For example, ubiquitin-specific protease 7 (USP7, also known as HAUSP) has been reported to stabilize several substrates including p53 [22], MDM2 [22, 23], N-Myc [24], HIF-1α [25] and PHF8 [26] to be critically involved in cancer initiation and progression. This evidence concerns the gene MDM2 and cancer.