Importantly, xenograft assays revealed a significant reduction in tumor growth and size in NSG mice implanted with USP21-KO HCT-15 cells compared to those implanted with Ctrl HCT-15 cells (Fig. 2K, L), strongly indicating the critical role of USP21 in the tumorigenicity of colon cancer cells. The gene discussed is USP21; the disease is malignant colon neoplasm.