Tanja Stümpel, Denise Young, Shilpa Katta, Qiyuan Li, Kai Ying, Bernward Klocke, Lakshmi Ravindranath, Indu Kohaar, Yongmei Chen, Dezső Ribli, Korbinian Grote, Hau Zou, Joseph Cheng, Clifton L. Dalgard, Shimin Zhang, István Csabai, Jacob Kagan, David Takeda, Massimo Loda, Sudhir Srivastava, Matthias Scherf, Martin Seifert, Timo Gaiser, David G. McLeod, Zoltan Szallasi, Reinhard Ebner, Thomas Werner, Isabell A. Sesterhenn, Matthew Freedman, Shiv Srivastava. LSAMP gene deletion is associated with rapid disease progression in prostate cancer of African American men. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 140.

Abstract 4958: Immunobiomarkers: novel autoantibody panel comprising oncogenic ERG, C-MYC, AMACR and HERV-K Gag for the detection of prostate cancer

INTRODUCTION: Biomarkers for early detection as well as disease stratification are a major area of focus in prostate cancer (CaP) research. Autoantibodies against a large array of tumor associated antigens (TAAs) have been noted in a diverse number of cancers, including CaP. Since autoantibodies represent humoral responses elicited in response to TAAs expressed in tumor cells, it is likely that autoantibodies could serve as diagnostic/prognostic markers for CaP. Hence, the present study addresses the following: i) Are autoantibodies against ERG, an oncogene frequently overexpressed in CaP, present in the sera of patients?; ii) Does a multiplex autoantibody panel containing ERG, AMACR, C-MYC, and HERV-K Gag improve the detection of CaP?

METHODS: Sera from 50 CaP patients positive for ERG expression and 50 patients negative for ERG expression, along with 50 healthy control subjects were analyzed. Purified recombinant protein for ERG, AMACR, and C-MYC as well as synthetic peptides corresponding to epitopes in ERG and HERV-K Gag were used in an enzyme-linked immunosorbent assay (ELISA) developed in our laboratory to detect autoantibodies in the sera of CaP patients. In addition, a luciferase immunoprecipitation assay (LIPS), involving a chimeric luciferase-ERG protein, was used as an independent assay to test the presence of anti-ERG autoantibodies.

RESULTS: Analysis of patient sera by ELISA revealed significantly higher detection of autoantibodies against ERG (P = 0.0001), AMACR (P &lt; 0.0001), C-MYC (P = 0.0013), and HERV-K Gag (P &lt; 0.0001) proteins in CaP cases compared to healthy controls. The specificity of anti-ERG autoantibodies was supported by a competitive ELISA assay. Further, the LIPS assay was also able to detect anti-ERG autoantibodies in patient sera. In addition, a multiplex panel assay involving ERG, AMACR, and HERV-K Gag greatly improved the detection of true positive CaP cases (AUC = 0.792).

CONCLUSIONS: Here we demonstrated that autoantibodies against ERG are present in the sera of prostate cancer patients through ELISA analysis. In addition, utilizing a panel of genes for autoantibody detection, consisting of ERG, AMACR, and HERV-K Gag, showed high specificity for CaP cases. These promising findings suggest the diagnostic potential of autoantibodies and similar autoantibody panels in enhancing CaP diagnosis.

Source of Funding: Center for Prostate Disease Research, Uniformed Services University Grant HU0001-10-2-0002, NCI/EDRN Grant ACN12011-001-0, and the National Cancer Institute Grant R01CA162383.

Citation Format: Anshu Rastogi, Amina M. Ali, Sreedatta Banerjee, Lakshmi Ravindranath, Gyorgy Petrovics, Shyh-Han Tan, Jennifer Cullen, Yongmei Chen, Denise Young, Isabell A. Sesterhenn, Jacob Kagan, Sudhir Srivastava, David G. McLeod, Shiv Srivastava, Alagarsamy Srinivasan. Immunobiomarkers: novel autoantibody panel comprising oncogenic ERG, C-MYC, AMACR and HERV-K Gag for the detection of prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4958.

Abstract A35: Increased expression of PCGEM1 lncRNA in prostate cancer of African American men

Introduction: Prostate cancer (CaP) affects 1 in 7 men throughout their life time. One of the major risk factors for the development of CaP is race/ethnicity. African American (AA) men have significantly higher incidence and mortality from CaP compared to Caucasian American (CA). Our laboratory and others have recently described that cancer driver genes, including ERG and PTEN, have significantly different frequencies in AA versus CA CaP. In recent years progress has been made in evaluating the expression and role of long noncoding RNAs (lncRNAs) in prostate tumorigenesis, but variations in lncRNAs expression across race/ethnicity (AA vs CA) remains poorly understood. The objective of this study is to compare the expression of CaP related lncRNAs among AA and CA men.

Methods: Whole-mounted prostate sections from 30 patients, 15 AA and 15 CA matched for age, Gleason score and pathologic stage, were evaluated for the expression of lncRNAs that have been reported to be associated with CaP or other cancers. Probe sets were designed for the following 20 lncRNAs: CTBP1-AS, PCA3, PRNCR1, Hoxa11as, H19, HOTTIP, MEG3, PCGEM1, ST7OT1, SChLAP1, ANRIL/p15AS/CDK2BAS, HOTAIR, SRA-1/SRA, MALAT1/NEAT2, GAS5/SNHG2, PlncRNA-1/CBR3-AS1, Xist, hY1/RNY1, hY3/RNY3, PCAT-1. Tumor and benign epithelium was dissected under microscope from the slides, and the isolated RNA, passing BioAnalyzer quality control, was evaluated by using Nanostring platform. PCGEM1 expression analysis was updated in an existing QRT-PCR dataset of 88 patients (24 AA and 64 CA).

Results: Copy numbers of each gene, normalized to ten housekeeping genes, was compared between tumor and matched normal prostate epithelium and across ethnic groups. We have identified a panel of lncRNAs (CTBP1-AS, PCA3, PCAT-1, PRNCR1) overexpressed in tumor versus matched normal samples in 95% of patients when combined. Three genes were significantly downregulated in CaP (MEG3, HOTTIP, H19). Most significantly, PCGEM1 had robust overexpression in prostate tumors (over 10-fold upregulation) only in AA patients (7 of 15) but not in CAs (0 of 15), which was in concordance with evaluation of PCGEM1 in existing dataset, underscoring selective overexpression in AA CaP.

Conclusions: PCGEM1 was robustly overexpressed only in AA patients, whereas several lncRNAs were overexpressed (CTBP1-AS, PCA3, PCAT-1, PRNCR1) or downregulated (MEG3, HOTTIP, H19) in tumors of both AA and CA patients. Biomarker potential and biological functions of PCGEM1 are under further investigation.

Citation Format: Jocelyn Lee, Muhammad Jamal, Wusheng Yan, Denise young, Yingjie Song, Yongmei Chen, Shilpa Katta, Lakshmi Ravindranath, Alagarsamy Srinivasan, Jennifer Cullen, Jacob Kagan, Sudhir Srivastava, Albert Dobi, Inger L. Rosner, David G. McLeod, Isabell A. Sesterhenn, Shiv Srivastava, Gyorgy Petrovics. Increased expression of PCGEM1 lncRNA in prostate cancer of African American men. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr A35.

A novel genomic alteration of LSAMP associates with aggressive prostate cancer in African American men

Evaluation of cancer genomes in global context is of great interest in light of changing ethnic distribution of the world population. We focused our study on men of African ancestry because of their disproportionately higher rate of prostate cancer (CaP) incidence and mortality. We present a systematic whole genome analyses, revealing alterations that differentiate African American (AA) and Caucasian American (CA) CaP genomes. We discovered a recurrent deletion on chromosome 3q13.31 centering on the LSAMP locus that was prevalent in tumors from AA men (cumulative analyses of 435 patients: whole genome sequence, 14; FISH evaluations, 101; and SNP array, 320 patients). Notably, carriers of this deletion experienced more rapid disease progression. In contrast, PTEN and ERG common driver alterations in CaP were significantly lower in AA prostate tumors compared to prostate tumors from CA. Moreover, the frequency of inter-chromosomal rearrangements was significantly higher in AA than CA tumors. These findings reveal differentially distributed somatic mutations in CaP across ancestral groups, which have implications for precision medicine strategies.

Abstract 5058: Silencing of NOTCH signaling enhances the sensitivity of ERG positive prostate cancer cells to AR inhibitors

Introduction: Androgen receptor (AR) signaling plays a critical role in all the stages of prostate cancer (CaP) ranging from organ confined to castration-resistant (CRPC) phases. Although androgen deprivation therapy (ADT) remains the mainstay treatment for advanced CaP, the inevitable transition from androgen- sensitive to CRCP presents the most significant challenge in CaP therapy. Androgen dependent expression of oncogenic ETS related gene (ERG) in half of all CaP in western countries plays critical role in the tumorigenesis of CaP through regulation of cancer specific signaling pathways. We found that NOTCH transcription factors are common targets of ERG in ERG positive cancer cells. NOTCH signaling pathway is an important signaling pathway in the development of drug-resistant tumor growth. In the current study we evaluated the combinatorial effects of NOTCH and AR inhibitors in the context of ERG positive prostate cancer cells.

Methods: ERG, NOTCH1, NOTCH2 and downstream targets of NOTCH transcription factors were analyzed by Western blot assays. Dose and time kinetics of combining NOTCH inhibitor (γ-Secretase inhibitor 1, GSI-1) and AR inhibitors (Bicalutamide, Enzalutamide, and Abiraterone) were assessed in a panel of ERG positive or ERG negative CaP cells. Trypan blue exclusion, methylthiazole tetrazolium (MTT), or ApoTox-Glo™ Triplex assays were used to asses cell proliferation, apoptosis and drug cytotoxicity.

Results: Prostate cancer cell lines with endogenous or ectopic expression of ERG showed upregulation of NOTCH1 and NOTCH2. The NOTCH inhibitor, GSI-1 conferred an increased sensitivity to all tested AR inhibitors (Bicalutamide, Enzalutamide, and Abiraterone) with bicalutamide showing the most robust inhibition of AR, ERG, NOTCH1, NOTCH2, PSA, decreased cell growth and enhanced apoptosis in ERG positive VCaP cells. This observation was not seen in ERG negative LNCaP cells or in ERG positive primary endothelial cells.

Conclusions: NOTCH inhibitor enhanced sensitivity of AR inhibitors in ERG positive VCaP cells growth. The combination of the GSI-1 with AR inhibitors has shown synergistic effect when compared to single agent treatment. Taken together, our study suggests that NOTCH inhibitors may enhance the actions of AR inhibitors in the treatment of ERG positive prostate cancers. Inhibition of AR and NOTCH signaling may offer new opportunities in assessing ERG targeted therapy for prostate cancer.

Citation Format: Ahmed A. Mohamed, Shyh-Han Tan, Shilpa Katta, Charles P. Xavier, Lakshmi Ravindranath, Wei Huang, Hua Li, Meera Srivastava, Shashwat Sharad, Taduru Sreenath, Gyorgy Petrovics, Albert Dobi, Shiv Srivastava. Silencing of NOTCH signaling enhances the sensitivity of ERG positive prostate cancer cells to AR inhibitors. [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 5058. doi:10.1158/1538-7445.AM2015-5058

Abstract 4679: Silencing of PMEPA1, a NEDD4 E3 ubiquitin ligase binding protein, stabilizes androgen receptor and confers resistance to AR inhibitors

INTRODUCTION: The androgen receptor (AR) dysfunctions contribute to prostate cancer (CaP) development and progression. Earlier we defined the regulation of AR protein levels by a negative feed-back loop between AR and the androgen regulated PMEPA1, a NEDD4 E3 ubiquitin ligase binding protein. Our data also revealed decreased or absent PMEPA1 transcripts in 65% prostate tumors. This study focuses on the relationship of PMEPA1 protein with AR and its transcriptional targets (PSA) in human CaP, as well as the impact of PMEPA1 silencing on growth of PMEPA1-shRNA LNCaP cells derived tumors in naïve and castrated nude mice.

METHODS: Ten weeks old athymic Ncr-nu/nu mice were evaluated for the growth of tumor xenografts derived from PMPEA1-shRNA LNCaP (N = 20) and control-shRNA LNCaP cells (N = 20). Each mouse received 4×106 cells by subcutaneous injection to right flank side. The mice with tumors were castrated at 9th week post-injection. The tumor sizes were monitored twice per week until 16th week post-injection. The xenograft tissues were assayed by immunohistochemical (IHC) staining for PMEPA1, AR and PSA protein levels. The AR, PMEPA1 and PSA expressions in whole mount human prostate specimens were evaluated by IHC staining and QRT-PCR.

RESULTS: The PMEPA1 shRNA-LNCaP and control shRNA-LNCaP cells started to form subcutaneous tumors at 4 weeks after injections. However, the growth rate of PMEPA1 shRNA-LNCaP derived tumors was significantly faster than control derived tumors (P&lt;0.05). PMEPA1 shRNA-LNCaP tumors expressed higher levels of AR and PSA proteins as assessed by IHC. At 7 weeks after castration the tumor sizes increased by 69% in the control group in contrast to 304% in the PMEPA1-shRNA harboring xenografts (P&lt;0.05). In human CaP, decreased PMEPA1 mRNA expression significantly correlated with increased levels of AR transcription target PSA, as a surrogate for elevated AR. Focally increased PSA and AR protein levels were detected in a subset of low PMEPA1 expressing tumors.CONCLUSIONS: PMEPA1 silencing in CaP cells leads to gain of AR, increased tumor growth with potential to induce resistance to AR inhibition targeted therapy. Decreased PMEPA1 in human CaP correlated with increased AR activity. Thus, monitoring PMEPA1 expression in CaP cells offers new opportunities in therapeutic stratification of CaP. Further, restoring PMEPA1 in CaP cells may provide a new strategy for AR degradation focused therapy.

Citation Format: Hua Li, Elizabeth Umeda, Yingjie Song, Denise Young, Lakshmi Ravindranath, Ahmed Mohamed, Shashwat Sharad, Gyorgy Petrovics, David McLeod, Isabell Sesterhenn, Taduru Sreenath, Albert Dobi, Shiv Srivastava. Silencing of PMEPA1, a NEDD4 E3 ubiquitin ligase binding protein, stabilizes androgen receptor and confers resistance to AR inhibitors. [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 4679. doi:10.1158/1538-7445.AM2015-4679

Abstract 623: Evaluation of a multiplex biomarker assay for the detection of prostate cancer cells in urine

Background and Objectives: Over one million men undergo prostate biopsies annually in the US, a majority of them due to elevated serum PSA. More than half of the biopsies turn out to be negative for prostate cancer (CaP). The limitations of PSA test as well as the biopsy procedure have prompted to develop more precise CaP detection assays in urine- (e.g. PCA3, TMPRSS2-ERG) or blood (e.g. PHI, 4K). Here we describe the development and evaluation of a Urine CaP Marker Panel (UCMP) assay for sensitive and reproducible detection of CaP cells in post-digital rectal examination (post-DRE) urine.

Methods: The cellular content of the post-DRE urine, was captured on translucent membrane for direct evaluation by microscopy and immunocytochemistry. The membranes placed on Cytoclear microscope slides were used for characterization of prostate epithelial cell by PSA and Prostein or tumor cells by ERG and AMACR protein markers. Immunostained cells were analyzed for quantitative and qualitative features and correlated with biopsy positive and negative status for malignancy.

Results: Assay was optimized for single cell capture sensitivity and downstream evaluations by spiking known number of cells from established prostate cancer cell lines, LNCaP and VCaP, into cleared control urine. The cells captured from the post-DRE urine of subjects, obtained prior to biopsy procedure, were co-stained for ERG, AMACR, Prostein and PSA, rendering a whole cell based analysis and characterization. A feasibility cohort of 63 post-DRE urine specimens was assessed. Comparison of the UCMP results with the blinded biopsy results showed an assay sensitivity of 64% (16 of 25) and a specificity of 68.8% (22 of 32) for CaP detection by biopsy.

Conclusion: This pilot study assessing a minimally invasive prostate cancer detection assay with single cell sensitivity cell-capture and characterization from the post-DRE urine holds promise for further development of this novel assay platform.

Citation Format: Kristen Nickens, Amina Ali, Tatiana Scoggin, Shyh-han Tan, Lakshmi Ravindranath, David McLeod, David Tacha, Isabell Sesterhenn, Albert Dobi, Shiv Srivastava, Gyorgy Petrovics. Evaluation of a multiplex biomarker assay for the detection of prostate cancer cells in urine. [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 623. doi:10.1158/1538-7445.AM2015-623

Abstract 4341: Distinct expression of PMEPA1 and its isoform, STAG1 in prostate cancer

Introduction and Objectives: We have defined a feedback loop model for the regulation of androgen receptor (AR) degradation by the hormone inducible PMEPA1 through NEDD4 E3 ubiquitin ligase in prostate cancer (CaP). The characterization of PMEPA1 at the mRNA levels indicated five isoforms transcribed from distinct promoters within the PMEPA1 locus. Analysis of the amino acid sequences of all PMEPA1 isoforms indicated variations at the N- and/or C- termini of the protein. Based on the prediction algorithms, PMEPA1 is classified as a type 1b transmembrane protein. In order to better understand the role of PMEPA1 in CaP, this study focuses on comparative analyses of the two most abundant isoforms of PMEPA1 in human CaPs.

Methods: Androgen responsive LNCaP and VCaP cells were used to evaluate the expression levels of annotated PMEPA1 isoforms by quantitative RT-PCR and by RNA-Seq. For validating of the two most abundant forms, the isoform 1 (Solid Tumor Associated Gene 1, STAG1) and the isoform 2 (PMEPA1), prostate tumor and benign epithelial cells were laser capture microdissected (LCM) from frozen OCT embedded prostate tissue. Total RNA was isolated from the LCM samples of 117 matched normal and prostate tumor specimens (N = 234) and were analyzed by TaqMan-based QRT-PCR for PMEPA1 isoform-1(STAG1) and isoform 2 (PMEPA1), AR and PSA. Correlation of the gene expression data with clinical and pathological characteristics, including biochemical recurrence (BCR) were examined by Kaplan-Meier survival and Cox proportional hazard model analyses.

Results: We have identified four mRNAs transcribed from the PMEPA1 locus in VCaP and LNCaP transcriptomes. Among these, STAG1 was highly expressed followed by PMEPA1 in both VCaP and LNCaP cells. In CaP patients tumor (T) over normal (N) mRNA expression of STAG1 did not have significant correlation with transcript levels of PMEPA1, AR or PSA. Patients with increased STAG1 mRNA level had a shorter time to BCR in a Kaplan-Meier analysis (P = 0.018). The correlation of increased STAG1 expression in tumor cells with increased chance for BCR was supported by multivariable Cox proportional hazard model (P = 0.0015; HR = 4.3).

Conclusions: As expected from the distinct transcription initiation origin, there were no significant correlation between the T/N expression of PMEPA1 (isofom 2) and STAG1 in human CaP specimens. Intriguingly, STAG1 (isoform 1) expression was an independent predictor of BCR after radical prostatectomy that warrants further investigations.

Keywords: PMEPA1, STAG1, AR, prostate cancer, biochemical recurrence

Funding: This study was supported by NIH grant, CA106653 to SS and AD and CPDR, USUHS, HU0001-10-2-0002 to DGM.

Citation Format: Hua Li, Lakshmi Ravindranath, Yongmei Chen, Shashwat Sharad, Allissa Dillman, Alargarsamy Srinivasan, David G. McLeod, Isabell A. Sesterhenn, Albert Dobi, Shiv Srivastava, Gyorgy Petrovics. Distinct expression of PMEPA1 and its isoform, STAG1 in prostate cancer. [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 4341. doi:10.1158/1538-7445.AM2015-4341

Prostate cancer marker panel with single cell sensitivity in urine

BACKGROUND

Over one million men undergo prostate biopsies annually in the United States, a majority of whom due to elevated serum PSA. More than half of the biopsies turn out to be negative for prostate cancer (CaP). The limitations of both the PSA test and the biopsy procedure have led to the development for more precise CaP detection assays in urine (e.g., PCA3, TMPRSS2-ERG) or blood (e.g., PHI, 4K). Here, we describe the development and evaluation of the Urine CaP Marker Panel (UCMP) assay for sensitive and reproducible detection of CaP cells in post-digital rectal examination (post-DRE) urine.

METHODS

The cellular content of the post-DRE urine was captured on a translucent filter membrane, which is placed on Cytoclear slides for direct evaluation by microscopy and immuno-cytochemistry (ICC). Cells captured on the membrane were assayed for PSA and Prostein expression to identify prostate epithelial cells, and for ERG and AMACR to identify prostate tumor cells. Immunostained cells were analyzed for quantitative and qualitative features and correlated with biopsy positive and negative status for malignancy.

RESULTS

The assay was optimized for single cell capture sensitivity and downstream evaluations by spiking a known number of cells from established CaP cell lines, LNCaP and VCaP, into pre-cleared control urine. The cells captured from the post-DRE urine of subjects, obtained prior to biopsy procedure, were co-stained for ERG, AMACR (CaP specific), and Prostein or PSA (prostate epithelium specific) rendering a whole cell based analysis and characterization. A feasibility cohort of 63 post-DRE urine specimens was assessed. Comparison of the UCMP results with blinded biopsy results showed an assay sensitivity of 64% (16 of 25) and a specificity of 68.8% (22 of 32) for CaP detection by biopsy.

CONCLUSIONS

This pilot study assessing a minimally invasive CaP detection assay with single cell sensitivity cell-capture and characterization from the post-DRE urine holds promise for further development of this novel assay platform. Prostate 75: 969-975, 2015. © 2015 The Authors. The Prostate, published by Wiley Periodicals, Inc.

Abstract 5566: Functional new insights into the regulation of the androgen receptor by PMEPA1/NEDD4-1 in prostate cancer

Introduction: Androgen receptor (AR) stability has been shown to be regulated by MDM2 E3 ubiquitin ligase. Our data suggest a role for PMEPA1 and NEDD4-1 in the regulation of AR protein in prostate cancer cells. The AR inducible PMEPA1 recruits NEDD4-1, an E3 ubiquitin ligase, to degrade AR. Decreased or absent PMPEA1 was observed in more than 65% of prostate tumors. PMEPA1 depleted transfectant is established in LNCaP cells with a shRNA lentivirus system and shown elevated AR protein levels, AR signaling and increased cell growth. In the current study, we investigated the growth and AR signaling of PMEPA1 depleted prostate cancer cells in the presence of AR inhibitors. Also we investigated the role of PMEPA1 silencing by DNA methylation in the regulation of AR.

Methods: PMEPA1 depleted LNCaP cells were treated with AR inhibitors (MDV3100 or bicalutamide) in the presence or absence of the synthetic androgen R1881. Cell growth was monitored by cell counting, BrdU incorporation, colony plating and soft agar assays. Cell cycle was analyzed with propidium iodide staining based flowcytometry. AR, PMEPA1, PSA proteins were assessed by immunoblot assay. Methylation of the PMEPA1 gene was evaluated in LCM-enriched tumor samples by combing precipitation of methylated-DNA and methylation-sensitive restriction enzyme digestion (COMPARE-MS). The transcript levels of PMEPA1 gene was assessed by qRT-PCR.

Results: PMEPA1 depleted LNCaP cells are more resistance to growth inhibition by MDV3100 or bicalutamide in both hormone and hormone-depleted conditions, which demonstrated stronger BrdU incorporation abilities, cell plating efficiency and colony formation capacities in soft agar under MDV3100 or bicalutamid treatment compared to controls. The half life of AR was increased, and more cells in S-phase and less apoptotic cells in PMEPA1 depleted LNCaP cells. Methylation of PMEPA1 gene and mRNA levels showed significant correlation in prostate tumors (n=77, P=0.001). The higher frequency of PMEPA1 gene methylation was noticed in Caucasian American patients.

Conclusions: PMEPA1 depleted prostate cancer cells develop increased resistance to AR inhibitors through enhanced AR signaling. Silencing of PMEPA1 may contribute to AR activation in prostate cancer. These data highlight that PMEPA1 deficiency may confer resistance to AR inhibitors during prostate cancer progression.

This study is supported by the NIH grant (R01CA106653) to SS.

Citation Format: Hua Li, Shashwat Sharad, Lakshmi Ravindranath, Michael Haffner, Daniel Heidenberg, Srinivasan Yegnasubramanian, Yongmei Chen, Ahmed Mohamed, Alagarsamy Srinivasan, Gyorgy Petrovics, Shiv Srivastava. Functional new insights into the regulation of the androgen receptor by PMEPA1/NEDD4-1 in prostate cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5566. doi:10.1158/1538-7445.AM2014-5566

Methylation of the PMEPA1 gene, a negative regulator of the androgen receptor in prostate cancer

The prostate transmembrane protein androgen induced 1 (PMEPA1) gene is highly expressed in prostate epithelial cells and is a direct transcriptional target for the androgen receptor (AR). AR protein levels are controlled by the AR-PMEPA1 negative feedback loop through NEDD4-E3 ligase. Reduced expression of PMEPA1 observed in prostate tumors, suggests that loss of PMEPA1 may play critical roles in prostate tumorigenesis. This study focuses on epigenetic mechanisms of reduced PMEPA1 expression in the cancer of the prostate (CaP). Benign (n = 77) and matched malignant (n = 77) prostate epithelial cells were laser capture micro-dissected from optimum cutting temperature embedded frozen prostate sections from 42 Caucasian American (CA) and 35 African American (AA) cases. Purified DNA specimens were analyzed for CpG methylation of the PMEPA1 gene. PMEPA1 mRNA expression levels were evaluated by qRT-PCR. Analysis of PMEPA1 methylation and mRNA expression in the same tumor cell populations indicated a significant inverse correlation between mRNA expression and methylation in CaP (P = 0.0115). We noted higher frequency of CpG methylation within the evaluated first intronic region of the PMEPA1 gene in prostate tumors of CA men as compared with AA. In CaP cell lines, PMEPA1 expression was induced and AR protein levels were diminished in response to treatment with the DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (decitabine). Cell culture-based studies demonstrated that decitabine restores PMEPA1 expression in AR-positive CaP cell lines. This report reveals the potential role of PMEPA1 gene methylation in the regulation of AR stability. Thus, downregulation of PMEPA1 may result in increased AR protein levels and function in CaP cells, contributing to prostate tumorigenesis.

Elevated osteonectin/SPARC expression in primary prostate cancer predicts metastatic progression

BACKGROUND

The majority of prostate cancers (CaP) are detected in early stages with uncertain prognosis. Therefore, an intensive effort is underway to define early predictive markers of CaP with aggressive progression characteristics.

METHODS

In order to define such prognostic markers, we performed comparative analyses of transcriptomes of well- and poorly differentiated (PD) tumor cells from primary tumors of patients (N=40) with 78 months of mean follow-up after radical prostatectomy. Validation experiments were carried out at transcript level by quantitative real-time reverse transcriptase-PCR (RT-PCR) (N=110) and at protein level by immunohistochemistry (N=53) in primary tumors from an independent patient cohort.

RESULTS

Association of a biochemical network of 12 genes with SPARC gene as a central node was highlighted with PD phenotype. Of note, there was remarkable enrichment of NKXH_NKXH_HOX composite regulatory elements in the promoter of the genes in this network suggesting a biological significance of this gene-expression regulatory mechanism in CaP progression. Further, quantitative expression analyses of SPARC mRNA in primary prostate tumor cells of 110 patients validated the association of SPARC expression with poor differentiation and higher Gleason score. Most significantly, higher SPARC protein expression at the time of prostatectomy was associated with the subsequent development of metastasis (P=0.0006, AUC=0.803).

CONCLUSIONS

In summary, we propose that evaluation of SPARC in primary CaP has potential as a prognostic marker of metastatic progression.

Overexpression of C-MYC oncogene in prostate cancer predicts biochemical recurrence

Alterations of chromosome 8, including amplification at 8q24 harboring the C-MYC oncogene, have been noted as one of the most common chromosomal abnormalities in prostate cancer (CaP) progression. However, the frequency of C-MYC alterations in CaP has remained uncertain. A recent study, using a new anti-MYC antibody, described prevalent upregulation of nuclear C-MYC protein expression as an early oncogenic alteration in CaP. Further, we have recently reported regulation of C-MYC expression by ERG and a significant correlation between C-MYC overexpression and TMPRSS2-ERG fusion in early stage CaP. These emerging data suggest that increased C-MYC expression may be a critical and early oncogenic event driving CaP progression. In this study, we assessed whether C-MYC mRNA overexpression in primary prostate tumors was predictive of more aggressive tumor or disease progression. Our approach was to quantitatively determine C-MYC mRNA expression levels in laser capture micro-dissected tumor cells and matched benign epithelial cells in a radical prostatectomy cohort with long follow-up data available. On the basis of our results, we conclude that elevated C-MYC expression in primary prostate tumor is biologically relevant and may be a predictor of future biochemical recurrence.