Arginine in TME is rapidly catabolized by immunocyte expressing arginase 1 (ARG1), like myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), M2-macrophages, creating a state of arginine deficiency and limiting the availability of T cells to arginine, which suppresses antitumor immunity [186]. This evidence concerns the gene ARG1 and hyperinsulinemic hypoglycemia, familial, 4.