TP53 and neoplasm: Conversely, whereas USP4 and USP15 target p53-inhibiting ligases ARF-BP1 [14] and MDM2 [15], respectively, USP11 stabilizes p53 [16] as well as several other tumor suppressors including PML [17], BRCA2 [18] and Mre11 complex members MRE11 & RAD50 [2].