USP22 and central nervous system cancer: Considering previous observations that USPs are involved in the stem cell properties of glioma, such as the association of USP22 with the stemness and tumorigenicity of glioma [28], and EPG5 deubiquitination through USP8 to maintain stemness [29], we hypothesized that the USP8 inhibitor DUB-IN-1 can possibly inhibit the stemness of glioma.