Long noncoding RNA MIR31HG exhibits oncogenic property in pancreatic ductal adenocarcinoma and is negatively regulated by miR-193b

Long noncoding RNAs (lncRNAs) play important regulatory roles in a variety of diseases, including many tumors. However, the functional roles of these transcripts and mechanisms responsible for their deregulation in pancreatic ductal adenocarcinoma (PDAC) are not thoroughly understood. In this study, we discovered that lncRNA MIR31HG is markedly upregulated in PDAC. Knockdown of MIR31HG significantly suppressed PDAC cell growth, induced apoptosis and G1/S arrest, and inhibited invasion, whereas enhanced expression of MIR31HG had the opposite effects. Online database analysis tools showed that miR-193b could target MIR31HG and we found an inverse correlation between MIR31HG and miR-193b in PDAC specimens. Inhibition of miR-193b expression significantly upregulated the MIR31HG level, while overexpression of miR-193b suppressed MIR31HG's expression and function, suggesting that MIR31HG is negatively regulated by miR-193b. Moreover, using luciferase reporter and RIP assays, we provide evidence that miR-193b directly targeted MIR31HG by binding to two microRNA binding sites in the MIR31HG sequence. On the other hand, MIR31HG may act as an endogenous ‘sponge' by competing for miR-193b binding to regulate the miRNA targets. Collectively, these results demonstrate that MIR31HG functions as an oncogenic lncRNA that promotes tumor progression, and miR-193b targets not only protein-coding genes but also the lncRNA, MIR31HG.