Fig. 3

circMMP9 acts as a sponge of miR-124. a Profile of the top 20 upregulated and downregulated miRNAs in human adjacent normal tissues and GBM tissues. Green indicates low expression, and red indicates high expression. The arrow represents miR-124-3p (miR-124). b Detailed information for the top 20 upregulated and downregulated miRNAs according to the extent. c The binding sites of miRNAs and circMMP9 were predicted by RegRNA (http://regrna.mbc.nctu.edu.tw/). d-e miR-124 expression was detected by qRT-PCR in treated U87 or U251 cells (***P < 0.001). f Binding of circMMP9 and miR-124 was analyzed using the pull-down assay (***P < 0.001). g Colocalization of circMMP9 and miR-124 was measured using FISH in transfected U87 and U251 cells. h The putative binding sites of miR-124 on the circMMP9 wild-type (WT) or mutated sequence are shown. i A luciferase reporter assay was performed to detect the activity of circMMP9 in U87 cells cotransfected with miR-124 or scramble and circMMP9 or vector (***P < 0.001). (J) U87 cells were cotransfected with miR-124 or scramble and mutated circMMP9, and the activity of circMMP9 was detected using the dual-luciferase reporter assay after transfection. k miR-124 expression was detected by qRT-PCR in GBM tissues and normal brain tissues (n = 18, P < 0.05). l miR-124 expression was measured via IHC in GBM tissues and normal brain tissues (n = 18, P < 0.05). m Correlation between the expression of miR-124 and circMMP9 was evaluated by Pearson’s correlation test (r² = − 0.5152, P = 0.0287)