Prostate Cancer Genomics: Recent Advances and the Prevailing Underrepresentation from Racial and Ethnic Minorities.

Prostate cancer (CaP) is the most commonly diagnosed non-cutaneous cancer and the second leading cause of male cancer deaths in the United States. Among African American (AA) men, CaP is the most prevalent malignancy, with disproportionately higher incidence and mortality rates. Even after discounting the influence of socioeconomic factors, the effect of molecular and genetic factors on racial disparity of CaP is evident. Earlier studies on the molecular basis for CaP disparity have focused on the influence of heritable mutations and single-nucleotide polymorphisms (SNPs). Most CaP susceptibility alleles identified based on genome-wide association studies (GWAS) were common, low-penetrance variants. Germline CaP-associated mutations that are highly penetrant, such as those found in HOXB13 and BRCA2, are usually rare. More recently, genomic studies enabled by Next-Gen Sequencing (NGS) technologies have focused on the identification of somatic mutations that contribute to CaP tumorigenesis. These studies confirmed the high prevalence of ERG gene fusions and PTEN deletions among Caucasian Americans and identified novel somatic alterations in SPOP and FOXA1 genes in early stages of CaP. Individuals with African ancestry and other minorities are often underrepresented in these large-scale genomic studies, which are performed primarily using tumors from men of European ancestry. The insufficient number of specimens from AA men and other minority populations, together with the heterogeneity in the molecular etiology of CaP across populations, challenge the generalizability of findings from these projects. Efforts to close this gap by sequencing larger numbers of tumor specimens from more diverse populations, although still at an early stage, have discovered distinct genomic alterations. These research findings can have a direct impact on the diagnosis of CaP, the stratification of patients for treatment, and can help to address the disparity in incidence and mortality of CaP. This review examines the progress of understanding in CaP genetics and genomics and highlight the need to increase the representation from minority populations.

Prostate cancer marker panel with single cell sensitivity in urine.

BACKGROUND: Over one million men undergo prostate biopsies annually in the United States, a majority of whom due to elevated serum PSA. More than half of the biopsies turn out to be negative for prostate cancer (CaP). The limitations of both the PSA test and the biopsy procedure have led to the development for more precise CaP detection assays in urine (e.g., PCA3, TMPRSS2-ERG) or blood (e.g., PHI, 4K). Here, we describe the development and evaluation of the Urine CaP Marker Panel (UCMP) assay for sensitive and reproducible detection of CaP cells in post-digital rectal examination (post-DRE) urine. METHODS: The cellular content of the post-DRE urine was captured on a translucent filter membrane, which is placed on Cytoclear slides for direct evaluation by microscopy and immuno-cytochemistry (ICC). Cells captured on the membrane were assayed for PSA and Prostein expression to identify prostate epithelial cells, and for ERG and AMACR to identify prostate tumor cells. Immunostained cells were analyzed for quantitative and qualitative features and correlated with biopsy positive and negative status for malignancy. RESULTS: The assay was optimized for single cell capture sensitivity and downstream evaluations by spiking a known number of cells from established CaP cell lines, LNCaP and VCaP, into pre-cleared control urine. The cells captured from the post-DRE urine of subjects, obtained prior to biopsy procedure, were co-stained for ERG, AMACR (CaP specific), and Prostein or PSA (prostate epithelium specific) rendering a whole cell based analysis and characterization. A feasibility cohort of 63 post-DRE urine specimens was assessed. Comparison of the UCMP results with blinded biopsy results showed an assay sensitivity of 64% (16 of 25) and a specificity of 68.8% (22 of 32) for CaP detection by biopsy. CONCLUSIONS: This pilot study assessing a minimally invasive CaP detection assay with single cell sensitivity cell-capture and characterization from the post-DRE urine holds promise for further development of this novel assay platform. Prostate 75: 969-975, 2015. © 2015 The Authors. The Prostate, published by Wiley Periodicals, Inc.

Analytical platform evaluation for quantification of ERG in prostate cancer using protein and mRNA detection methods.

BACKGROUND: The established methods for detecting prostate cancer (CaP) are based on tests using PSA (blood), PCA3 (urine), and AMACR (tissue) as biomarkers in patient samples. The demonstration of ERG oncoprotein overexpression due to gene fusion in CaP has thus provided ERG as an additional biomarker. Based on this, we hypothesized that ERG protein quantification methods can be of use in the diagnosis of prostate cancer. METHODS: An antibody-free assay for ERG3 protein detection was developed based on PRISM (high-pressure high-resolution separations with intelligent selection and multiplexing)-SRM (selected reaction monitoring) mass spectrometry. We utilized TMPRSS2-ERG positive VCaP and TMPRSS2-ERG negative LNCaP cells to simulate three different sample types (cells, tissue, and post-DRE urine sediment). Enzyme-linked immunosorbent assay (ELISA), western blot, NanoString, and qRT-PCR were also used in the analysis of these samples. RESULTS: Recombinant ERG3 protein spiked into LNCaP cell lysates could be detected at levels as low as 20 pg by PRISM-SRM analysis. The sensitivity of the PRISM-SRM assay was approximately 10,000 VCaP cells in a mixed cell population model of VCaP and LNCaP cells. Interestingly, ERG protein could be detected in as few as 600 VCaP cells spiked into female urine. The sensitivity of the in-house ELISA was similar to the PRISM-SRM assay, with detection of 30 pg of purified recombinant ERG3 protein and 10,000 VCaP cells. On the other hand, qRT-PCR exhibited a higher sensitivity, as TMPRSS2-ERG transcripts were detected in as few as 100 VCaP cells, in comparison to NanoString methodologies which detected ERG from 10,000 cells. CONCLUSIONS: Based on this data, we propose that the detection of both ERG transcriptional products with RNA-based assays, as well as protein products of ERG using PRISM-SRM assays, may be of clinical value in developing diagnostic and prognostic assays for prostate cancer given their sensitivity, specificity, and reproducibility.

Evaluation of ERG responsive proteome in prostate cancer.

BACKGROUND: Gene fusion between TMPRSS2 promoter and the ERG proto-oncogene is a major genomic alteration found in over half of prostate cancers (CaP), which leads to aberrant androgen dependent ERG expression. Despite extensive analysis for the biological functions of ERG in CaP, there is no systematic evaluation of the ERG responsive proteome (ERP). ERP has the potential to define new biomarkers and therapeutic targets for prostate tumors stratified by ERG expression. METHODS: Global proteome analysis was performed by using ERG (+) and ERG (-) CaP cells isolated by ERG immunohistochemistry defined laser capture microdissection and by using TMPRSS2-ERG positive VCaP cells treated with ERG and control siRNA. RESULTS: We identified 1,196 and 2,190 unique proteins stratified by ERG status from prostate tumors and VCaP cells, respectively. Comparative analysis of these two proteomes identified 330 concordantly regulated proteins characterizing enrichment of pathways modulating cytoskeletal and actin reorganization, cell migration, protein biosynthesis, and proteasome and ER-associated protein degradation. ERPs unique for ERG (+) tumors reveal enrichment for cell growth and survival pathways while proteasome and redox function pathways were enriched in ERPs unique for ERG (-) tumors. Meta-analysis of ERPs against CaP gene expression data revealed that Myosin VI and Monoamine oxidase A were positively and negatively correlated to ERG expression, respectively. CONCLUSIONS: This study delineates the global proteome for prostate tumors stratified by ERG expression status. The ERP data confirm the functions of ERG in inhibiting cell differentiation and activating cell growth, and identify potentially novel biomarkers and therapeutic targets.

Loss of the NKX3.1 tumorsuppressor promotes the TMPRSS2-ERG fusion gene expression in prostate cancer.

BACKGROUND: In normal prostate epithelium the TMPRSS2 gene encoding a type II serine protease is directly regulated by male hormones through the androgen receptor. In prostate cancer ERG protooncogene frequently gains hormonal control by seizing gene regulatory elements of TMPRSS2 through genomic fusion events. Although, the androgenic activation of TMPRSS2 gene has been established, little is known about other elements that may interact with TMPRSS2 promoter sequences to modulate ERG expression in TMPRSS2-ERG gene fusion context. METHODS: Comparative genomic analyses of the TMPRSS2 promoter upstream sequences and pathway analyses were performed by the Genomatix Software. NKX3.1 and ERG genes expressions were evaluated by immunoblot or by quantitative Real-Time PCR (qRT-PCR) assays in response to siRNA knockdown or heterologous expression. QRT-PCR assay was used for monitoring the gene expression levels of NKX3.1-regulated genes. Transcriptional regulatory function of NKX3.1 was assessed by luciferase assay. Recruitment of NKX3.1 to its cognate elements was monitored by Chromatin Immunoprecipitation assay. RESULTS: Comparative analysis of the TMPRSS2 promoter upstream sequences among different species revealed the conservation of binding sites for the androgen inducible NKX3.1 tumor suppressor. Defects of NKX3.1, such as, allelic loss, haploinsufficiency, attenuated expression or decreased protein stability represent established pathways in prostate tumorigenesis. We found that NKX3.1 directly binds to TMPRSS2 upstream sequences and negatively regulates the expression of the ERG protooncogene through the TMPRSS2-ERG gene fusion. CONCLUSIONS: These observations imply that the frequently noted loss-of-function of NKX3.1 cooperates with the activation of TMPRSS2-ERG fusions in prostate tumorigenesis.

A selective CutMix approach improves generalizability of deep learning-based grading and risk assessment of prostate cancer.

The Gleason score is an important predictor of prognosis in prostate cancer. However, its subjective nature can result in over- or under-grading. Our objective was to train an artificial intelligence (AI)-based algorithm to grade prostate cancer in specimens from patients who underwent radical prostatectomy (RP) and to assess the correlation of AI-estimated proportions of different Gleason patterns with biochemical recurrence-free survival (RFS), metastasis-free survival (MFS), and overall survival (OS). Training and validation of algorithms for cancer detection and grading were completed with three large datasets containing a total of 580 whole-mount prostate slides from 191 RP patients at two centers and 6218 annotated needle biopsy slides from the publicly available Prostate Cancer Grading Assessment dataset. A cancer detection model was trained using MobileNetV3 on 0.5 mm × 0.5 mm cancer areas (tiles) captured at 10× magnification. For cancer grading, a Gleason pattern detector was trained on tiles using a ResNet50 convolutional neural network and a selective CutMix training strategy involving a mixture of real and artificial examples. This strategy resulted in improved model generalizability in the test set compared with three different control experiments when evaluated on both needle biopsy slides and whole-mount prostate slides from different centers. In an additional test cohort of RP patients who were clinically followed over 30 years, quantitative Gleason pattern AI estimates achieved concordance indexes of 0.69, 0.72, and 0.64 for predicting RFS, MFS, and OS times, outperforming the control experiments and International Society of Urological Pathology system (ISUP) grading by pathologists. Finally, unsupervised clustering of test RP patient specimens into low-, medium-, and high-risk groups based on AI-estimated proportions of each Gleason pattern resulted in significantly improved RFS and MFS stratification compared with ISUP grading. In summary, deep learning-based quantitative Gleason scoring using a selective CutMix training strategy may improve prognostication after prostate cancer surgery.

Prostate cancer autoantibodies - applications in diagnosis, prognosis, monitoring disease progression and immunotherapy.

Although PSA testing is widely used in prostate cancer diagnosis, it remains an imperfect assay due to its lack of accuracy. While several urine or tissue-based gene expression assays are available to identify patients with higher risk of adverse disease and to aid in deciding treatment options, there is still a critical need for reliable biomarkers to monitor disease progression and treatment response. Autoantibodies (AAbs) produced by the humoral immune response against tumor associated antigens offer an attractive alternative, as they target a wide variety of prostate cancer specific antigens and can be collected by using clinically non-invasive methods. Herein, we review the transition from traditional methods that identify individual AAbs to high throughput approaches that detect multiple targets simultaneously in patient sera. We also discuss how these approaches improved the sensitivity and specificity of AAb detection and enhanced prostate cancer diagnosis and prognosis. Cancer vaccines offer potential as a novel therapeutic strategy in their ability to stimulate both cell-mediated and antibody-mediated cytotoxic responses. Ongoing efforts aim to identify immunotherapy targets that also stimulate a strong antibody response, since antibodies activated by the anti-cancer humoral response can eliminate cancer cells effectively via several distinct mechanisms. Autoantibodies are useful not only for the diagnosis of prostate cancer, predicting disease progression, and tracking response to treatment, but can also be harnessed as therapeutic agents for prostate cancer treatment.

Immunologic Assessment of Tumors from a Race-matched Military Cohort Identifies Mast Cell Depletion as a Marker of Prostate Cancer Progression.

Elucidating the cellular immune components underlying aggressive prostate cancer, especially among African American (AA) men who are disproportionately affected by this disease compared with Caucasian American (CA) men, will support more inclusive precision medicine treatment strategies. We aimed to evaluate which immune-related genes and cell types are differentially expressed in AA tumors and how immunobiology impacts prostate cancer progression. We purified nucleic acid from tumor biopsies, obtained following radical prostatectomy, from 51 patients (AA = 26, CA = 25). Gene expression was measured using the NanoString platform from which we estimated immune cell abundances and assessed differences between groups based on clinicopathologic data. Product-limit estimates determined associations with biochemical recurrence (BCR)-free and metastasis-free survival. DVL2 and KLRC2 were significantly upregulated in CA tumors and were also associated with worse disease progression. No significant differences in immune cell abundances by race were observed. Highly significant reductions in abundances of mast cells versus tumor-infiltrating lymphocytes (TIL) were found in men with high-grade pathologies and in men who later developed metastases. Low ratios of mast cells versus TILs were associated with worse BCR-free survival and metastasis-free survival. Although estimated immune cell abundances were not different by race, we identified genes involved in metabolism and natural killer cell functions that were differentially expressed between AA and CA tumors. Among the entire cohort, depletion of mast cells within prostatectomy tumors was characteristic of advanced disease and susceptibility to disease progression. Significance: Our findings demonstrate that there are immune-related genes and pathways that differ by race. Impaired intratumoral cellular immune composition, especially for TIL-normalized mast cells, may be vital in predicting and contributing to prostate cancer disease progression.

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.

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.

SUSP1 antagonizes formation of highly SUMO2/3-conjugated species.

Small ubiquitin-related modifier (SUMO) processing and deconjugation are mediated by sentrin-specific proteases/ubiquitin-like proteases (SENP/Ulps). We show that SUMO-specific protease 1 (SUSP1), a mammalian SENP/Ulp, localizes within the nucleoplasm. SUSP1 depletion within cell lines expressing enhanced green fluorescent protein (EGFP) fusions to individual SUMO paralogues caused redistribution of EGFP-SUMO2 and -SUMO3, particularly into promyelocytic leukemia (PML) bodies. Further analysis suggested that this change resulted primarily from a deficit of SUMO2/3-deconjugation activity. Under these circumstances, PML bodies became enlarged and increased in number. We did not observe a comparable redistribution of EGFP-SUMO1. We have investigated the specificity of SUSP1 using vinyl sulfone inhibitors and model substrates. We found that SUSP1 has a strong paralogue bias toward SUMO2/3 and that it acts preferentially on substrates containing three or more SUMO2/3 moieties. Together, our findings argue that SUSP1 may play a specialized role in dismantling highly conjugated SUMO2 and -3 species that is critical for PML body maintenance.

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.

SUMO-1 targets RanGAP1 to kinetochores and mitotic spindles.

RanGAP1 was the first documented substrate for conjugation with the ubiquitin-like protein SUMO-1. However, the functional significance of this conjugation has not been fully clarified. We sought to examine RanGAP1 behavior during mitosis. We found that RanGAP1 associates with mitotic spindles and that it is particularly concentrated at foci near kinetochores. Association with kinetochores appeared soon after nuclear envelope breakdown and persisted until late anaphase, but it was lost coincident with nuclear envelope assembly in telophase. A mutant RanGAP1 protein lacking the capacity to be conjugated to SUMO-1 no longer associated with spindles, indicating that conjugation was essential for RanGAP1's mitotic localization. RanBP2, a nuclear pore protein that binds SUMO-1-conjugated RanGAP1 during interphase, colocalized with RanGAP1 on spindles, suggesting that a complex between these two proteins may be involved in mitotic targeting of RanGAP1. This report shows for the first time that SUMO-1 conjugation is required for mitotic localization of RanGAP1, and suggests that a major role of SUMO-1 conjugation to RanGAP1 may be the spatial regulation of the Ran pathway during mitosis.

Androgen-regulated and highly tumorigenic human prostate cancer cell line established from a transplantable primary CWR22 tumor.

PURPOSE: One of the major obstacles in understanding the molecular mechanisms underlying the transition of prostate cancer growth from androgen dependency to a hormone-refractory state is the lack of androgen-regulated and tumorigenic human prostate cancer cell lines. EXPERIMENTAL DESIGN: We have established and characterized a new human prostate cancer cell line, CWR22Pc, derived from the primary CWR22 human prostate xenograft tumors. RESULTS: The growth of CWR22Pc cells is induced markedly by dihydrotestosterone, and CWR22Pc cells express high levels of androgen receptor (AR) and prostate-specific antigen (PSA). Importantly, PSA expression in CWR22Pc cells is regulated by androgens. Stat5a/b, Stat3, Akt, and mitogen-activated protein kinase were constitutively active or cytokine inducible in CWR22Pc cells. The AR in CWR22Pc cells contains the H874Y mutation, but not the exon 3 duplication or other mutations. When inoculated subcutaneously into dihydrotestosterone-supplemented castrated nude mice, large tumors formed rapidly in 20 of 20 mice, whereas no tumors developed in mice without circulating dihydrotestosterone. Moreover, the serum PSA levels correlated with the tumor volumes. When androgens were withdrawn from the CWR22Pc tumors grown in nude mice, the tumors initially shrank but regrew back as androgen-independent tumors. CONCLUSIONS: This androgen-regulated and tumorigenic human prostate cancer cell line provides a valuable tool for studies on androgen regulation of prostate cancer cells and on the molecular mechanisms taking place in growth promotion of prostate cancer when androgens are withdrawn from the growth environment. CWR22Pc cells also provide a model system for studies on the regulation of transcriptional activity of mutated H874YAR in a prostate cancer cell context.

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.

Signal transducer and activator of transcription 5A/B in prostate and breast cancers.

Protein kinase signaling pathways, such as Janus kinase 2-Signal transducer and activator of transcription 5A/B (JAK2-STAT5A/B), are of significant interest in the search for new therapeutic strategies in both breast and prostate cancers. In prostate cancer, the components of the JAK2-STAT5A/B signaling pathway provide molecular targets for small-molecule inhibition of survival and growth signals of the cells. At the same time, new evidence suggests that the STAT5A/B signaling pathway is involved in the transition of organ-confined prostate cancer to hormone-refractory disease. This implies that the active JAK2-STAT5A/B signaling pathway potentially provides the means for pharmacological intervention of clinical prostate cancer progression. In addition, active STAT5A/B may serve as a prognostic marker for identification of those primary prostate cancers that are likely to progress to aggressive disease. In breast cancer, the role of STAT5A/B is more complex. STAT5A/B may have a dual role in the regulation of malignant mammary epithelium. Data accumulated from mouse models of breast cancer suggest that in early stages of breast cancer STAT5A/B may promote malignant transformation and enhance growth of the tumor. This is in contrast to established breast cancer, where STAT5A/B may mediate the critical cues for maintaining the differentiation of mammary epithelium. In addition, present data suggest that activation of STAT5A/B in breast cancer predicts favorable clinical outcome. The dual nature of STAT5A/B action in breast cancer makes the therapeutic use of STAT5 A/B more complex.

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

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

Erratum: ETS Related Gene mediated Androgen Receptor Aggregation and Endoplasmic Reticulum Stress in Prostate Cancer Development.

A correction to this article has been published and is linked from the HTML version of this paper. The error has not been fixed in the paper.

ETS Related Gene mediated Androgen Receptor Aggregation and Endoplasmic Reticulum Stress in Prostate Cancer Development.

Mechanistic studies of deregulated ERG in prostate cancer and other cancers continue to enhance its role in cancer biology and its utility as a biomarker and therapeutic target. Here, we show that ERG, through its physical interaction with androgen receptor, induces AR aggregation and endoplasmic reticulum stress in the prostate glands of ERG transgenic mice. Histomorphological alterations and the expression of ER stress sensors Atf6, Ire1α, Perk, their downstream effectors Grp78/BiP and eIF2α in ERG transgenic mouse prostate glands indicate the presence of chronic ER stress. Transient activation of apoptotic cell death during early age correlated well with the differential regulation of ER stress sensors, in particular Perk. Epithelial cells derived from ERG transgenic mouse prostates have increased prostasphere formation with resistance to radiation induced cell death. Continued activation of cell survival factors, Atf6 and Ire1α during chronic ER stress due to presence of ERG in prostate epithelium induces survival pathways and provides a selection pressure in the continuum of ERG dependent neoplastic process. These novel insights will enhance the understanding of the mechanistic functions of ERG in prostate tumor biology and towards development of early targeted therapeutic strategies for prostate cancer.