FLI1 and Ewing sarcoma: Genetic and pharmacologic inactivation of USP7 was shown to reduce Ewing sarcoma growth, although the substrate(s) through which USP7 acted on Ewing sarcoma growth remained unclear.[18] Genetic depletion of USP19 reduced Ewing sarcoma cell growth in vitro and in mice largely through destabilizing EWS–FLI1 proteins.[19]