A. Western Blot analysis of USP22, CD133 and H2Bub1 in the parental tumorsphere cells and tumorsphere cells that survived a 72h of 1, 2, 4 and 6 μM cisplatin treatment, indicating survived tumorsphere cells have elevated USP22 protein with the increase of cisplatin concentration. B. Cytotoxic effects of cisplatin in GFP-CTRL and USP22-KD cells. C. Flow cytometry analysis of apoptosis (upper panel) and quantitative analysis of induced apoptosis (lower panel) in GFP-CTRL and USP22-KD cells cisplatin treatment (**P < 0.01, compared with control), demonstrating USP22 knockdown significantly sensitized CICs to cisplatin.