ARG1 and neoplasm: Monocytes that are attracted to the tumor generally differentiate into macrophages, typically M2 macrophages that are characterized by arginase 1 (Arg1) expression and IL-10 known as immunosuppressive markers that contribute to immune evasion of cancer, whereas M1 macrophages contributing to anti-tumor activity express nitric oxide synthase (NOS2) and secret tumor necrosis factor-alpha (TNFα).