Neuroendocrine prostate cancer (NEPC), a lethal form of the disease, is characterized by loss of androgen receptor (AR) signaling during neuroendocrine transdifferentiation, which results in resistance to AR-targeted therapy. Clinically, genomically and epigenetically, NEPC resembles other types of poorly differentiated neuroendocrine tumors (NETs). Through pan-NET analyses, we identified ONECUT2 as a candidate master transcriptional regulator of poorly differentiated NETs. ONECUT2 ectopic expression in prostate adenocarcinoma synergizes with hypoxia to suppress androgen signaling and induce neuroendocrine plasticity. ONEUCT2 drives tumor aggressiveness in NEPC, partially through regulating hypoxia signaling and tumor hypoxia. Specifically, ONECUT2 activates SMAD3, which regulates hypoxia signaling through modulating HIF1α chromatin-binding, leading NEPC to exhibit higher degrees of hypoxia compared to prostate adenocarcinomas. Treatment with hypoxia-activated prodrug TH-302 potently reduces NEPC tumor growth. Collectively, these results highlight the synergy between ONECUT2 and hypoxia in driving NEPC, and emphasize the potential of hypoxia-directed therapy for NEPC patients.

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...

KLF5 possesses both tumor suppressing and tumor promoting activities, though the mechanism controlling these opposing functions is unknown. In cultured non-cancerous epithelial cells, KLF5 converts from pro-proliferative to anti-proliferative activity upon TGFβ-induced acetylation, which sequentially alters the KLF5 transcriptional complex and the expression of genes such as p15 and MYC. In this study, we tested whether the acetylation status of KLF5 also determines its opposing functions in tumorigenesis using the PC-3 and DU 145 prostate cancer cell lines, whose proliferation is inhibited by TGFβ. KLF5 inhibited the proliferation of these cancer cells, and the inhibition was dependent on KLF5 acetylation. MYC and p15 showed the same patterns of expression change found in non-cancerous cells. In nude mice, KLF5 also suppressed tumor growth in an acetylation-dependent manner. Furthermore, deacetylation switched KLF5 to tumor promoting activity, and blocking TGFβ signaling attenuated the tumor suppressor activity of KLF5. RNA-Seq and comprehensive data analysis suggest that multiple molecules, including RELA, p53, CREB1, MYC, JUN, ER, AR and SP1, mediate the opposing functions of AcKLF5 and unAcKLF5. These results provide novel insights into the mechanism by which KLF5 switches from anti-tumorigenic to pro-tumorigenic function, and also suggest the roles of AcKLF5 and unAcKLF5, respectively, in the tumor suppressing and tumor promoting functions of TGFβ.