Abstract
BACKGROUND: Prostate cancer (PC) is common male cancer with high mortality worldwide. Emerging evidence demonstrated that long noncoding RNAs (lncRNAs) play critical roles in various type of cancers including PC by serving as competing endogenous RNAs (ceRNAs) to modulate microRNAs (miRNAs). LncRNA activated by DNA damage (NORAD) was found to be upregulated in PC cells, while the detailed function and regulatory mechanism of NORAD in PC progression remains largely unclear. METHODS: Expression of NORAD in PC tissues and cell lines were detected by real-time quantitative PCR (qRT-PCR). NORAD was respectively overexpressed and knocked down by transfection with pcDNA-NORAD and NORAD siRNA into PC-3 and LNCap cells. Cell proliferation, invasion and apoptosis were determined by using CCK-8, Transwell and Flow cytometry assays, respectively. The target correlations between miR-30-5p and NORAD or RAB11A were confirmed by using dual luciferase reporter assay. Moreover, expression levels of RAB11A, the epithelial-mesenchymal transition (EMT) marker proteins and the Wnt pathway related proteins were measured by Western blotting. Tumor xenograft assay was used to study the effect of NORAD on tumor growth in vivo. RESULTS: NORAD was upregulated in PC tissues and cells. Overexpression of NORAD promoted cell proliferation, invasion, EMT, and inhibited cell apoptosis; while knockdown of NORAD had the opposite effect. NORAD was found to be functioned as a ceRNA to bind and downregulated miR-30a-5p that was downregulated in PC tumor tissues. Rescue experiments revealed that miR-30a-5p could weaken the NORAD-mediated promoting effects on cell proliferation, invasion and EMT. Furthermore, RAB11A that belongs to a member of RAS oncogene family was verified as a target of miR-30a-5p, and reintroduction of RAB11A attenuated the effects of miR-30a-5p overexpression on cell proliferation, invasion, EMT and apoptosis of PC cells. More importantly, silencing RAB11A partially reversed the promoting effects of NORAD overexpression on cell proliferation, invasion and EMT of PC cells via the WNT/β-catenin pathway. Lastly, tumorigenicity assay in vivo demonstrated that NORAD increased tumor volume and weight via miR-30a-5p /RAB11A pathway. CONCLUSION: Our results indicated a significant role of NORAD in mechanisms associated with PC progression. NORAD promoted cell proliferation, invasion and EMT via the miR-30a-5p/RAB11A/WNT/β-catenin pathway, thus inducing PC tumor growth.