Tumour-infiltrating MDSCs mediate potent pro-tumoural action and the immune suppression of T and NK cells through the expression and release of several molecules, such as programmed death-ligand 1(PD-L1), indoleamine 2, 3-dioxygenase (IDO), arginase 1 (ARG1), nitric oxide (NO), reactive oxygen species (ROS), IL-10 and TGF-β [49]. This evidence concerns the gene ARG1 and neoplasm.