FASN and neoplasm: Despite normal TCR-induced proliferation, FASN deletion impaired the TCR-dependent upregulation of Treg activation and maturation markers, including GITR and CD44; moreover, de novo fatty acid synthesis mediated by FASN contributes to the functional maturation of Treg cells, and the loss of FASN from Treg cells inhibits tumor growth, which may be related to dysregulated activation of PI3K in intratumoral Treg cells [5].