Knockdown of USP15 inhibits cell proliferation of glioma cells in Cell Counting Kit-8 assays in vitro. (A) Analysis of USP15 expression in a HEB cell line and typical glioma cell lines. Western blot analysis revealed that USP15 protein level was upregulated in U87-MG and U251-MG cells compared with expression in the HEB cell line. (B) USP15 was knocked down successfully in U87-MG cells, as revealed by western blot analysis. (C) Densitometry analysis demonstrated the efficiency of USP15 depletion in U87-MG cells (*P<0.001). (D) USP15 was knocked down successfully in U251-MG cells, as determined by western blot analysis. (E) Densitometry analysis demonstrated the efficiency of USP15 depletion in U251-MG cells (*P<0.001). USP15, ubiquitin specific peptidase 15; HEB, human normal glial; NC, negative control.