USP22 and cancer: Ubiquitin-specific protease 22 (USP22) is a deubiquitinating enzyme and an integral component of the 11-gene polycomb/cancer stem cell signature; it is an important subunit of the human Spt-Ada-Gcn5 acetyltransferase (hSAGA) complex that is required for transcriptional regulation and cell cycle progression [4, 5].