USP7 and cancer: USP7 deubiquitinates and hence stabilizes a vast array ofproteins.Some of its important substrates are the tumor suppressors p53 andPTEN; and the MDM2/MDMX oncoproteinswhich are considered negative regulators of the tumor suppressor p53. Additionally, USP7 stabilizes the histone methylaseEZH2, a critical protein that is involved in malignant tumor progressionand invasion. Recent evidence furthershowed that USP7 significantly promotes the stabilization of the BCR/ABLfusion protein in chronic myelogenous leukemia (CML) and that itsoverexpression promotes the survival of CML cells.