USP21 and malignant colon neoplasm: Additionally, cell proliferation was markedly decreased in these USP21-KO colon cancer cells compared to the control cells (Fig. S3A: USP21-KO HCT-15 vs. Ctrl HCT-15; Fig. S3B: USP21-KO HT-29 vs. Ctrl HT-29; Fig. S3C: USP21-KO SW480 vs. Ctrl SW480).