FLI1 and Ewing sarcoma: Ubiquitin carboxyl‐terminal hydrolase 7 (USP7) was identified from a CRISPR screen as a dependency for p53‐wild‐type (WT) Ewing sarcoma[18] and the deubiquitinase Ubiquitin carboxyl‐terminal hydrolase 19 (USP19) was found to stabilize both EWS–FLI1 and EWSR1 proteins.[19] However, the multiple roles of USP7 on targeting both tumor suppressors and oncogenes,[20] as well as the pleiotropy of USP19[21, 22, 23, 24] complicate their applications to treat Ewing sarcoma.