PTEN and acute lymphoblastic leukemia: For example, PTEN has been shown to be involved in the pathogenesis of T-ALL.47 In an earlier study, USP7 removed PTEN monoubiquitination, enhanced its nuclear export, and abolished its nuclear function.21 MDM2 is also a substrate of USP7, and inhibition of USP7 resulted in degradation of MDM2.