Long non-coding RNA DANCR facilitates glioma malignancy by sponging miR-33a-5p

Glioma is one of the most fatal brain tumors and it is characterized by rapid progression, high malignancy and early metastasis. Deregulation of 'long non-coding RNA differentiation antagonizing non-protein coding RNA' (LncRNA DANCR) is associated with the development, progression and metastasis of various cancers. Herein, we investigated LncRNA DANCR's functional role in glioma malignancy, and results showed that LncRNA DANCR was increased in glioma tissues and cells compared to normal brain tissues and cells, and that its expression positively correlated with the malignancy and poor prognosis of glioma patients. DANCR contains an miR-33a-5p binding site, and miR-33a-5p was also decreased in glioma tissues and cells compared to normal brain tissues and cells. Further, the down-regulation of miR- 33a-5p positively correlated with the malignancy and poor prognosis of glioma patients, and DANCR expression in glioma tissue negatively correlated with miR-33a-5p expression. While down-regulation of DANCR increased miR-33a-5p expression, the miR-33a-5p mimic reduced DANCR-WT luciferase but not DANCR SMUT. DANCR pull-down showed the expression of miR-33a-5p, but the miR-33a-5p mimic enhanced the knockdown of DANCR-induced inhibition of cell proliferation, migration and EMT, and increased apoptosis. However, anti-miR-33a-5p reversed the effects of si- DANCR on cell malignancy and DANCR knockdown remarkably reduced the increase of tumor volumes in xenograft mouse models. The knockdown of DANCR increased tumor tissue expression of miR-33a-5p, reduced EMT and increased apoptosis. Our study therefore provides novel insights into the functions of the LncRNA DANCR-miR-33a-5p axis in glioma tumorigenesis.