USP4 and glioma: To begin, qRT-PCR revealed that USP4 expression was up-regulated in all four glioma cell lines when compared to normal control NHAs cell lines (Figure 11A), with the highest expression in U87-MG and LN229 cell lines, so gene knockdown was performed in these two cell lines (Figure 11B, *P<0.05, **P<0.01).