Neuroendocrine prostate cancer (NEPC) is the most lethal prostatic neoplasm.NEPC is thought to originate from the trans-differentiation of AR-positive adenocarcinoma cells. We have previously shown that an epigenetic/non-coding interactome (ENI) orchestrates cancer cells' plasticity, thereby allowing the emergence of metastatic, drugresistant neoplasms. The primary objective of this manuscript is to discuss evidence indicating that some components of the ENI (Polycomb genes, microRNAs) play a key role in NEPC initiation and progression. Long non-coding RNAs (lncRNAs) represent vast and largely unexplored component of the ENI. Their role in NEPC has not been investigated. We show preliminary evidence indicating that a lncRNA (MIAT) is selectively up-regulated in NEPCs and might interact with Polycomb genes. Our results indicate that lncRNAs can be exploited as new biomarkers and therapeutic targets for NEPC.Keywords: Neuroendocrine prostate cancer; MIAT; Long non-coding RNAs; Polycomb; Epigenetic/non-coding interactome; Trans-differentiation. Neuroendocrine Prostate Cancer: Clinical and Molecular FeaturesIn adult males, the prostate is a small acorn-shaped tissue with ductal-acinar histology surrounding the urethra at the base of the bladder. Its main function is to contribute secretory proteins to the seminal fluid [1]. The adult prostate is a pseudo-stratified epithelium composed of three main cell lineages (Fig.1, left panel): 1) secretory luminal cells are the predominant cell type; these cells express keratins (K8, K18), the androgen receptor (AR) and secretory proteins such as prostate-specific antigen (PSA) and prostatic specific acid phosphatase (PSAP);2) basal cells expressing K5 and K14 keratins and p63 are the second major cell type;3) neuroendocrine cells (NEC) expressing chromogranin A (CHGA), synaptophysin (SYP), and neuropeptides are scattered throughout the basal layer and comprise less than 1% of normal prostatic glandular epithelium [1][2][3].Prostate cancer (PCa) represents the second most frequently diagnosed neoplasm and is the sixth leading cause of cancer-related deaths in males worldwide [4,5]. In keeping with the composition of prostate epithelium, more than 95% of PCas are classified as adenocarcinomas, which show luminal phenotype and AR expression [6] (Fig.1, middle panel).Endogenous androgens, mainly produced by the testis, bind to the AR and fuel prostate adenocarcinoma proliferation [7]. For this reason, androgen-deprivation therapy (a.k.a. castration) is an effective therapeutic strategy for this disease. However, patients invariably relapse despite castrate androgen levels (castration-resistant PCa, CRPC) mainly via genetic and epigenetic alterations that facilitate ligand-independent AR activation, amplify the ARdependent signaling, or trigger different proliferative pathways [7]. CRPCs are characterized by substantially worse prognoses, but chemotherapeutics and newly approved hormonal treatments (e.g., Enzalutamide [8] and Abiraterone [9]) are still effective in p...

Carcinoma of the prostate is the most common cancer in men. Treatment of aggressive prostate cancer involves a regiment of radical prostectomy, radiation therapy, chemotherapy and hormonal therapy. Despite significant improvements in the last decade, the treatment of prostate cancer remains unsatisfactory, because a significant fraction of prostate cancers develop resistance to multiple treatments and become incurable. This prompts an urgent need to investigate the molecular mechanisms underlying the evolution of therapy-induced resistance of prostate cancer either in the form of castration-resistant prostate cancer (CRPC) or transdifferentiated neuroendocrine prostate cancer (NEPC). By analyzing micro-RNA expression profiles in a set of patient-derived prostate cancer xenograft tumor lines, we identified miR-100-5p as one of the key molecular components in the initiation and evolution of androgen ablation therapy resistance in prostate cancer. In vitro results showed that miR-100-5p is required for hormone-independent survival and proliferation of prostate cancer cells post androgen ablation. In Silico target predictions revealed that miR-100-5p target genes are involved in key aspects of cancer progression, and are associated with clinical outcome. Our results suggest that mir-100-5p is a possible therapeutic target involved in prostate cancer progression and relapse post androgen ablation therapy.

Prostate cancer ( PC a) is driven by the androgen receptor ( AR )‐signaling axis. Hormonal therapy often mitigates PC a progression, but a notable number of cases progress to castration‐resistant PC a ( CRPC ). CRPC retains AR activity and is incurable. Long noncoding RNA (lnc RNA ) represent an uncharted region of the transcriptome. Several lnc RNA have been recently described to mediate oncogenic functions, suggesting that these molecules can be potential therapeutic targets. Here, we identified CRPC ‐associated lnc RNA by analyzing patient‐derived xenografts ( PDX s) and clinical data. Subsequently, we characterized one of the CRPC ‐promoting lnc RNA , HORAS 5 , in vitro and in vivo . We demonstrated that HORAS 5 is a stable, cytoplasmic lnc RNA that promotes CRPC proliferation and survival by maintaining AR activity under androgen‐depleted conditions. Most strikingly, knockdown of HORAS 5 causes a significant reduction in the expression of AR itself and oncogenic AR targets such as KIAA 0101. Elevated expression of HORAS 5 is also associated with worse clinical outcomes in patients. Our results from HORAS 5 inhibition in in vivo models further confirm that HORAS 5 is a viable therapeutic target for CRPC . Thus, we posit that HORAS 5 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 lnc RNA function in cancer progression.

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 À /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

Background Androgen deprivation therapy (ADT) is the treatment of choice for metastatic prostate cancer (PCa). After an initial response to ADT, PCa cells can generate castration resistant (CRPC) or neuroendocrine (NEPC) malignancies, which are incurable. T‐type calcium channels (TTCCs) are emerging as promising therapeutic targets for several cancers, but their role in PCa progression has never been investigated. Methods To examine the role of TTCCs in PCa, we analyzed their expression level, copy number variants (CNV) and prognostic significance using clinical datasets (Oncomine and cBioPortal). We then evaluated TTCC expression in a panel of PCa cell lines and measured the effect of their inhibition on cell proliferation and survival using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) and caspase assays. Results TTCCs were upregulated in PCas harboring androgen receptor (AR) mutations; CNV rate was positively associated with PCa progression. Higher expression of one TTCC isoform (CACNA1G) predicted poorer postoperative prognosis in early stage PCa samples. Pharmacological or small interfering RNA (siRNA)‐based inhibition of TTCCs caused a decrease in PC‐3 cell survival and proliferation. Conclusions Our results show that TTCCs are overexpressed in advanced forms of PCa and correlate with a poorer prognosis. TTCC inhibition reduces cell proliferation and survival, suggesting that there may be possible value in the therapeutic targeting of TTCCs in advanced PCa.