IDO1 and acute myeloid leukemia: AML shares similar immune evasion mechanisms with solid tumors, including the upregulation of amino acid metabolic enzymes such as indoleamine 2,3-dioxygenase-1 (IDO1) [4] and arginase-2 (ARG2) [5], downregulation of antigen presentation molecules, overexpression of inhibitory T cell ligands, and the production of reactive oxygen species.