USP21 and cancer: NANOG stability, and by extension possibly that of NANEPs, is regulated as suggested by various findings, including i- aspirin treatment decreases the levels of stable NANOG protein in cycloheximide-treated cancer cells33, ii- PIN1 enhances the stability of phosphorylated NANOG74, iii- SRSF3 promotes NANOG mRNA nuclear export and thus protein production75, iv- the deubiquitinase USP21 stabilizes NANOG76.