Arginase-1 (ARG1), on the other hand, is often expressed by regulatory immune cells such myeloid-derived suppressor cells (MDSC) and exerts its suppressive function reducing the availability of L-arginine in the tumor microenvironment and thus causing the downregulation of the CD3ζ chain, and inhibiting T-cell proliferation (14, 15). This evidence concerns the gene ARG1 and neoplasm.