Castration-resistant prostate cancer (CRPC) that occurs after the failure of androgen deprivation therapy is the leading cause of deaths in prostate cancer patients. Thus, there is an obvious and urgent need to fully understand the mechanism of CRPC and discover novel therapeutic targets. Long noncoding RNAs (lncRNAs) are crucial regulators in many human cancers, yet their potential roles and molecular mechanisms in CRPC are poorly understood. In this study, we discovered that an lncRNA HOXD-AS1 is highly expressed in CRPC cells and correlated closely with Gleason score, T stage, lymph nodes metastasis, and progression-free survival. Knockdown of HOXD-AS1 inhibited the proliferation and chemo-resistance of CRPC cells in vitro and in vivo. Furthermore, we identified several cell cycle, chemo-resistance, and castration-resistance-related genes, including PLK1, AURKA, CDC25C, FOXM1, and UBE2C, that were activated transcriptionally by HOXD-AS1. Further investigation revealed that HOXD-AS1 recruited WDR5 to directly regulate the expression of target genes by mediating histone H3 lysine 4 tri-methylation (H3K4me3). In conclusion, our findings indicate that HOXD-AS1 promotes proliferation, castration resistance, and chemo-resistance in prostate cancer by recruiting WDR5. This sheds a new insight into the regulation of CRPC by lncRNA and provides a potential approach for the treatment of CRPC.

Purpose: Chemoresistance and tumor relapse are the leading cause of deaths in bladder cancer patients. Bladder cancer stem cells (BCSCs) have been reported to contribute to these pathologic properties. However, the molecular mechanisms underlying their self-renewal and chemoresistance remain largely unknown. In the current study, a novel lncRNA termed Low expressed in Bladder Cancer Stem cells (lnc-LBCS) has been identified and explored in BCSCs.Experimental Design: Firstly, we establish BCSCs model and explore the BCSCs-associated lncRNAs by transcriptome microarray. The expression and clinical features of lnc-LBCS are analyzed in three independent large-scale cohorts. The functional role and mechanism of lnc-LBCS are further investigated by gain-and loss-of-function assays in vitro and in vivo.Results: Lnc-LBCS is significantly downregulated in BCSCs and cancer tissues, and correlates with tumor grade, chemo-therapy response, and prognosis. Moreover, lnc-LBCS markedly inhibits self-renewal, chemoresistance, and tumor initiation of BCSCs both in vitro and in vivo. Mechanistically, lnc-LBCS directly binds to heterogeneous nuclear ribonucleoprotein K (hnRNPK) and enhancer of zeste homolog 2 (EZH2), and serves as a scaffold to induce the formation of this complex to repress SRY-box 2 (SOX2) transcription via mediating histone H3 lysine 27 tri-methylation. SOX2 is essential for self-renewal and chemoresistance of BCSCs, and correlates with the clinical severity and prognosis of bladder cancer patients.Conclusions: As a novel regulator, lnc-LBCS plays an important tumor-suppressor role in BCSCs' self-renewal and chemoresistance, contributing to weak tumorigenesis and enhanced chemosensitivity. The lnc-LBCS-hnRNPK-EZH2-SOX2 regulatory axis may represent a therapeutic target for clinical intervention in chemoresistant bladder cancer.

WD repeat domain 5 (WDR5) plays an important role in various biological functions through the epigenetic regulation of gene transcription; however, its role in bladder cancer remains largely unknown. Our study investigated the role of WDR5 in bladder cancer and demonstrated that WDR5 was upregulated in bladder cancer tissues, and elevated WDR5 protein levels positively correlated with advanced tumor stage and poor survival. Through gain or loss of function, we demonstrated that WDR5 promoted proliferation, self-renewal and chemoresistance to cisplatin in bladder cancer cells in vitro, and tumor growth in vivo. Mechanistically, WDR5 regulated various functions in bladder cancer by mediating the transcription of cyclin B1, cyclin E1, cyclin E2, UHMK1, MCL1, BIRC3 and Nanog by histone H3 lysine 4 trimethylation. Therefore, we have discovered that WDR5 plays an important role in bladder cancer suggesting that WDR5 is a potential biomarker and a promising target in the treatment of bladder cancer.