Conversely, in USP21-KO HCT-15 cells, the size of tumor spheroids was noticeably smaller when treated with vehicle compared to vehicle-treated Ctrl HCT-15 cells (Fig. 4D, E: USP21-KO HCT-15 treated with vehicle vs. Ctrl HCT-15 treated with vehicle). This evidence concerns the gene USP21 and neoplasm.