The long non-coding RNA <i>HORAS5</i> mediates castration-resistant prostate cancer survival by activating the androgen receptor transcriptional program

Prostate Cancer (PCa) is driven by the androgen receptor (AR)-signaling axis. Hormonal therapy often mitigates PCa progression, but a notable number of cases progress to castration-resistant PCa (CRPC). CRPC retains AR-activity and is incurable. Long non-coding RNAs (lncRNAs) represent an uncharted region of the transcriptome. Several lncRNAs have been recently described to mediate oncogenic functions, suggesting that these molecules can be potential therapeutic targets. Here, we identified CRPC-associated lncRNAs by analyzing patient-derived xenografts (PDXs) and clinical data. Subsequently, we characterized one of the CRPC-promoting lncRNAs, HORAS5, in vitro and in vivo. We demonstrated that HORAS5 is a stable, cytoplasmic lncRNA that promotes CRPC proliferation and survival by maintaining AR activity under androgen-depleted conditions. Most strikingly, knockdown of HORAS5 causes a significant reduction in the expression of AR itself and oncogenic AR targets such as KIAA0101. Elevated expression of HORAS5 is also associated with worse clinical outcomes in patients. Our results from HORAS5 inhibition in in vivo models further confirm that HORAS5 is a viable therapeutic target for CRPC. Thus, we posit that HORAS5 is a novel, targetable mediator of CRPC through its essential role in the maintenance of oncogenic AR activity. Overall, this study adds to our mechanistic understanding of how lncRNAs function in cancer progression

Identification of a long non-coding RNA as a novel biomarker and potential therapeutic target for metastatic prostate cancer

Metastatic prostate cancer (PCa) is still an incurable disease. Long non-coding RNAs (lncRNAs) may be an overlooked source of cancer biomarkers and therapeutic targets. We therefore performed RNA sequencing on paired metastatic/non-metastatic PCa xenografts derived from clinical specimens. The most highly up-regulated transcript was LOC728606, a lncRNA now designated PCAT18. PCAT18 is specifically expressed in the prostate compared to 11 other normal tissues (p-4, odds ratio>2). The PES was significantly associated with androgen receptor (AR) signalling. Accordingly, AR activation dramatically up-regulated PCAT18 expression in vitro and in vivo. PCAT18 silencing significantly (p<0.001) inhibited PCa cell proliferation and triggered caspase 3/7 activation, with no effect on non-neoplastic cells. PCAT18 silencing also inhibited PCa cell migration (p<0.01) and invasion (p<0.01). These results position PCAT18 as a potential therapeutic target and biomarker for metastatic PCa

Integrated analysis of the prostate cancer small-nucleolar transcriptome reveals <i>SNORA55</i> as a driver of prostate cancer progression

Metastasis is the primary cause of death in prostate cancer (PCa) patients. Small nucleolar RNAs (snoRNAs) have long been considered "housekeeping" genes with no relevance for cancer biology. Emerging evidence has challenged this assumption, suggesting that snoRNA expression is frequently modulated during cancer progression. Despite this, no study has systematically addressed the prognostic and functional significance of snoRNAs in PCa. We performed RNA Sequencing on paired metastatic/non-metastatic PCa xenografts derived from clinical specimens. The clinical significance of differentially expressed snoRNAs was further investigated in two independent primary PCa cohorts (131 and 43 patients, respectively). The snoRNA demonstrating the strongest association with clinical outcome was quantified in PCa patient-derived serum samples and its functional relevance was investigated in PCa cells via gene expression profiling, pathway analysis and gene silencing. Our comparison revealed 21 differentially expressed snoRNAs in the metastatic vs. non-metastatic xenografts. Of those, 12 were represented in clinical databases and were further analyzed. SNORA55 emerged as a predictor of shorter relapse-free survival (results confirmed in two independent databases). SNORA55 was reproducibly detectable in serum samples from PCa patients. SNORA55 silencing in PCa cell lines significantly inhibited cell proliferation and migration. Pathway analysis revealed that SNORA55 expression is significantly associated with growth factor signaling and pro-inflammatory cytokine expression in PCa. Our results demonstrate that SNORA55 up-regulation predicts PCa progression and that silencing this non-coding gene affects PCa cell proliferation and metastatic potential, thus positioning it as both a novel biomarker and therapeutic target

CDK12 loss drives prostate cancer progression, transcription-replication conflicts, and synthetic lethality with paralog CDK13.

Biallelic loss of cyclin-dependent kinase 12 (CDK12) defines a metastatic castration-resistant prostate cancer (mCRPC) subtype. It remains unclear, however, whether CDK12 loss drives prostate cancer (PCa) development or uncovers pharmacologic vulnerabilities. Here, we show Cdk12 ablation in murine prostate epithelium is sufficient to induce preneoplastic lesions with lymphocytic infiltration. In allograft-based CRISPR screening, Cdk12 loss associates positively with Trp53 inactivation but negatively with Pten inactivation. Moreover, concurrent Cdk12/Trp53 ablation promotes proliferation of prostate-derived organoids, while Cdk12 knockout in Pten-null mice abrogates prostate tumor growth. In syngeneic systems, Cdk12/Trp53-null allografts exhibit luminal morphology and immune checkpoint blockade sensitivity. Mechanistically, Cdk12 inactivation mediates genomic instability by inducing transcription-replication conflicts. Strikingly, CDK12-mutant organoids and patient-derived xenografts are sensitive to inhibition or degradation of the paralog kinase, CDK13. We therein establish CDK12 as a bona fide tumor suppressor, mechanistically define how CDK12 inactivation causes genomic instability, and advance a therapeutic strategy for CDK12-mutant mCRPC

The evolutionarily conserved long non‐coding RNA <i>LINC00261</i> drives neuroendocrine prostate cancer proliferation and metastasis <i>via</i> distinct nuclear and cytoplasmic mechanisms

Metastatic neuroendocrine prostate cancer (NEPC) is a highly aggressive disease, whose incidence is rising. Long noncoding RNAs (lncRNAs) represent a large family of disease- and tissue-specific transcripts, most of which are still functionally uncharacterized. Thus, we set out to identify the highly conserved lncRNAs that play a central role in NEPC pathogenesis. To this end, we performed transcriptomic analyses of donor-matched patient-derived xenograft models (PDXs) with immunohistologic features of prostate adenocarcinoma (AR+/PSA+) or NEPC (AR-/SYN+/CHGA+ ) and through differential expression analyses identified lncRNAs that were upregulated upon neuroendocrine transdifferentiation. These genes were prioritized for functional assessment based on the level of conservation in vertebrates. Here, LINC00261 emerged as the top gene with over 3229-fold upregulation in NEPC. Consistently, LINC00261 expression was significantly upregulated in NEPC specimens in multiple patient cohorts. Knockdown of LINC00261 in PC-3 cells dramatically attenuated its proliferative and metastatic abilities, which are explained by parallel downregulation of CBX2 and FOXA2 through distinct molecular mechanisms. In the cell cytoplasm, LINC00261 binds to and sequesters miR-8485 from targeting the CBX2 mRNA, while inside the nucleus, LINC00261 functions as a transcriptional scaffold to induce SMAD-driven expression of the FOXA2 gene. For the first time, these results demonstrate hyperactivation of the LINC00261-CBX2-FOXA2 axes in NEPC to drive proliferation and metastasis, and that LINC00261 may be utilized as a therapeutic target and a biomarker for this incurable disease

The non-coding transcriptome as a dynamic regulator of cancer metastasis.

Since the discovery of microRNAs, non-coding RNAs (NC-RNAs) have increasingly attracted the attention of cancer investigators. Two classes of NC-RNAs are emerging as putative metastasis-related genes: long non-coding RNAs (lncRNAs) and small nucleolar RNAs (snoRNAs). LncRNAs orchestrate metastatic progression through several mechanisms, including the interaction with epigenetic effectors, splicing control and generation of microRNA-like molecules. In contrast, snoRNAs have been long considered "housekeeping" genes with no relevant function in cancer. However, recent evidence challenges this assumption, indicating that some snoRNAs are deregulated in cancer cells and may play a specific role in metastasis. Interestingly, snoRNAs and lncRNAs share several mechanisms of action, and might synergize with protein-coding genes to generate a specific cellular phenotype. This evidence suggests that the current paradigm of metastatic progression is incomplete. We propose that NC-RNAs are organized in complex interactive networks which orchestrate cellular phenotypic plasticity. Since plasticity is critical for cancer cell metastasis, we suggest that a molecular interactome composed by both NC-RNAs and proteins orchestrates cancer metastasis. Interestingly, expression of lncRNAs and snoRNAs can be detected in biological fluids, making them potentially useful biomarkers. NC-RNA expression profiles in human neoplasms have been associated with patients' prognosis. SnoRNA and lncRNA silencing in pre-clinical models leads to cancer cell death and/or metastasis prevention, suggesting they can be investigated as novel therapeutic targets. Based on the literature to date, we critically discuss how the NC-RNA interactome can be explored and manipulated to generate more effective diagnostic, prognostic, and therapeutic strategies for metastatic neoplasms

Abstract 3347: Exploring the role of ASXL family of genes in enabling oncogenic AR-signaling in prostate cancer

Abstract Prostate cancer (PCa) is the second leading cause of cancer-related mortality in North American men. In recent years, there has been mounting evidence establishing the centrality of epigenetic mechanisms in PCa initiation and progression. Accordingly, various epigenetic genes have been described to collaborate with the androgen receptor (AR) in enabling its oncogenic transcriptional program and aberrantly restoring its activity in metastatic castration resistant PCa (mCRPC). Concordantly, our lab has recently described two epigenetic genes, BRD4 &amp; MLL2, as key co-activators of the AR signaling complex. Furthermore, we have demonstrated the therapeutic benefits of inhibiting the activity of these genes in advanced PCa. Thus, in a setting where invariably all metastatic PCa patients progress to evolve resistance to anti-AR therapy, epigenetic genes emerge as potent co-targets with the promise to improve patient outcomes. To To identify novel AR-collaborating genes, as part of a multi-institutional consortium, our lab had performed comprehensive molecular profiling of 150 mCRPC patient tumors. This study revealed multiple genetic aberrations in chromatin modifier genes. Interestingly, this list comprised of recurrent mutations in the ASXL family of genes in about ~5% of the cases. ASXL family members are epigenetic scaffolding proteins that assemble chromatin modifiers and transcription factors to specific genomic loci with histone modifications. Although intricately involved in the genesis of acute myeloid leukemia, hitherto, no study has comprehensively described the role of ASXL genes in PCa biology. Two members of this family, ASXL1 and ASXL2, are robustly expressed in PCa. Co-immunoprecipitation assays revealed that these proteins also reside in the AR-signaling complex. Notably, siRNA-mediated inhibition of these genes dramatically attenuated proliferation of AR-dependent PCa cells, but had minimal effect on non-neoplastic prostate cells. These preliminary results strongly implicate ASXL genes in the oncogenic re-programming of AR-activity and warrant further investigation towards exploring of their therapeutic value in currently incurable mCRPC. Citation Format: Abhijit Parolia, Xuhong Cao, Arul Chinnaiyan. Exploring the role of ASXL family of genes in enabling oncogenic AR-signaling in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3347. doi:10.1158/1538-7445.AM2017-3347</jats:p

Non-invasive metabolic imaging of brain tumours in the era of precision medicine

The genomic revolution in cancer has uncovered a variety of mutations in primary brain tumors. This has created an urgent need to develop non-invasive imaging biomarkers to assess and integrate this genetic information in the clinical management of patients. Metabolic reprogramming is a central hallmark of cancers including brain tumors. Many of the molecular pathways implicated in brain tumors directly reprogram metabolism. This provides the opportunity to devise in vivo metabolism-based imaging modalities for patient stratification, to improve diagnosis, and to monitor treatment response. Metabolic phenomena like the Warburg effect and altered mitochondrial metabolism can be leveraged to image brain tumors using techniques like positron emission tomography (PET) imaging and Magnetic Resonance (MR) metabolic imaging. Moreover, genetic alterations such as isocitrate dehydrogenase mutations produced unique metabolic signatures that can be detected using MR spectroscopy. There is a growing need to translate our understanding of the molecular aspects of brain tumors to in vivo imaging in patients. Metabolism-based imaging provides a unique platform to achieve this. In this review we examine the molecular basis for metabolic reprograming in brain tumors and examine current non-invasive metabolic imaging strategies to interrogate them, for the ultimate goal of guiding and improving patient care