USP21 and neoplasm: In addition, USP7 and USP21 enhance GATA3‐regulated activity in FOXP3‐expressing cells.[258] USP21 deficiency in Treg cells reduces FOXP3 expression, which reconciles the expression of Treg signature genes, and diminishes their suppressive activity.[259] Treg cells limit antitumor immune responses and facilitate tumor survival, therefore, anticancer immunotherapies recommend FOXP3 depletion in Treg cells by targeting USP7 and USP21.