Additionally, immunohistochemical staining of xenograft tumor tissues revealed reduced USP28 and MAST1 expression in the USP28-KO tumors compared with the mock control xenograft tumor tissues, while the expressions of USP28 and MAST1 were regained by reconstitution with USP28 or MAST1 (Fig. 6F). This evidence concerns the gene USP28 and neoplasm.