lncRNA NORAD promotes the progression of osteosarcoma via targeting of miR-155-5p

Osteosarcoma (OS) is the most common malignant bone tumor in teens. Non-coding RNA activated by DNA damage (NORAD), a long non-coding RNA (lncRNA), has been reported to be involved in cancer biology, although its role in OS remains largely unknown. In the present study reverse transcription-quantitative PCR (RT-qPCR) was used to determine the expression levels of NORAD and miR-155-5p in samples from patients with OS. OS cell lines (Saos-2 and U2OS) were used as cell models. The biological influence of NORAD on OS cells was studied in vitro using Cell Counting Kit-8 and Transwell assays. The interaction between NORAD and miR-155-5p was clarified by bioinformatics analysis, RT-qPCR, luciferase reporter assay and RNA immunoprecipitation. NORAD was significantly increased in OS samples in comparison with controls, while miR-155-5p was reduced. Knockdown of NORAD and transfection of miR-155-5p mimics markedly inhibited the viability, migration and invasion of OS cells. There was a negative correlation between NORAD and miR-155-5p expression levels in OS samples. Taken together, the results of the present study indicated that the NORAD/miR-155-5p axis played a crucial role in regulating the proliferation, migration and invasion of OS cells. It is hypothesized that NORAD and miR-155-5p may serve as potential novel therapeutic targets for OS management.