A role for RIO kinases in the crosshair of cancer research and therapy

RIO (right open reading frame) family of kinases including RIOK1, RIOK2 and RIOK3 are known for their role in the ribosomal biogenesis. Dysfunction of RIO kinases have been implicated in malignancies, including acute myeloid leukemia, glioma, breast, colorectal, lung and prostatic adenocarcinoma suggesting RIO kinases as potential targets in cancer. In vitro, in vivo and clinical studies have demonstrated that RIO kinases are overexpressed in various types of cancers suggesting important roles in tumorigenesis, especially in metastasis. In the context of malignancies, RIO kinases are involved in cancer-promoting pathways including AKT/mTOR, RAS, p53 and NF-κB and cell cycle regulation. Here we review the role of RIO kinases in cancer development emphasizing their potential as therapeutic target and encouraging further development and investigation of inhibitors in the context of cancer.

Increased frequency of CHD1 deletions in prostate cancers of African American men is associated with rapid disease progression without inducing homologous recombination deficiency

We analyzed genomic data derived from the prostate cancer of African and European American men in order to identify differences that may contribute to racial disparity of outcome and that could also define novel therapeutic strategies. In addition to analyzing patient derived next generation sequencing data, we performed FISH based confirmatory studies of Chromodomain helicase DNA-binding protein 1 ( CHD1 ) loss on prostate cancer tissue microarrays. We created CRISPR edited, CHD1 deficient prostate cancer cell lines for genomic, drug sensitivity and functional homologous recombination (HR) activity analysis. We found that subclonal deletion of CHD1 is nearly three times as frequent in prostate tumors of African American men than in men of European ancestry and it associates with rapid disease progression. We further showed that CHD1 deletion is not associated with homologous recombination deficiency associated mutational signatures in prostate cancer. In prostate cancer cell line models CHD1 deletion did not induce HR deficiency as detected by RAD51 foci formation assay or mutational signatures, which was consistent with the moderate increase of olaparib sensitivity. CHD1 deficient prostate cancer cells, however, showed higher sensitivity to talazoparib. CHD1 loss may contribute to worse outcome of prostate cancer in African American men. A deeper understanding of the interaction between CHD1 loss and PARP inhibitor sensitivity will be needed to determine the optimal use of targeted agents such as talazoparib in the context of castration resistant prostate cancer.

Filamin A Is a Prognostic Serum Biomarker for Differentiating Benign Prostatic Hyperplasia from Prostate Cancer in Caucasian and African American Men

Prostate cancer represents a significant health risk to aging men, in which diagnostic challenges to the identification of aggressive cancers remain unmet. Prostate cancer screening is driven by the prostate-specific antigen (PSA); however, in men with benign prostatic hyperplasia (BPH) due to an enlarged prostate and elevated PSA, PSA's screening utility is diminished, resulting in many unnecessary biopsies. To address this issue, we previously identified a cleaved fragment of Filamin A (FLNA) protein (as measured with IP-MRM mass spectrometry assessment as a prognostic biomarker for stratifying BPH from prostate cancer and subsequently evaluated its expanded utility in Caucasian (CA) and African American (AA) men. All men had a negative digital rectal examination (DRE) and PSA between 4 and 10 ng/mL and underwent prostate biopsy. In AA men, FLNA serum levels exhibited diagnostic utility for stratifying BPH from patients with aggressive prostate cancer (0.71 AUC and 12.2 OR in 48 men with BPH and 60 men with PCa) and outperformed PSA (0.50 AUC, 2.2 OR). In CA men, FLNA serum levels also exhibited diagnostic utility for stratifying BPH from patients with aggressive prostate cancer (0.74 AUC and 19.4 OR in 191 men with BPH and 109 men with PCa) and outperformed PSA (0.46 AUC, 0.32 OR). Herein, we established FLNA alone as a serum biomarker for stratifying men with BPH vs. those with high Gleason (7-10) prostate cancers compared to the current diagnostic paradigm of using PSA. This approach demonstrates clinical actionability of FLNA alone without the requirement of prostate volume measurement as a test with utility in AA and CA men and represents a significant opportunity to decrease the number of unnecessary biopsies in aggressive prostate cancer diagnoses.

Germline Mutations and Ancestry in Prostate Cancer

PURPOSE OF REVIEW

Prostate cancer is the most frequently diagnosed non-cutaneous malignancy of men in the USA; notably, the incidence is higher among men of African, followed by European and Asian ancestry. Germline mutations and, in particular, mutations in DNA damage repair genes (DDRGs) have been implicated in the pathogenesis of prostate cancer. This review intends to discuss the implication of ancestry on prostate cancer, specifically in regard to lack of diversity in genomic and genetic databases and the ability of providers to properly counsel patients on the significance of cancer genetic results.

RECENT FINDINGS

Ancestral differences in prostate cancer-associated DDRG germline mutations are increasingly recognized. Guidelines for treatment by the National Comprehensive Cancer Network® (NCCN®) support germline testing in certain patients, and a myriad of genetic testing panels for DDRG mutations are now available in clinical practice. However, the consensus among providers on what genes and mutations to include in the genetic tests has evolved from experience from men of European ancestry (EA). Gaps in ancestry-informed clinical practice exist in genetic risk assessment, implementation of screening, counseling, guiding recommendations, treatment, and clinical trial enrollment. The lack of diversity in tumor genomic and genetic databases may hinder ancestry-specific disease-predisposing alterations from being discovered and targeted in prostate cancer and, therefore, impede the ability of providers to accurately counsel patients on the significance of cancer genetic test results.

Hematological Toxicities with PARP Inhibitors in Prostate Cancer: A Systematic Review and Meta-Analysis of Phase II/III Randomized Controlled Trials

BACKGROUND

Poly ADP-ribose polymerase inhibitors (PARPis) are an important class of therapeutics for metastatic castration-resistant prostate cancer (mCRPC). Unlike hormone-based treatments for mCRPC, PARPis are not without drug-related hematological adverse events.

OBJECTIVE

To review the evidence on hematological toxicities, including anemia, thrombocytopenia, and neutropenia from PARPis in prostate cancer.

STUDY METHODOLOGY

A systematic review and meta-analysis using the PRISMA guidelines was performed for phase II and III randomized controlled trials (RCTs) of PARPis in prostate cancer. PubMed, Embase, and Ovid All EBM reviews-Cochrane were queried from inception to 9 June 2023. The Mantel-Haenszel method was used to report risk ratios (RR) and 95% confidence intervals (CI) for all-grade and high-grade anemia, thrombocytopenia, and neutropenia toxicities.

RESULTS

The systematic review retrieved eight phase II and III RCTs; specifically, eight were included in the anemia, five in the all-grade thrombocytopenia and neutropenia, and four in the high-grade thrombocytopenia and neutropenia outcomes. Compared to a placebo and/or other non-PARPi treatments, PARPi use was associated with an increased risk of all-grade anemia (RR, 3.37; 95% CI, 2.37-4.79; p < 0.00001), thrombocytopenia (RR, 4.54; 95% CI, 1.97-10.44; p = 0.0004), and neutropenia (RR, 3.11; 95% CI, 1.60-6.03; p = 0.0008). High-grade anemia (RR, 6.94; 95% CI, 4.06-11.86; p < 0.00001) and thrombocytopenia (RR, 5.52; 95% CI, 2.80-10.88; p < 0.00001) were also associated with an increased risk, while high-grade neutropenia (RR, 3.63; 95% CI, 0.77-17.23; p = 0.10) showed no significant association. Subgroup stratification analyses showed differences in various all-grade and high-grade toxicities.

CONCLUSION

PARPis were associated with an increased risk of hematological AEs. Future studies with more pooled RCTs will enhance this understanding and continue to inform patient-physician shared decision-making. Future studies may also have a role in improving the current management strategies for these AEs.

First Dark Matter Search Results from the LUX-ZEPLIN (LZ) Experiment

The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This Letter reports results from LUX-ZEPLIN's first search for weakly interacting massive particles (WIMPs) with an exposure of 60 live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9  GeV/c^{2}. The most stringent limit is set for spin-independent scattering at 36  GeV/c^{2}, rejecting cross sections above 9.2×10^{-48}  cm at the 90% confidence level.

Development and characterization of an ETV1 rabbit monoclonal antibody for the immunohistochemical detection of ETV1 expression in cancer tissue specimens

BACKGROUND

Aberrant ETV1 overexpression arising from gene rearrangements or mutations occur frequently in prostate cancer, round cell sarcomas, gastrointestinal stromal tumors, gliomas, and other malignancies. The absence of specific monoclonal antibodies (mAb) has limited its detection and our understanding of its oncogenic function.

METHODS

An ETV1 specific rabbit mAb (29E4) was raised using an immunogenic peptide. Key residues essential for its binding were probed by ELISA and its binding kinetics were measured by surface plasmon resonance imaging (SPRi). Its selective binding to ETV1 was assessed by immunoblots and immunofluorescence assays (IFA), and by both single and double-immuno-histochemistry (IHC) assays on prostate cancer tissue specimens.

RESULTS

Immunoblot results showed that the mAb is highly specific and lacked cross-reactivity with other ETS factors. A minimal epitope with two phenylalanine residues at its core was found to be required for effective mAb binding. SPRi measurements revealed an equilibrium dissociation constant in the picomolar range, confirming its high affinity. ETV1 (+) tumors were detected in prostate cancer tissue microarray cases evaluated. IHC staining of whole-mounted sections revealed glands with a mosaic staining pattern of cells that are partly ETV1 (+) and interspersed with ETV1 (-) cells. Duplex IHC, using ETV1 and ERG mAbs, detected collision tumors containing glands with distinct ETV1 (+) and ERG (+) cells.

CONCLUSIONS

The selective detection of ETV1 by the 29E4 mAb in immunoblots, IFA, and IHC assays using human prostate tissue specimens reveals a potential utility for the diagnosis, the prognosis of prostate adenocarcinoma and other cancers, and the stratification of patients for treatment by ETV1 inhibitors.

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.

Emerging Developments in ETS-Positive Prostate Cancer Therapy

Prostate cancer is a global health concern, which has a low survival rate in its advanced stages. Even though second-generation androgen receptor-axis inhibitors serve as the mainstay treatment options, utmost of the metastatic cases progress into castration-resistant prostate cancer after their initial treatment response with poor prognostic outcomes. Hence, there is a dire need to develop effective inhibitors that aim the causal oncogenes tangled in the prostate cancer initiation and progression. Molecular-targeted therapy against E-26 transformation-specific (ETS) transcription factors, particularly ETS-related gene, has gained wide attention as a potential treatment strategy. ETS rearrangements with the male hormone responsive transmembrane protease serine 2 promoter defines a significant number of prostate cancer cases and is responsible for cancer initiation and progression. Notably, inhibition of ETS activity has shown to reduce tumorigenesis, thus highlighting its potential as a clinical therapeutic target. In this review, we recapitulate the various targeted drug approaches, including small molecules, peptidomimetics, nucleic acids, and many others, aimed to suppress ETS activity. Several inhibitors have demonstrated ERG antagonist activity in prostate cancer, but further investigations into their molecular mechanisms and impacts on nontumor ETS-containing tissues is warranted.

Abstract 2220: Immunohistochemical detection of prostate cancer heterogeneity by using ETS and PTEN monoclonal antibodies

The multifocality and highly variable molecular pathology of prostate cancer are underlying features of this clinically heterogeneous disease. Most patients harbor multiple molecularly distinct cancer foci at diagnosis that likely arose as independent clones. There is a critical need for molecular biomarkers that can distinguish the multifocality and inter-focal heterogeneity of tumors and help stratify patients for treatment. PTEN loss and ETS gene rearrangements are among the most prevalent genomic alterations in prostate carcinogenesis. The detection of both ERG overexpression and PTEN protein loss by immunohistochemistry (IHC) have proven to be reliable substitutes for detecting genomic alterations by fluorescence in situ hybridization (FISH) assay. We developed monoclonal antibodies against ETV1 and ETV4 and evaluated their performance in prostate cancer specimens. The expression of ETV1, ETV4, were examined in relation to ERG and loss of PTEN expression in TMAs constructed from primary prostate cancer specimens of two independent patient cohorts. The first TMA was constructed from multiple 1 mm cores representing distinct tumor focus from multifocal tumors from 50 African American (AA) and 50 Caucasian American (CA) men. The second was constructed from a single 2 mm core of individual tumors from an independent cohort of 152 AA and 304 CA men. We present results on the expression of each protein biomarker in the context of patient race and their association with clinico-pathologic features, together with concurrence or mutual exclusiveness for each event. These results support the application of ETS monoclonal antibodies in IHC assays to detect prostate cancer tumor heterogeneity and to identify subsets of prostate cancer.

Citation Format: Cara Schafer, Denise Young, Yingjie Song, Jiji Jiang, Albert Dobi, Gyorgy Petrovics, Bettina F. Drake, Gregory T. Chesnut, Isabell A. Sesterhenn, Shyh-Han Tan. Immunohistochemical detection of prostate cancer heterogeneity by using ETS and PTEN monoclonal antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2220.

Focal p53 protein expression and lymphovascular invasion in primary prostate tumors predict metastatic progression

TP53 is one of the most frequently altered genes in prostate cancer. The precise assessment of its focal alterations in primary tumors by immunohistochemistry (IHC) has significantly enhanced its prognosis. p53 protein expression and lymphovascular invasion (LVI) were evaluated for predicting metastatic progression by IHC staining of representative whole-mounted prostate sections from a cohort of 189 radical prostatectomy patients with up to 20 years of clinical follow-up. Kaplan–Meier survival curves were used to examine time to distant metastasis (DM) as a function of p53 expression and LVI status. TP53 targeted sequencing was performed in ten tumors with the highest expression of p53 staining. Nearly half (49.8%) of prostate tumors examined showed focal p53 expression while 26.6% showed evidence of LVI. p53(+) tumors had higher pathologic T stage, Grade Group, Nuclear Grade, and more frequent LVI. p53 expression of > 5% and LVI, individually and jointly, are associated with poorer DM-free survival. TP53 mutations were detected in seven of ten tumors sequenced. Four tumors with the highest p53 expression harbored likely pathogenic or pathogenic mutations. High levels of p53 expression suggest the likelihood of pathogenic TP53 alterations and, together with LVI status, could enhance early prognostication of prostate cancer progression.

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.

New Selective Inhibitors of ERG Positive Prostate Cancer: ERGi-USU-6 Salt Derivatives

Prostate cancer is among the leading causes of cancer related death of men in the United States. The ERG gene fusion leading to overexpression of near full-length ERG transcript and protein represents most prevalent (50–65%) prostate cancer driver gene alterations. The ERG oncoprotein overexpression persists in approximately 35% of metastatic castration resistant prostate cancers. Due to the emergence of eventual refractoriness to second- and third-generation androgen axis-based inhibitors, there remains a pressing need to develop drugs targeting other validated prostate cancer drivers such as ERG. Here we report the new and more potent ERG inhibitor ERGi-USU-6 developed by structure–activity studies from the parental ERGi-USU. We have developed an improved procedure for the synthesis of ERGi-USU-6 and identified a salt formulation that further improves its activity in biological assays for selective targeting of ERG harboring prostate cancer cells.

Abstract 1248: ERGi-USU-6 salt derivatives, a selective inhibitor for ERG positive prostate cancer cells

Background: Approximately half of prostate cancer patients harbor the oncogenic TMPRSS2-ERG gene fusion expressing the ERG oncoprotein. Our lead compound, ERGi-USU, is a potent small molecule inhibitor that binds the atypical kinase RIOK2 leading to the inhibition of the growth of ERG positive cancer cells reducing ERG levels. We have developed a new and more effective derivative, ERGi-USU-6. We have reported the new salts formula EB3P0-16 of ERGi-USU-6 inhibiting the growth of ERG positive prostate cancer cells at IC50=89nM achieving the range of FDA approved drugs. Encouraged by this success we have designed and tested a broad array of new salt formulations to further improve the biological activity of ERGi-USU-6.

Methods: From fifty potential salt formulations, we prioritized candidate salts based on the structure, solubility, ionic hydrophobic/hydrophilic characteristics. Series of salts were synthesized by chemical reactions with ERGI-USU-6. Selected formulas include, bisulfate, butyrate, carbonate, salicylate, tartrate salts. The different stages of salt formulation included the testing of a) preformulation, b) pre-formulation processing, c) physicochemical properties, d) solubility, e) pKa, f) partition coefficient, g) pH- solubility profiling, h) prodrug formulation, and i) polymorphism. The IC50 values for ERG protein inhibition was compared to the parental compound and were calculated in a 12-step dilution range and were repeated thrice. The protein levels were quantified by measuring protein levels in a wide range using iBright instrument.

Results: A total of 21 salt formulas were prioritized and synthesized. The result confirmed the lead characteristics of EB3P0-16. However, among the new formulas four other salt derivatives showed improved ERG protein inhibition compared to the parental compound. Also, we gained new insights in designing the next generation of formula by the exclusion of chemical structures that did not lead to improvement.

Conclusion: This study confirmed EB3P0-16 as the lead formula of ERGi-USU-6. We found four new salt formulas with improved activity achieving ERG protein inhibition within the effective concentration range. The significance of our findings opens the possibility of new deigns towards the pre-clinical testing of ERG inhibitors.

Disclaimer: The opinions or assertions contained herein are the private ones of the author/speaker and are not to be construed as official or reflecting the views of the Department of Defense, the Uniformed Services University of the Health Sciences or any other agency of the U.S. Government. The identification of specific products, scientific instrumentation, or organization is considered an integral part of the scientific endeavor and does not constitute endorsement or implied endorsement on the part of the author, DoD, or any component agency.

Citation Format: Binil Eldhose, Charles P. Xavier, Mallesh Pandrala, Albert Dobi, Sanjay V. Malhotra. ERGi-USU-6 salt derivatives, a selective inhibitor for ERG positive prostate cancer cells [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 1248.

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 2565: Detection of ETV1 expression in human prostate tissue specimens using a novel and highly specific rabbit monoclonal antibody

Introduction: ETV1 is frequently involved in genomic fusions and translocation events that lead to its overexpression in multiple cancers. These events occur in approximately 5% of prostate cancers, which are mutually exclusive from tumors harboring TMPRSS2-ERG fusion or PTEN deletion. Studies suggest a correlation between strong ETV1 protein expression and poor outcome in prostate cancer. ETV1 has been reported to synergistically cooperate with KIT as a lineage survival factor in gastrointestinal stromal tumors. The expression of ETV1 in a subset of sarcomas that harbor CICrearrangements or CIC-DUX4 gene fusions presents a reliable molecular signature for the diagnosis of this cancer. Our understanding of the role that ETV1 plays in the activation of prostate cancer has been limited by the lack of ETV1 specific antibodies.

Methods: A novel ETV1 monoclonal antibody (MAb) was raised by immunization of ETV1 peptides in rabbit followed by screening of hybridomas by ELISA and immunoblot assays. Further screening using exogenously expressed ETV1, ETV4, ETV5, ERG, SPDEF, and FLI1 proteins identified the clone with the most reactive MAb. Purified MAb was used to evaluate ETV1 expression on a tissue micro-array (TMA) constructed from radical prostatectomies of 50 African American (AA) and 50 Caucasian American (CA) patients by immunohistochemistry (IHC). Key residues required for Mab binding were mapped by ELISA using overlapping peptides and alanine scanning.

Results: IHC evaluation using the ETV1 specific rabbit Mab on a prostate cancer TMA derived from 100 patients identified five ETV1 positive cases, of whom four were CA. The index tumors for these five ETV1 cases were ERG negative. One patient harbored both ERG positive and ERG negative tumor foci, and as expected, the ETV1 positive tumor focus was ERG negative, and vice versa.

Conclusions: We developed a novel rabbit monoclonal ETV1 antibody that is suitable for IHC assay in human prostate tissue. An evaluation of prostate cancer specimens confirmed the reported frequency of ETV1 alteration. Further evaluation using tissue specimens from larger cohorts to establish the sensitivity and specificity of this antibody and validate the utility of ETV1 detection in improving the diagnosis and stratification of prostate and other cancers are in progress.

Citation Format: Shyh-Han Tan, Denise Young, Sally Elsamanoudi, Jacob Kagan, Sudhir Srivastava, Albert Dobi, Gyorgy Petrovics, Isabell A. Sesterhenn, Gregory T. Chesnut. Detection of ETV1 expression in human prostate tissue specimens using a novel and highly specific rabbit monoclonal antibody [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 2565.

Abstract 2526: PMEPA1 gene isoforms indicated aggressive disease progression in non-prostate solid tumors

Introduction: Abnormal activation of androgen and TGF-β signaling play important roles in tumorigenesis of various solid tumors including prostate, lung and colon cancers. As an androgen and TGF-β responsive gene, PMEPA1 has been defined to regulate androgen and TGF-β signaling via negative feed-back loops. Our lab recently established that PMEPA1 distinct isoforms (isoforms a, b, c, d and e) with disparities within N-terminus protein sequences navigated different regulations of androgen/TGF-β signaling. In this study, the expressions and the correlations to disease progression of PMEPA1 isoforms were investigated in prostate, breast, lung and colon cancers.

Methods: RNA seq data from total 2479 solid tumor samples in the TCGA dataset were used to study the correlation between expressions of PMEPA1 isoforms and disease progression including Gleason score, pathology stages, progression free survival rate (PFS) and overall survival rate (OS). The cohort is composed of 482 prostate, 1049 breast, 499 lung and 449 colon cancer patients.

Results: In prostate cancer, TCGA data analysis showed that lower transcript level of PMEPA1-b isoform associated with higher Gleason scores and lower progression free survival rate (PFS) (P=0.014) and worse overall survival rate (OS) (P&lt;0.01). The ratio of mRNA levels of PMEPA1-a versus PMEPA-b indicated higher Gleason score, lower PFS rate (P=0.0063) and worse OS rate (P=0.0042). In contrast, higher expression of both PMEPA1-a and PMEPA1-b associated with lower PFS (P=0.023 and 0.028, respectively) in breast cancer. And the enhanced ratio of PMEPA1-a/b was also found to indicate lower PFS (P=0.016) and worse OS (P=0.016) in breast cancer. Similarly, the increased transcript levels of PMEPA1-a and PMEPA1-b isoforms significantly associated with lower PFS and worse OS rates in lung and colon cancer. The expressions of PMEPA1 isoforms were not found to associate with pathology stages of non-prostate tumors. Interestingly, our data further showed that the expressions of both PMEPA1-a and PMEPA1-b isoforms were positively correlated to TGF-β responsive genes including COL1A and THBS1 in breast cancer, lung adenocarcinoma, lung square cancer and colon cancers, which may indicate non-androgen regulation mechanism of PMEPA1-b isoform in non-prostate context.

Conclusions: Our data establish the biomarker potential of PMEPA1 isoforms (a and b) indicating more aggressive disease progressions in 4 solid tumors, further underscoring the PMEPA1 isoform specific biological functions to differentiate regulation of androgen and TGF-β signaling in various organ specific contexts.

Citation Format: Shashwat Sharad, Zsófia M. Sztupinszki, Zoltan Szallasi, Shiv Srivastava, Alagarsamy Srinivasan, Albert Dobi, Hua Li. PMEPA1 gene isoforms indicated aggressive disease progression in non-prostate solid tumors [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 2526.

Philadelphia Prostate Cancer Genetic Consensus Conference 2019 and implications for military medicine

INTRODUCTION The objective of our review is to summarize the 2019 Philadelphia Prostate Cancer Genetic Consensus recommendations and discuss their implications to the US Military Health System.

MATERIALS AND METHODS

Literature review.

RESULTS

Our fighting force and retired service members will significantly benefit from the Philadelphia Prostate Cancer Genetic Consensus recommendations. Moreover, the experience of the equal access US Military Health System may help advancing genetic testing for cancer at national levels.

CONCLUSIONS

Priorities recommended by the 2019 Consensus for more research on genetic predisposition to prostate cancer in racially diverse populations is a promising step. The US Military Health System has the ability of providing equal access to implement advanced germline testing for its racially diverse population.

Prognostic Features of Biochemical Recurrence of Prostate Cancer Following Radical Prostatectomy Based on Multiparametric MRI and Immunohistochemistry Analysis of MRI-guided Biopsy Specimens

Background Although prostate MRI is routinely used for the detection and staging of localized prostate cancer, imaging-based assessment and targeted molecular sampling for risk stratification are an active area of research. Purpose To evaluate features of preoperative MRI and MRI-guided biopsy immunohistochemistry (IHC) findings associated with biochemical recurrence (BCR) of prostate cancer after surgery. Materials and Methods In this retrospective case-control study, patients underwent multiparametric MRI before MRI-guided biopsy followed by radical prostatectomy between 2008 and 2016. Lesions were retrospectively scored with the Prostate Imaging Reporting and Data System (PI-RADS) (version 2) by radiologists who were blinded to the clinical-pathologic results. The IHC staining, including stains for the ETS-related gene, phosphatase and tensin homolog, androgen receptor, prostate specific antigen, and p53, was performed with targeted biopsy specimens of the index lesion (highest suspicion at MRI and pathologic grade) and scored by pathologists who were blinded to clinical-pathologic outcomes. Cox proportional hazards regression analysis was used to evaluate associations with recurrence-free survival (RFS). Results The median RFS was 31.7 months (range, 1-101 months) for 39 patients (median age, 62 years; age range, 47-76 years) without BCR and 14.6 months (range, 1-61 months) for 40 patients (median age, 59 years; age range, 47-73 years) with BCR. MRI features that showed a significant relationship with the RFS interval included an index lesion with a PI-RADS score of 5 (hazard ratio [HR], 2.10; 95% CI: 1.05, 4.21; P = .04); index lesion burden, defined as ratio of index lesion volume to prostate volume (HR, 1.55; 95% CI: 1.2, 2.1; P = .003); and suspicion of extraprostatic extension (EPE) (HR, 2.18; 95% CI: 1.1, 4.2; P = .02). Presurgical multivariable analysis indicated that suspicion of EPE at MRI (adjusted HR, 2.19; 95% CI: 1.1, 4.3; P = .02) and p53 stain intensity (adjusted HR, 2.22; 95% CI: 1.0, 4.7; P = .04) were significantly associated with RFS. Conclusion MRI features, including Prostate Imaging Reporting and Data System score, index lesion burden, extraprostatic extension, and preoperative guided biopsy p53 immunohistochemistry stain intensity are associated with biochemical relapse of prostate cancer after surgery. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Costa in this issue.

Age and Tumor Differentiation-Associated Gene Expression Based Analysis of Non-Familial Prostate Cancers

Prostate cancer incidence in young men has increased. Patients diagnosed at an earlier age are likely to have aggressive prostate cancer and treatment decisions are continuing to be weighted by patient age and life expectancy. Identification of age-associated gene-expression signatures hold great potential to augment current and future treatment modalities. To investigate age-specific tumor associated gene signatures and their potential biomarkers for disease aggressiveness, this study was designed and stratified into well and poorly differentiated tumor types of young (42–58 years) and old (66–73 years) prostate cancer patients. The differentially expressed genes related to tumor-normal differences between non-familial prostate cancer patients were identified and several genes uniquely associated with the age and tumor differentiation are markedly polarized. Overexpressed genes known to be associated with somatic genomic alterations was predominantly found in young men, such as TMPRESS2-ERG and c-MYC. On the other hand, old men have mostly down-regulated gene expressions indicating the loss of protective genes and reduced cell mediated immunity indicated by decreased HLA-A and HLA-B expression. The normalization for the benign signatures between the age groups indicates a significant age and tumor dependent heterogeneity exists among the patients with a great potential for age-specific and tumor differentiation-based therapeutic stratification of prostate cancer.

Abstract IA15: Development of Novel Models and Identification of Therapeutic Vulnerabilities in Highly Aggressive Prostate Cancer In African American Men

African Americans have the highest mortality rate and shortest survival of any racial/ethnic group in the US for most cancers. An estimated 29,570 cases of prostate cancer are expected to be diagnosed in AA men in 2020. The average annual incidence rate for African American men is 76% higher than the rate in Caucasian Americans. Prostate cancer is the second leading cause of cancer death in African American men, with an estimated 5,350 deaths expected in 2020, which is the highest of all ethnic groups (2.2X higher than Caucasian men). These disparities are appalling and demand immediate action. While the underlying causes are multifactorial, recent studies demonstrate that African American men are at higher risk of being diagnosed with prostate cancer, have higher Gleason grades, and increased risk of progression after radical prostatectomy (RP), even in equal access settings and after accounting for socioeconomic status. These data strongly argue that there is a significant underlying biological/genetic difference between African Americans and Caucasian American men with prostate cancer. Importantly, they highlight an unmet need in order to deliver personalized therapeutic options and ultimately, improve clinical outcomes. Unfortunately, most preclinical studies are performed in prostate cancer cell lines and patient-derived xenografts (PDXs) isolated from patients of Caucasian origin. At Baylor College of Medicine, we are leveraging the high numbers of minority cancer patients in our GU clinics, to generate and utilize innovative prostate cancer PDX and organoid models of diverse racial/ethnic minority origin, which will broaden our understanding of the molecular basis of the disease as well as expedite the drug discovery process. We will discuss preliminary findings from our ongoing studies in genomic and transcriptomic profiling of African American patients, progress in our development of novel prostate cancer models, and lastly, emerging therapeutic opportunities based on precision oncology.

Citation Format: Salma Kaochar, Patricia Castro, Sandra Grimm, Darlene Skapura, Matthew Rodriguez, Maurice Dufilho, Cammy Mason, Maria Machado Heredia, Quentxia Wrighting, Jami Daly, Matthew Robertson, Nora Navone, Jacob Berchuck, Matthew Freeman, Zoltan Szallasi, Albert Dobi, Guiherme Godoy, Michael Scheurer, Heidi Dowst, Susan Hilsenbeck, Martha Mims, Anita Sabichi, Edward Yen, Cristian Coarfa, Michael Ittmann, Nicholas Mitsiades. Development of Novel Models and Identification of Therapeutic Vulnerabilities in Highly Aggressive Prostate Cancer In African American Men [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr IA15.

Prognostic features of Annexin A2 expression in prostate cancer

ANXA2 (Annexin A2 or Annexin II) is a calcium dependent phospholipid binding protein with diverse cellular functions. While ANXA2 is either absent or expressed focally in the prostate epithelium of well and moderately differentiated tumours, it is highly expressed in a subset of poorly differentiated tumours. Here we examined the association between ANXA2 expression and tumour progression, with consideration of ERG expression status and patient race (Caucasian American and African American). We evaluated ANXA2 and ERG expression in index tumours by immunohistochemistry of whole mounted prostate sections and tissue microarrays derived from radical prostatectomies of 176 patients, matched for long term post-radical prostatectomy follow-up of up to 22 years (median 12.6 years), race and pathological stage. Expression of ERG and ANXA2 was analysed for correlation with grade group (GG), and pathological T (pT) stage. Kaplan-Meier estimation curves were used to examine associations between ANXA2 or ERG expression and biochemical recurrence (BCR) free survival, and distant metastasis free survival. Significant associations were found between ANXA2(+) index tumours and poorest grade groups (GG 4-5, p=0.0037), and worse pathological stage (pT 3-4, p=0.0142). Patients with ANXA2(+) prostate tumours showed trends towards earlier BCR and metastatic progression. ANXA2(+)/ERG(-) tumours were found to be associated with GG 4-5; ANXA2(-)/ERG(+) tumours, with GG 1-2 (p=0.0036). ANXA2 expression was not associated with patient race. The association between high ANXA2 expression and prostate tumours of higher grade (GG 4-5) and stage (pT 3-4) suggests a potential use for ANXA2 as a prognostic biomarker of aggressive prostate cancer.

PMEPA1 Gene Isoforms: A Potential Biomarker and Therapeutic Target in Prostate Cancer

The identification of prostate transmembrane protein androgen induced 1 (PMEPA1), an androgen responsive gene, came initially from the studies of androgen regulatory gene networks in prostate cancer. It was soon followed by the documentation of the expression and functional analysis of transmembrane prostate androgen-induced protein (TMEPAI)/PMEPA1 in other solid tumors including renal, colon, breast, lung, and ovarian cancers. Further elucidation of PMEPA1 gene expression and sequence analysis revealed the presence of five isoforms with distinct extracellular domains (isoforms a, b, c, d, and e). Notably, the predicted amino acid sequences of PMEPA1 isoforms show differences at the N-termini, a conserved membrane spanning and cytoplasmic domains. PMEPA1 serves as an essential regulator of multiple signaling pathways including androgen and TGF-β signaling in solid tumors. Structure-function studies indicate that specific motifs present in the cytoplasmic domain (PY, SIM, SH3, and WW binding domains) are utilized to mediate isoform-specific functions through interactions with other proteins. The understanding of the “division of labor” paradigm exhibited by PMEPA1 isoforms further expands our knowledge of gene’s multiple functions in tumorigenesis. In this review, we aim to summarize the most recent advances in understanding of PMEPA1 isoform-specific functions and their associations with prostate cancer progression, highlighting the potentials as biomarker and therapeutic target in prostate cancer.

Implementation of Germline Testing for Prostate Cancer: Philadelphia Prostate Cancer Consensus Conference 2019

PURPOSE

Germline testing (GT) is a central feature of prostate cancer (PCA) treatment, management, and hereditary cancer assessment. Critical needs include optimized multigene testing strategies that incorporate evolving genetic data, consistency in GT indications and management, and alternate genetic evaluation models that address the rising demand for genetic services.

METHODS

A multidisciplinary consensus conference that included experts, stakeholders, and national organization leaders was convened in response to current practice challenges and to develop a genetic implementation framework. Evidence review informed questions using the modified Delphi model. The final framework included criteria with strong (> 75%) agreement (Recommend) or moderate (50% to 74%) agreement (Consider).

RESULTS

Large germline panels and somatic testing were recommended for metastatic PCA. Reflex testing-initial testing of priority genes followed by expanded testing-was suggested for multiple scenarios. Metastatic disease or family history suggestive of hereditary PCA was recommended for GT. Additional family history and pathologic criteria garnered moderate consensus. Priority genes to test for metastatic disease treatment included BRCA2, BRCA1, and mismatch repair genes, with broader testing, such as ATM, for clinical trial eligibility. BRCA2 was recommended for active surveillance discussions. Screening starting at age 40 years or 10 years before the youngest PCA diagnosis in a family was recommended for BRCA2 carriers, with consideration in HOXB13, BRCA1, ATM, and mismatch repair carriers. Collaborative (point-of-care) evaluation models between health care and genetic providers was endorsed to address the genetic counseling shortage. The genetic evaluation framework included optimal pretest informed consent, post-test discussion, cascade testing, and technology-based approaches.

CONCLUSION

This multidisciplinary, consensus-driven PCA genetic implementation framework provides novel guidance to clinicians and patients tailored to the precision era. Multiple research, education, and policy needs remain of importance.

Abstract 5240: Effective inhibition of TMPRSS2-ERG positive prostate cancer cells by a new formula of ERGi-USU-6

Background: Prostatic adenocarcinoma is among the leading cause of cancer-related deaths among men in the United States. The Erythroblast Transformation-Specific-Related Gene, ERG is dormant in normal prostate epithelium. Due to gene fusions, the ERG oncogene is frequently activated by androgenic signals in prostate cancer. ERG disrupts the normal differentiation, promotes epithelial-mesenchymal transition, migratory and invasive properties of cancer cells. Approximately 35% of metastatic castration-resistant prostate cancers harbor ERG oncogene. Due to the failure of androgen axis directed therapies, there is an urgent need to develop inhibitors to targeting prostate cancer-causing genes, such as ERG. We have identified a potent small-molecule inhibitor ERGi-USU that is remarkably selective for inhibiting the growth of ERG positive cancer cells through direct binding to the RIOK2 atypical kinase, a putative upstream regulator of ERG. We completed a structure-activity relationship (SAR) study and compound development resulting in the potent derivative, ERGi-USU-6. Our current objective is to improve the therapeutic properties of ERGi-USU-6, by new salt formulations.

Methods: Evaluation of the five selected salt formulations of ERGi-USU-6 were performed by assessing the growth of ERG positive prostate cancer cell line (VCaP) and by monitoring ERG and RIOK2 protein levels. Selectivity was assessed by monitoring the growth, endogenous ERG and RIOK2 levels in normal ERG positive human umbilical vein derived endothelial cells (HUVEC). The IC50 values for cell growth, compared to the parental compound were calculated in a 12-step dilution range performed in triplicates and independently repeated three times. Cell growth was measured by quantitative Cell Glow assay monitoring viable cells using Perkin Elmer Envision assay instrument and protein levels were quantified by measuring bioluminescence in IBright instrument in a wide dynamic range.

Results: One new salt formula with improved activity were identified, demonstrating improved cell growth (IC50=89nM vs. parental IC50=139), ERG protein and RIOK2 protein inhibition. None of the salt formulas of ERGi-USU-6 showed any effect on the primary cultures of the ERG positive normal endothelial cells (HUVEC) in the effective concentration range.

Conclusion: The first evaluation of salt formulas of ERGi-USU-6 may open the possibilities for preclinical assessments of this remarkably cancer-selective compound.

Citation Format: Binil Eldhose, Charles P. Xavier, Mallesh Pandrala, Sanjay V. Malhotra, Albert Dobi. Effective inhibition of TMPRSS2-ERG positive prostate cancer cells by a new formula of ERGi-USU-6 [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5240.

Proteomic Tissue-Based Classifier for Early Prediction of Prostate Cancer Progression

Although ~40% of screen-detected prostate cancers (PCa) are indolent, advanced-stage PCa is a lethal disease with 5-year survival rates around 29%. Identification of biomarkers for early detection of aggressive disease is a key challenge. Starting with 52 candidate biomarkers, selected from existing PCa genomics datasets and known PCa driver genes, we used targeted mass spectrometry to quantify proteins that significantly differed in primary tumors from PCa patients treated with radical prostatectomy (RP) across three study outcomes: (i) metastasis ≥1-year post-RP, (ii) biochemical recurrence ≥1-year post-RP, and (iii) no progression after ≥10 years post-RP. Sixteen proteins that differed significantly in an initial set of 105 samples were evaluated in the entire cohort (n = 338). A five-protein classifier which combined FOLH1, KLK3, TGFB1, SPARC, and CAMKK2 with existing clinical and pathological standard of care variables demonstrated significant improvement in predicting distant metastasis, achieving an area under the receiver-operating characteristic curve of 0.92 (0.86, 0.99, p = 0.001) and a negative predictive value of 92% in the training/testing analysis. This classifier has the potential to stratify patients based on risk of aggressive, metastatic PCa that will require early intervention compared to low risk patients who could be managed through active surveillance.

Multi-omic serum biomarkers for prognosis of disease progression in prostate cancer

Background

Predicting the clinical course of prostate cancer is challenging due to the wide biological spectrum of the disease. The objective of our study was to identify prostate cancer prognostic markers in patients ‘sera using a multi-omics discovery platform.

Methods

Pre-surgical serum samples collected from a longitudinal, racially diverse, prostate cancer patient cohort (N = 382) were examined. Linear Regression and Bayesian computational approaches integrated with multi-omics, were used to select markers to predict biochemical recurrence (BCR). BCR-free survival was modeled using unadjusted Kaplan–Meier estimation curves and multivariable Cox proportional hazards analysis, adjusted for key pathologic variables. Receiver operating characteristic (ROC) curve statistics were used to examine the predictive value of markers in discriminating BCR events from non-events. The findings were further validated by creating a training set (N = 267) and testing set (N = 115) from the cohort.

Results

Among 382 patients, 72 (19%) experienced a BCR event in a median follow-up time of 6.9 years. Two proteins—Tenascin C (TNC) and Apolipoprotein A1V (Apo-AIV), one metabolite—1-Methyladenosine (1-MA) and one phospholipid molecular species phosphatidic acid (PA) 18:0-22:0 showed a cumulative predictive performance of AUC = 0.78 [OR (95% CI) = 6.56 (2.98–14.40), P < 0.05], in differentiating patients with and without BCR event. In the validation set all four metabolites consistently reproduced an equivalent performance with high negative predictive value (NPV; > 80%) for BCR. The combination of pTstage and Gleason score with the analytes, further increased the sensitivity [AUC = 0.89, 95% (CI) = 4.45–32.05, P < 0.05], with an increased NPV (0.96) and OR (12.4) for BCR. The panel of markers combined with the pathological parameters demonstrated a more accurate prediction of BCR than the pathological parameters alone in prostate cancer.

Conclusions

In this study, a panel of serum analytes were identified that complemented pathologic patient features in predicting prostate cancer progression. This panel offers a new opportunity to complement current prognostic markers and to monitor the potential impact of primary treatment versus surveillance on patient oncological outcome.

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 3165: Identification of candidate biomarkers for aggressive prostate cancer using targeted proteomics and FFPE tissue samples with outcomes data

Introduction: Although many (~40%) of the screen-detected prostate cancers are indolent (Gleason Score &lt;= 6) and pose minimal risk for progression, advanced stage prostate cancer is a lethal disease with 5-year survival rates around 29%. The challenge is to identify biomarkers for early detection of aggressive disease, when the cancer is still organ confined. Such markers would be also used to better select patients with indolent and low risk cancers for active surveillance.

Material and Methods: To identify a panel of protein markers that could predict prostate cancer progression, we developed ultra-sensitive, high-pressure, high-resolution separations coupled with intelligent selection and multiplexing-selected reaction monitoring (PRISM-SRM) assays for 52 protein markers. Candidate protein markers were identified and selected from existing prostate cancer genomics data sets and validated lists of known prostate cancer drivers. The PRISM-SRM assays used heavy isotope-labeled synthetic peptides as internal standards for quantitative proteomics analysis. Study comprised of a prostate cancer patient cohort with organ confined primary tumors (N=338) presenting following post-surgery features: 53 (15.7%) metastatic progression, 124 (36.7%) biochemical recurrence (BCR), and 161 (47.6%) no progression after more than ten years of follow-up after radical prostatectomy. Index tumor region for each case was scraped from representative 10-m sections of formalin-fixed paraffin embedded (FFPE)-whole-mounted prostatectomy specimens and processed for PRISM-SRM analysis.

Results: Overall, PRISM-SRM analysis of the FFPE tissue samples enabled the detection of 42 (80.8%) out of 52 biomarker candidates; in comparison regular LC-SRM without the front-end chromatographic enrichment could detect only 21 (40.4%) of these candidates at the protein level. Kruskal-Wallis testing was used for statistical evaluation of the PRISM-SRM results and comparison of relative protein levels between the “no progression”, BCR and “metastatic progression” groups. Several prostate differentiation/androgen receptor signaling related proteins (FOLH1, PSA and NCOA) and tumor progression-related proteins (TGFB1, CCND1 and SPRC) had significantly different expression levels between the three groups, and showed initial promise in predicting progression to invasive cancer, BCR and metastasis.

Conclusion: Ultra-sensitive targeted proteomics can be used to select and verify performance of early prognostic markers based on the analysis of prostatectomy specimens. The top performing markers appeared able to predict progression from organ confined cancer to BCR and metastasis.

Citation Format: Yuqian Gao, Yi-Ting Wang, Hui Wang, Denise Young, Jennifer Cullen, Yingjie Song, Yongmei Chen, Athena Schepmoes, Gyorgy Petrovics, Thomas Fillmore, Tujin Shi, Wei-Jun Qian, Richard Smith, Sudhir Srivastava, Jacob Kagan, Albert Dobi, Inger Rosner, Karin Rodland, Isabell Sesterhenn, Shiv Srivastava, Tao Liu. Identification of candidate biomarkers for aggressive prostate cancer using targeted proteomics and FFPE tissue samples with outcomes data [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 3165.

Abstract 2772: Recurrent alterations of the TenascinC in highly aggressive neuroendocrine sub-type of prostate cancer

Introduction: Early detection and prognosis of prostate cancer (CaP) is challenging due to its wide spectrum of biological features. Multi-analytic prognostic marker panels have increased sensitivity than single analytes among the biopsy tests and require advanced bioinformatics platform. We aimed to develop a panel of serum biomarkers using multi-omics approach and further characterized their involvement in prostate cancer progression. In a collaborative study between CPDR, Department of Surgery, USU and Berg Health, serum samples (N=385) were examined by multi-omics (proteomics, lipidomics and metabolomics) and Tenascin C (TNC) was identified as one of the promising markers for disease progression in combination with three other analytes, Apolipoprotein AIV, 1-Methyladenosine and a phosphatidic acid (PA 18:0-22:0). The combination of two clinical features, pathological measurement of T-Stage and Gleason score, along with the four molecular analytes further increased the AUC to 0.89 with a NPV of 0.96 and an odds ratio of 12.4. TNC, an extracellular matrix protein, is poorly studied in prostate cancer, though it is expressed in several cancer tissues such as the breast, lung, colon, and the gastrointestinal tract.

Methods: Publically available prostate cancer databases (cBioportal Version 1.17.1, http://www.cbioportal.org/index.do) were queried for TNC, and known driver oncogenes in prostate cancer, ERG, AR and MYC.

Results: Publically available prostate cancer databases (cBioPortal) demonstrated alterations (either amplifications or mutations) in TNC in 10 out of 16 datasets. Query of TNC along with the driver oncogenes of prostate tumorigenesis, including ERG, MYC and AR, in the aggressive neuroendocrine prostate cancer (NEPC) tumor whole genome sequencing datasets (N=77) demonstrating significant alterations (predominantly amplifications) in 74% of patient samples. CaP genomic levels TNC (30%) was significantly co-amplified (P &lt; 0.001) with ERG (27%), AR (56%) and MYC (53%). TNC protein expression was detected in all examined prostate cancer cell lines VCaP, LNCaP, PC3 and DU145.

Conclusion: Genomic alterations of TNC was thus associated with major oncogenic drivers of CaP, such as ERG, AR and MYC in NEPC genomic datasets. Multi-analyte serum biomarkers offers new opportunities with potential impact on primary treatment and surveillance strategies. Functional involvement of the analytes in disease progression to address their mechanistic link with major CaP oncogenic pathways will be further investigated.

Citation Format: Prachi Mishra, Michael Kebish, Jennifer Cullen, Amina Ali, Alagasamy Srinivasan, Inger Rosner, David McLeod, Leonardo Rodrigues, Viatcheslav Akmaev, Rangaprasad Sarangarajan, Shiv Srivastava, Niven Narain, Albert Dobi. Recurrent alterations of the TenascinC in highly aggressive neuroendocrine sub-type of 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 2772.

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 2626: Exquisite specificity of PMEPA1 isoforms in regulation of androgen signaling through AR protein degradation in prostate cancer

Introduction: Prostate Transmembrene Protein, androgen Induced 1 (PMEPA1) gene was defined as an androgen and TGF-β responsive gene to inhibit androgen receptor (AR) and TGF-β signaling via negative feedback loops. Our previous studies identified two functionally distinct PMEPA1 isoforms: androgen responsive PMEPA1-b and TGF-β responsive PMEPA1-a. These two isoforms share high homology within the intracellular domains including PY1 and PY2 motifs essential for binding to E3 ubiqintin ligase, NEDD4. It is still unclear which PMEPA1 isoform with distinct N-terminus regulates AR protein stability in CaP cells.

Methods: An immunoprecipitation (IP) assay was used to study the protein-protein interactions between AR, PMEPA1 isoforms and NEDD4. HEK293 cells were used for co-transfection of the expression vectors harboring PMEPA1 isoforms, AR and NEDD4. RNA Seq data from TCGA datasets were utilized to analyze the correlation between transcript levels of both PMEPA1 isoforms and clinical outcomes including Gleason scores, overall survival and progression free survival of cancers of prostate, breast, lung and colon.

Results: Only PMEPA1-b isoform bound to wild-type and T877A mutated AR, directly. In contrast, PMEPA1 isoforms a, b and c bound to E3 ubiquintin ligase NEDD4. As expected, only PMEPA1-b bound to AR and NEDD4 for tri-complex interactome. Interestingly, the direct binding between AR and NEDD4 was not detected, which highlighted the adaptor function of PMEPA1-b in mediating proteasome-mediated AR degradation. Furthermore, the deletion of the transmembrane domain compromised binding of PMEPA1-b with AR. The TGF-β responsive PMEPA1-a was not found to bind to AR or form AR/NEDD/PMEPA1 complex. Consistently, ectopic PMEPA1-b down-regulated AR protein, inhibited AR signaling, and suppressed cell growth of LNCaP cells. But PMEPA1-a was not detected to interfere with AR signaling in CaP cells. Clinically, a higher ratio of PMEPA1-a/b was correlated with higher Gleason scores in CaP. And higher expression of PMEPA1-a and b was associated with more aggressive lung cancer and colon cancer. All of these findings highly suggest that the biological functions of PMEPA1 isoforms on TGF-β or AR signaling are tissue specific.

Conclusions: Our study highlighted PMEPA1 isoform b as an essential docking platform by interacting with AR at N-terminus and NEDD4 at C-terminus for mediating the protein degradation of AR by NEDD4. Additionally, the transmembrane domain at N-terminus of PMEPA1-b protein was essential for NEDD4 dependent AR degradation. These findings might help guide a novel anti-AR strategy in development of anti-CaP therapy. RNA seq data analysis further underscored the tissue-specificity of division of labor among PMEPA1 isoforms in tum

Citation Format: Shashwat Sharad, Natashia Benjamin, Zsófia Sztupinszki, Zoltan Szallasi, Shiv Srivastava, Inger L. Rosner, Jennifer Cullen, Hua Li, Albert Dobi. Exquisite specificity of PMEPA1 isoforms in regulation of androgen signaling through AR protein degradation 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 2626.

Abstract 5305: Reexpression of LSAMP, a gene frequently deleted in African American prostate cancers, suppresses tumor growth and β-catenin activity

Introduction: African American (AA) men have the highest prostate cancer incidence and mortality rates in the US. The biological contribution to this disparity, however, is not well understood. LSAMP inactivation has been implicated in several cancers, and was recently identified in prostate cancer. A higher frequency of LSAMP inactivation has been observed in AA prostate cancer, and this aberration has been associated with a significantly greater risk of disease progression. In the characterization of LSAMP in prostate cancer cells lines, we found the copy number to be variable and the expression to be low or undetectable. LNCaP, MDA PCa 2B, and DU 145 prostate cancer cell lines were stably transduced to express LSAMP in an inducible or constitutive manner. LSAMP expression in these cell lines resulted in reduced cell proliferation, and induced a reversion to indolent cell-cell, and cell-extra-cellular-matrix adhesion characteristics, consistent with its tumor suppressive role. LSAMP expression also resulted in the down-regulation of receptor tyrosine kinases EPHA3, FGFR2, and FGFR4, and reduced activation of their downstream ERK and AKT pathways. Several Integrins were also up-regulated upon LSAMP expression. Additionally, β-catenin localization was altered, suggesting a potential reduction in transcriptional activity. We assessed the tumor suppressive function of LSAMP further, using in vitro assays and in vivo mouse models.

Methods: LSAMP expressing and control DU 145 cells were used to investigate the tumor suppressive function of LSAMP in vivo. Athymic nude mice were injected either subcutaneously, to determine effect of LSAMP expression on prostate tumor growth rates, or intravenously, to determine effect of LSAMP expression on tumor formation. We performed the TOPflash/FOPflash luciferase reporter assay to determine whether LSAMP expression modulates transcriptional activity of β-catenin in vitro.

Results: LSAMP expression resulted in a significant inhibition of tumor growth in the subcutaneous xenograft model. In the intravenous xenograft model, LSAMP expression resulted in a reduced incidence of distant metastases. Consistent with the negative modulation of signal transduction, and β-catenin localization previously observed, LSAMP expression resulted in a reduction of β-catenin transcriptional activity in vitro.

Conclusion: These studies provide in vivo evidence of the suppressive function of LSAMP in prostate tumors, corroborating previous in vitro and clinical findings. LSAMP expression reduced tumor growth rates, and incidence of distant metastases. LSAMP expression also reduced β-catenin transcriptional activity in vitro. These findings provide further support for a biological mechanism underlying the aggressive prostate cancer phenotype observed with LSAMP inactivation.

Citation Format: Kevin Babcock, Taduru Sreenath, Charles P. Xavier, Inger L. Rosner, Shiv Srivastava, Albert Dobi, Shyh-Han Tan. Reexpression of LSAMP, a gene frequently deleted in African American prostate cancers, suppresses tumor growth and β-catenin activity [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 5305.

ERG Tumor Type is Less Frequent in High Grade and High Stage Prostate Cancers of Chinese Men

Background: The incidence of prostatic adenocarcinoma has been rapidly increasing among Chinese men. This alarming trend prompted evaluations of early causal genomic alterations known to drive prostate tumorigenesis. Recurrent activation of the ETS-Related Gene (ERG) by genomic rearrangements is the most recognized early event in prostate cancer. Following the initial detection of ERG rearrangement at gene expression and genomic and levels, development of diagnostic quality antibodies against ERG oncoprotein have streamlined the rapid assessment of ERG frequencies world-wide. Unexpectedly, these studies revealed highest frequencies of ERG among Caucasian descents, lower frequencies among African Americans and even lower prevalence of ERG among Asian men.

Objective: To asses in a prospective study ERG frequencies, clinico-pathological and prognostic associations of ERG among prostate cancer patients of the Dalian region of Northeast China, by an established immunohistochemical procedure that have been used in studies world-wide.

Methods: Formalin fixed paraffin embedded specimens donated by patients (N=50) diagnosed with prostatic adenocarcinoma who underwent transurethral resection of the prostate (TURP) between 2007 and 2012 were evaluated for ERG by immunohistochemistry.

Results: Of the 50 cases, 13/50 (26.0%) tumors were positive for ERG. In all cases, normal prostatic epithelial were ERG negative. ERG was more frequently detected in the lower Gleason score (≤7) and low T-stage. Consistent with reports from Asian countries the results of our study shows lower overall frequencies of ERG positive tumors when compared to reports from Western countries.

Conclusion: The intriguing association of even lower ERG frequencies with high Gleason scores and higher T-stages provides impetus for current driver gene discoveries focused on the predominantly ERG negative prostate cancers of Asian men.

PMEPA1 gene isoforms to indicate disease progression in solid tumors

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Background: Dysfuncitons of androgen and TGF-β signaling play important roles in prostate tumorigenesis. PMEPA1 gene has been defined as an androgen and TGF-β responsive gene which inhibits androgen and TGF-β signaling via negative feed-back loops. Our previous data has established that PMEPA1 distinct isoforms ( PMEPA1-a and PMEPA1-b) with disparities within N-terminus protein sequences navigate different androgen/TGF-β signaling regulations. In this study, the roles of PMEPA1 isoforms in disease progressions were investigated in solid tumors of prostate (CaP), breast, lung and colon. Methods: RNA seq data from total 2479 solid tumor samples in the TCGA dataset were used to study the correlation between expressions of PMEPA1 isoforms and disease progression including Gleason score, pathology stages, progression free survival rate (PFS) and overall survival rate (OS). The cohort is composed of 482 prostate, 1049 breast, 499 lung and 449 colon cancer patients. Results: In CaP, the TCGA data analysis showed that lower transcript level of PMEPA1-b isoform associated with higher Gleason scores and lower progression free survival rate (PFS) (P = 0.014) and worse overall survival rate (OS) (P < 0.01). The ratio of mRNA levels of PMEPA1-a versus PMEPA-b indicated higher Gleason score, lower PFS rate (P = 0.0063) and worse OS rate (P = 0.0042). In contrast, higher expression of both PMEPA1-a and PMEPA- b associated with lower PFS (P = 0.023 and 0.028, respectively) in breast cancer. And the enhanced ratio of PMEPA1-a/ b was also found to indicate lower PFS (P = 0.016) and worse OS (P = 0.016) in breast cancer. Similarly, the increased transcript levels of PMEPA1-a and PMEPA1-b isoforms significantly associated with lower PFS and worse OS rates in lung and colon cancer. The expression of PMEPA1 isoforms was not found to associate with pathology stages of diseases. Conclusions: Our data establish the biomarker potential of PMEPA1 gene isoforms ( a and b) indicating more aggressive disease progressions in 4 solid tumors, further underscoring the PMEPA1 isoform specific biological functions to differentiate regulation of androgen and TGF-β signaling in cancer cells.

Increased Smad3 and reduced Smad2 levels mediate the functional switch of TGF-β from growth suppressor to growth and metastasis promoter through TMEPAI/PMEPA1 in triple negative breast cancer

Screening of several TNBC cell lines showed altered Smad2 and Smad3 protein levels compared to normal mammary epithelial cells, suggesting the possibility that it could play an important role in the escape of cancer cells from TGF-β mediated growth inhibition. To assess the functional relevance of these endogenous molecules, Smad2 or Smad3 expression was knocked down individually and assessed their effects on pro-oncogenic properties of TGF-β. Smad3 deficiency reduced growth and invasion capacity of breast cancer cells in comparison to Smad2 which had no effect. Smad3 deficiency was also found to be associated with a reduction in the expressions of TMEPAI/PMEPA1 and EMT inducing transcription factors, E-Cadherin and increased expression of cell cycle inhibitors and Vimentin. On the other hand, Smad2 deficiency had opposite effect on these regulators. Interestingly, the decreased growth, invasion and associated gene expressions were largely reversed by overexpressing TMEPAI in Smad3 knockdown cells, suggesting that Smad3-TMEPAI axis may be involved in subverting growth suppressive effects of TGF-β into growth promotion. Similarly, altered levels of Smad proteins and TMEPAI were also noted in primary TNBC tumor tissues. Analysis of the existing databases provided additional support in terms of TMEPAI and Smad2 expression impacting the survival of TNBC patients. Taken together, our data demonstrate a novel role for Smad3 in cancer transformation and cancer progression through TMEPAI and further suggest that selective targeting of TGF-β-Smad3-TMEPAI axis may be beneficial in triple negative breast cancer therapy and prevention.

Abstract A010: ETS-related gene mediated androgen receptor aggregation and endoplasmic reticulum stress in prostate cancer development

Introduction: AR-mediated activation of ETS Related Gene (ERG) represents one of the most common and validated prostate cancer driver genes. Recently, we have shown novel morphologic phenotypes of endoplasmic reticulum (ER) stress in prostate glands of ARR2PB-ERG transgenic mouse. Since AR regulates ERG expression through TMPRSS2 promoter in human prostate cancer, we continue to investigate the post-translational interactions between ERG and AR leading to ER stress and subsequently to cell survival mechanisms. Understanding these mechanisms will potentially have major therapeutic implications.

Methods: Light and electron microscopy were used to examine the morphologic and subcellular differences. AR aggregations, Co-IP and Proximal Ligation Assay for protein-protein interactions were studied in LNCaP, HEK293 cells. N-terminal and C-deletions of AR were utilized to identify specific AR domain interactions with ERG. Luminal cell surface markers on the isolated mouse prostate glands and spontaneously immortalized mouse prostate epithelial cells from ERG transgenic mouse (MoE1) were analyzed by FACS analysis.

Results: Coexpression of ERG and AR showed significant aggregation of AR in filter assays. Co-IP experiments and PLA assays revealed that significant interactions occur through N-terminal domain of AR with ERG. Epithelial cells of ERG-Tg mouse prostates showed ~70% increase in CD49f (low) and Sca-1 (med) population with increased sphere formation capability and resistance to radiation-induced cell death. Both epithelial cells grown into spheres and established MoE1 cells displayed increased CD49f (low) and significant increase in the EpCAM negative population.

Conclusions: Overall, our experiments demonstrate the mechanistic link that the physical interactions between ERG and AR lead to ER stress in prostate epithelium through AR misfolding/aggregation. Our observations of ERG-induced AR aggregation as one of the initial events that lead to ER stress and to cell survival indicate a critical function for ERG in the etiology of prostate cancer initiation and progression.

Citation Format: Taduru L. Sreenath, Shiela S. Macalindong, Natallia Mikhalkevich, Shashwat Sharad, Ahmed Mohamed, Denise Young, Borbiev Talaibek, Charles Xavier, Rishita Gupta, Muhammad Jamal, Kevin Babcock, Shyh-Han Tan Tan, Marja T. Nevalainen, Albert Dobi, Gyorgy Petrovics, Isabell A. Sesterhenn, Inger L. Rosner, Charles J. Bieberich, Peter Nelson, Valeri Vasioukhin, Shiv Srivastava. ETS-related gene mediated androgen receptor aggregation and endoplasmic reticulum stress in prostate cancer development [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 A010.

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 A018: Distinct genomic alterations in prostate cancer of African American men

Background: In recent years remarkable ethnic/racial differences in the frequency of prostate cancer (CaP) driver gene alterations have emerged. Along the lines of ethnic differences in CaP genomes, oncogenic activation of ERG proto-oncogene and deletion of the PTEN tumor suppressor gene are most widely studied. These findings underscore distinct biology of prostate cancer in different ethnicities and races. We have reported the cumulative analyses of 435 patients (whole genome sequencing (WGS): 14, FISH evaluations: 101, SNP array: 320) comparing CaP genomes of African American (AA) and Caucasian American (CA) patients. An AA CaP genome-associated deletion was identified and mapped to the Limbic System-Associated Membrane Protein (LSAMP) gene locus. Further examination of the data indicated the AA CaP-genome associated deletion of the Chromodomain Helicase DNA Binding Protein 1(CHD1) gene. The goal of the current study is the comparative assessment of frequencies and prognostic associations of CaP genome alterations in the context of racial/ethnic differences.

Methods: A prostate tumor tissue microarray (TMA) of benign and tumor foci (500+ cores) was generated by sampling 2-3 cores representing the range of cell morphology in matched cohort of 42 AA and 59 CA patients with up to 20 years of follow-up. Comparative evaluation of frequencies and prognostic associations of ERG oncoprotein by immunohistochemistry and the deletion of LSAMP, CHD1, and PTEN genes by FISH was performed. ERG frequencies were further assessed in index tumors of Chinese CaPs (N=100) and were compared to ERG frequencies in index tumors of patients from the United States equal-access military health-care system (N=336 AA and N=594 CA).

Results: Higher frequencies of recurrent deletions of CHD1 (29% AA vs. 10% CA p=0.017) and LSAMP (26% AA vs. 7% CA, p=0.006) were identified in AA CaP compared to CA CaPs. These deletions were associated with significantly higher risk of rapid biochemical recurrence. In contrast, PTEN deletions (15% AA vs. 63% CA) and the frequency of ERG positive CaPs (26% AA vs. 64% CA) were more frequent among CA CaPs. Comparative evaluation of ERG frequencies in CaPs (N=1,292) underscores highest ERG frequency 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. Higher frequency of CHD1 deletion in CaPs of AA patients may provide new therapeutic opportunities due to the sensitivity of CHD1 deletion harboring tumors to PARP inhibitors and platinum agents.

Acknowledgments: This research was supported by the CPDR-USU program HU0001-10-2-0002, the National Cancer Institute R01CA162383 grant, the EDRN/NCI ACN12011-001-0 grant, the Snyder Medical Foundation, the Otto Mønsteds Foundation, the Mazzone Foundation, the Breast Cancer Research Foundation, the Novo Nordisk Foundation, and grants by MTA-TKI643/2012, KTIA_NAP_13-2014-0021.

Citation Format: Albert Dobi, Gyorgy Petrovics, Hua Li, Denise Young, Shyh-Han Tan, Yongmei Chen, Qingyu Xiao, Yidi Sun, Hong Li, Yixue Li, Yuan Ji, Jun Hou, Wendy Wang, Jacob Kagan, Guo-Ping Zhao, Sudhir Srivastava, Reinhard Ebner, Inger L. Rosner, Jennifer Cullen, Matthew Freedman, Isabell Sesterhenn, Zoltan Szallasi, Shiv Srivastava. Distinct genomic alterations in prostate cancer of African American men [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 A018.

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 2573: Selection of candidate biomarkers for aggressive prostate cancer based on targeted proteomics

Mass spectrometry based targeted proteomics such as selected reaction monitoring (SRM) provides an effective, antibody-independent strategy for sensitive, specific and multiplexed verification of genomics biomarker candidates at the protein level. In order to identify a panel of proteins with the potential to predict prostate cancer progression, we have selected 52 protein candidates from existing prostate cancer genomics data sets and validated cancer drivers, and performed quantitative proteomics analysis in tissue samples using the highly sensitive PRISM (high-pressure, high-resolution separations coupled with intelligent selection and multiplexing)-SRM approach. PRISM-SRM assays have been developed for the 52 prostate cancer biomarker candidates including: prostate cancer relevant genes and common cancer drivers. One set of 105 formalin-fixed paraffin-embedded (FFPE) whole mount prostate tissue specimens were analyzed using PRISM-SRM with heavy isotope-labeled synthetic peptides as internal standards: 20 primary tumors from patients showing metastatic progression, 37 primary tumors from patients who showed biochemical recurrence (BCR), and 48 primary tumors from patients with no BCR or metastatic progression after more than ten years of follow-up after radical prostatectomy. Overall, PRISM-SRM analyses of the FFPE tissue samples enabled the detection of 42 out of 52 biomarker candidates; in comparison regular LC-SRM without the front-end chromatographic enrichment could detect only 21 of these candidates at the protein level. Kruskal-Wallis test of the PRISM-SRM results provided a statistical evaluation of comparison of relative protein levels among the “no progression”, BCR and “metastatic progression” groups. Prostate differentiation/AR signaling related proteins (FOLH1, PSA and NCOA) or tumor progression (TGFB1, CCND1 and SPRC) were significantly different between the three groups. These promising biomarker candidates for early detection of aggressive prostate cancer are being further evaluated, individually and in panels, in an independent cohort of 234 samples for their potential prognostic applications. In summary, PRISM-SRM provides a highly sensitive method for quantification and rapid screening of promising cancer biomarker candidates defined by multiomics platforms.

Citation Format: Yuqian Gao, Hui Wang, Jennifer Cullen, Yongmei Chen, Athena Schepmoes, Gyorgy Petrovics, Thomas Fillmore, Tujin Shi, Wei-Jun Qian, Richard Smith, Sudhir Srivastava, Jacob Kagan, Albert Dobi, Karin Rodland, Shiv Srivastava, Tao Liu. Selection of candidate biomarkers for aggressive prostate cancer based on targeted proteomics [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 2573.

Abstract 2797: Synthesis and evaluation of derivatives of selective inhibitor ERGi USU, for ERG-positive prostate cancer cells

Introduction and objectives:

Prostate cancer is the most frequently diagnosed non-skin malignancy and third leading cause of cancer related deaths among men in the United States. Currently, early detected organ confined prostate cancer (CaP) is managed by active surveillance, surgery or radiation therapy. A significant subset of patients (20% to 40%) experience biochemical recurrence after definitive treatment. New AR axis inhibitors (abiraterone and enzalutamide) are leading to significant improvements in treatment of late stages of CaP. However, sustained therapeutic response remains a challenge due to high mutation load at late stages of the disease. Thus, there is an urgent need for evaluating new therapeutic targets for early stages of CaP. ERG oncoprotein and ERG dependent pathways are promising targets for early stage cancer therapy. Previously identified ERGi-USU from our laboratory, demonstrated remarkable exclusivity for inhibiting ERG protein and cell growth of ERG positive tumor cells in both in vitro and in vivo. With comprehensive structure activity relationship (SAR) studies, we generated new derivatives with substituents around the core structure to further enhance efficacy.

Methods: Cell growth inhibition of small molecules was validated with established prostate cancer cell lines and normal prostate/endothelial derived cell panel. Preferential species-specific binding of ERGi-USU to human RIOK2 was confirmed by tryptophan fluorescence quenching assay.

Result: Based on SAR of the parental ERGi-USU, 90 new ERGi-USU derivatives were designed using structure based predictions. Of these, 37 compounds were prioritized for chemical synthesis and biological evaluations using assays that were developed earlier in our laboratory. We completed primary screen of these compounds in cell culture models. Among these one compound (ERGi-USU-6) inhibited the growth of ERG positive prostate cancer cells with remarkable improvement IC50=70 nM. This value is in the range of current FDA approved drugs. The result also confirmed the high selectivity of ERGi-USU-6 for the inhibition of ERG positive cancer cell growth. Further, mechanistic studies revealed ERGi-USU binding and disruption of the atypical RIOK2 kinase basic function of ribosome biogenesis, due to initiation of ribosomal stress, cell cycle arrest and apoptosis in ERG positive VCaP cells. We also demonstarte preferential binding of ERGi-USU to human RIOK2 by tryptophan fluorescence quenching assay.

Conclusion: The ERGi-USU-6, derivative of ERGi-USU showed improved efficacy in selectively inhibiting the growth of ERG positive cancer cells. Since ERG is a prostate cancer causing oncogene that affects approximately one third of CaP patients world-wide, early therapeutic intervention with ERGi-USU derivatives may prevent the development of late stage disease in prostate cancer patients.

Citation Format: Charles Peter Xavier, Ahmed A. Mohamed, Nishat Seraj, Vineet Kumar, Taduru Sreenath, Inger L. Rosner, Gyorgy Petrovics, Meera Srivastava, Clifton L. Dalgard, Sanjay V. Malhotra, Nicole A. LaRonde, Albert Dobi, Shiv Srivastava. Synthesis and evaluation of derivatives of selective inhibitor ERGi USU, for ERG-positive prostate cancer cells [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 2797.

Abstract 5765: Immunobiomarkers: Structural and functional characterization of single chain fragment variable (scFv) to ERG from a mouse monoclonal antibody

Introduction: Biomarkers for early detection, disease stratification as well as treatment strategies are a major area of focus in prostate cancer (CaP) research. The gene fusion involving ERG and the TMPRSS2 gene promoter contributes to expression of ERG in CaP, serving as a biomarker for CaP. This led to the development of monoclonal or polyclonal antibodies against ERG protein for diagnostic or therapeutic purposes. As the use of intact monoclonal antibody is limited due to large size and low cell penetration, we hypothesized that single chain fragment variable (scFv) and single domain antibody (sdAb) known as minibodies will be valuable as therapeutic agents targeting ERG protein. Towards this goal, the present study addresses the following: i) Characterization of variable heavy (VH) and variable light (VL) chain sequences and generation of expression vectors; ii) Assessing the specificity of binding of scFv and sdAb to ERG protein; iii) Functional evaluation of scFv and sdAb in cellsMethods: We generated VH and VL encoding sequences using RNA derived from hybridoma cells secreting anti-ERG monoclonal antibody designated 9FY. scFv-9FY and sdAb-9FY fragments represent scFv and sdAb , respectively were cloned in an eukaryotic and prokaryotic expression vectors. The proteins (scFv and sdAb) were analyzed by western blot and ELISA. The binding of scFv and sdAb to ERG protein in live cells was evaluated by bimolecular fluorescence complementation (BiFC) assay. Biological effects of scFv and sdAb were assessed in HEK293, VCaP and LNCaP cells. Results: Analysis was carried out to determine the primary DNA sequence of scFv fragments. Using the predicted amino acid sequence, we identified CDR1, CDR2 and CDR3 regions. scFv expressed in prokaryotic vector was purified and used for the evaluation of immunoreactivity to ERG by ELISA. The affinity of scFv and sdAb to ERG was demonstrated through their binding to ERG protein in HEK293 cells by using BiFC assay. This involved the generation of chimeric proteins in which scFv or sdAb coding sequences were fused in-frame to the Venus N- or C-terminal segment separated by a flexible linker of 10 amino acids. Minibodies scFv and sdAb, upon introduction into VCaP cells through transfection, showed cytotoxic effects similar to the observations noted with siRNA against ERG.Conclusions: Here we showed that scFv and sdAb minibodies exhibit high affinity for ERG protein. This property enables them to disrupt the functions mediated by ERG in cells. Given the prevalence of ERG overexpression in prostate cancer, the novel agents based on scFv and sdAb have the potential to interfere with the effect or functions of ERG and are likely to be beneficial in the treatment of CaP.

Source of Funding: Center for Prostate Disease Research, USU Grant HU0001-10-2-0002, NCI/EDRN Grant ACN12011-001-0, and the NCI Grant R01CA162383.

Citation Format: Shyh-Han Tan, Anshu Rastogi, Sreedatta Banerjee, Annie Bagga, Charles Xavier, Ahmed Mohamed, Denise Young, Gyorgy Petrovics, Albert Dobi, Isabell A. Sesterhenn, Jacob Kagan, Sudhir Srivastava, David G. David, Inger L. Rosner, Shiv Srivastava, Alagarsamy Srinivasan. Immunobiomarkers: Structural and functional characterization of single chain fragment variable (scFv) to ERG from a mouse monoclonal antibody [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 5765.

Abstract LB-219: Clinical utility of a serum protein biomarker panel (FLNA, KRT19) in stratification of prostate cancer from benign prostate hyperplasia patients

Background: Prostate-specific antigen (PSA) based screening tests have been considered as a benchmark for PCa diagnosis (PSA &gt;4 ng/mL), however, in recent years their use has been widely debated due to various limitations. In particular, increased PSA levels are also observed in patients with benign prostatic hyperplasia (BPH) thus generating a false positive. These patients are often subjected to unnecessary prostate biopsies and have to endure both physical and mental anguish. Thus, there is a clear unmet need to develop molecular diagnostics that stratifies men with BPH from those that have PCa and prevent unwarranted prostate biopsies in symptomatic, DRE negative men. Here in, we demonstrate clinical utility of a validated biomarker panel (FLNA, KRT 19) in combination with age and prostate volume in stratifying BPH from PCa patients.

Methods: This study was conducted using retrospectively collected and clinically annotated serum samples from 203 BPH patients and 333 PCa patients with PSA values ranging from 4-10ng/mL. These samples included BPH patients with negative Digital Rectum Exam, single biopsy and repeat biopsies, and prostate cancer patients undergoing radical prostatectomy. Validated bioanalytical assays (FLNA ELISA, FLNA IPMRM and KRT19 ELISA) were used to quantitate the serum biomarkers. Regression models were built and compared for their ability to distinguish patients with BPH from those with PCa.

Results: Table 1: Summary of predictive power analysis of PCa panel (49 characters)

BERG TestPSAAUC0.80.54Sensitivity0.8n/aSpecificity0.62n/aPPV0.78n/aNPV0.65n/aOR (CI)6.67 (4.49,9.90)n/a

Conclusion: The data demonstrates that these PCa biomarkers in combination with age, and prostatic volume were significantly better than (0.8) PSA (0.54 AUC in this population) in identifying men with BPH rather than PCa thus preventing unnecessary biopsies for this population. Moreover, this panel may be used in clinical decision support to physicians to fill a clinical unmet need.

Citation Format: Michael A. Kiebish, Poornima Tekmulla, Shobha Ravipaty, Wenfang Wu, Tracey Friss, Chenchen Liao, Allison Klotz, Joe Andreazi, Elisabeth Hutchins, Albert Dobi, Shiv Srivastava, Jennifer Cullen, Amina Ali, Stephen Freedland, Kagan Griffin, Sandra Laszlo, Michele Petrovic, Neil Fleshner, Jeonifer Garren, Leonardo Rodrigues, Mark D. Kellog, Viatcheslav R. Akmaev, Rangaprasad Sarangarajan, Niven R. Narain. Clinical utility of a serum protein biomarker panel (FLNA, KRT19) in stratification of prostate cancer from benign prostate hyperplasia patients [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 LB-219.

Abstract 2636: Combined MRI and molecular signatures of prostate cancer: Association with biochemical recurrence

Purpose: To assess the correlation of histologic and prostate cancer associated gene oncoprotein expression and imaging features in MRI-detected lesions of prostate cancer patients with biochemical recurrence (BCR) after definitive treatment.

Methods: Patients underwent multiparametric MRI (mpMRI) at 3T at a single institution prior to TRUS/MRI fusion-guided biopsy of MRI-defined index lesions and prior to definitive therapy (radical prostatectomy), for which clinical follow-up was available. All mpMRI lesions were prospectively scored low, moderate, moderate-high, or high for suspicion of harboring clinically significant cancer, as determined by positivity on individual MRI sequences and indication of extraprostatic extension (EPE) on imaging. The expression of prostate cancer drivers (ERG, PTEN, AR and p53) and PSA were examined on targeted-biopsy specimens by immunohistochemistry (IHC). All histological assessments were completed blinded to imaging findings and treatment outcomes. Cox proportional hazard regression was used to evaluate associations between imaging, molecular, and surgical characteristics with interval to BCR.

Results: In a preliminary cohort of 56 patients, 29 patients met clinical criteria for BCR (median interval 12.46 months, range 1-55 months) and 27 patients remain recurrence-free (median follow-up 30.75 months, range 1-72+ months). Median interval between mpMRI and targeted biopsy was 29 days (range 12-167 days) and radical prostatectomy was 4.13 months (range 1.3-8.0 months). Pre-operative serum PSA was the strongest correlate with time to BCR (HR: 1.63, 95%-CI: 12.-2.1, p&lt;0.0001). The p53 staining intensity 3+ in &gt;1% of cells or 2+ in &gt;10% of cells was associated with poor BCR interval (HR: 3.35, 95%-CI: 1.5-7.2, p=0.002), remaining so in multivariate model with pre-operative MRI, PSA, and post-surgical findings on pathology. p53 positivity was observed more frequently in Gleason≥4+3, for both biopsy (fisher's exact p=0.006) and final pathology grading (fisher's exact p=0.01). Moderate/high to high index MRI suspicion was found to correlate with EPE at surgery (fisher's exact p=0.03) and showed modest correlation to time-to-BCR in univariate analysis (HR: 2.11, 95%-CI: 0.99-4.5, p= 0.052) and remained so in multivariate analysis. PTEN loss was observed in 8 patients (14%). PSA+ expression by IHC was observed in 49/56 patients, with remaining 7 patients showing variable/heterogeneous (PSA+/-) expression.

Conclusions: MRI impression and p53 status from MRI index lesion were independent predictors of time to biochemical recurrence, along with pre-operative PSA levels. These results are part of an ongoing study to identify histo-radiological features of aggressive prostate cancers.

Citation Format: Stephanie A. Harmon, William Gesztes, Denise Young, Sherif Mehralivand, Brad J. Wood, Peter A. Pinto, Gyorgy Petrovics, Albert Dobi, Inger L. Rosner, Baris Turkbey, Shiv Srivastava, Peter L. Choyke, Isabelle A. Sesterhenn. Combined MRI and molecular signatures of prostate cancer: Association with biochemical recurrence [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 2636.

Abstract 4486: Reexpression of LSAMP, a gene frequently deleted in African American prostate cancers, alters adhesive qualities of prostate tumor cells and inhibits Akt, ERK1/2, and β-Catenin signaling axis

INTRODUCTION: Although African American (AA) men have the highest prostate cancer (CaP) incidence and mortality rates in the US, most studies of CaP genome have been performed using tumor specimens from Caucasian Americans (CA). To address the underrepresentation of AA CaP in these studies, we performed whole genome sequencing, IHC and FISH validation on tissue microarrays, and analysis of TCGA data, on a total of 438 CaPs. We noted less frequent alterations of two common CaP driver genes, PTEN and ERG, in CaP genomes of AA compared to CA men, confirming earlier observations by others and us. We reported a higher frequency of a genomic deletion of the Limbic System Associated Membrane Protein (LSAMP) gene, located on 3q13.31 locus in AA CaP, which was also associated with rapid biochemical recurrence. A recent study of CaP genome in a Chinese cohort detected LSAMP alterations at a frequency similar to that in our AA cases. LSAMP loss in other cancers have been associated with aggressive disease. We hypothesize that the loss of LSAMP contributes to CaP progression. Here, we report further biological evaluations of LSAMP modulation in CaP cells.

METHODS: The copy number and expression of LSAMP in CaP cell lines were assessed. We established stable doxycycline inducible LSAMP expression in LNCaP and in MDA PCa 2b cells (AA patient derived cell line with monoallelic LSAMP deletion), and constitutive expression in DU145 cells. We assessed the effect of LSAMP expression on cell-cell adhesion by monitoring the binding of LSAMP expressing and control DU145 cells to mouse fibroblast (NIH-3T3), normal human prostate stroma (WPMY-1), human endothelial (HUVEC), and human bone marrow stroma (HS-5) cells. We analyzed LSAMP modulated signaling pathways in the inducible and constitutively LSAMP expressing cell lines by immunoblot and immunofluorescence assays.

RESULTS: Overexpression of LSAMP resulted in attenuated cell proliferation and increased adhesion of cells to extracellular matrix proteins. LSAMP expression in DU145 cells increased their adhesion to fibroblast and prostate stroma cell lines, and concomitantly decreased their adhesion to endothelial, and bone marrow stroma cells. LSAMP expression resulted in decreased expression of FGFR2, FGFR4, and EphA3 receptor tyrosine kinases, and decreased phosphorylation of their downstream targets in Akt and ERK1/2 signaling pathways, leading to the inactivation of β-catenin. LSAMP expression also alters the levels of some Integrins.

CONCLUSION: Cell biologic features of LSAMP reported here, along with observations of genomic inactivations of LSAMP in CaP support its role in CaP progression through altered cell adhesion. These data provide the first insight into LSAMP function in CaP, corroborating with studies that suggest bona fide tumor suppressor function for LSAMP in cancers.

Citation Format: Kevin Babcock, Inger L. Rosner, Shiv Srivastava, Albert Dobi, Shyh-Han Tan. Reexpression of LSAMP, a gene frequently deleted in African American prostate cancers, alters adhesive qualities of prostate tumor cells and inhibits Akt, ERK1/2, and β-Catenin signaling axis [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 4486.

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 B57: Distinct genomic alterations in prostate cancer of African American men

This abstract is being presented as a short talk in the scientific program. A full abstract is printed in the Proffered Abstracts section (PR01) of the Conference Proceedings.

Note: This abstract was not presented at the conference.

Citation Format: Albert Dobi, Gyorgy Petrovics, Hua Li, Denise Young, Yongmei Chen, Jacob Kagan, Sudhir Srivastava, Reinhard Ebner, Inger L. Rosner, Jennifer Cullen, Matthew L. Freedman, Isabell A. Sesterhenn, Zoltan Szallasi, Shiv Srivastava. Distinct genomic alterations in prostate cancer of African American men [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 B57.

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.