Long noncoding RNA NORAD regulates cancer cell proliferation and migration in human osteosarcoma by endogenously competing with miR-199a-3p

In this study, we evaluated the expressions and functions of a long noncoding RNA (lncRNA), Noncoding RNA activated by DNA damage (NORAD) in human osteosarcoma. NORAD expressions were evaluated by qRT-PCR in in vitro osteosarcoma cell lines and in vivo clinical specimens. SiRNA-induced NORAD downregulation was conducted in Saos-2 and 143B cells, and the functional effects of NORAD downregulation on osteosarcoma cells were evaluated by CCK-8 proliferation assay, 24-well transwell invasion assay and in vivo tumor explant assay, respectively. The possibility of NORAD endogenously competing microRNA target, hsa-miR-199a-3p was examined by dual-luciferase reporter assay and qRT-PCR. Then, hsa-miR-199a-3p was downregulated in NORAD-inhibited osteosarcoma cells to examine its role in regulating NORAD inhibition induced cancer suppression in osteosarcoma cells. NORAD was found to be significantly overexpressed in both osteosarcoma cells and osteosarcoma tumors. In Saos-2 and 143B cells transfected with NORAD-specific siRNA, their proliferation, invasion, and in vivo explant growth were all markedly suppressed. Hsa-miR-199a-3p was confirmed to be the competing target of NORAD. Its downregulation in Saos-2 and 143B cells inversely augment proliferation and invasion that were initially suppressed by NORAD-downregulation. The results of our study show that NORAD plays an important role in regulating cancer cell functions of osteosarcoma, possibly through endogenously competing with hsa-miR-199a-3p.