TGFB1 and cancer: Additionally, macrophages facilitate cancer progression in various cancers by suppressing T cell effector function through multiple processes, including expression of inhibitory checkpoint ligands such as programmed cell death-ligand 1 (PD-L1), secretion of inhibitory cytokines such as TGF-b and IL-10, and depletion of amino acids, including arginine and tryptophan 28–31.