M1 macrophages, characterized by the expression of the inducible type of nitric oxide synthase (iNOS), have pro-inflammatory and anti-tumor functions, whereas M2 macrophages express high levels of anti-inflammatory cytokines (e.g., IL-10) and have potent arginase-1 (Arg1) activity to promote tumor cell growth [76]. Here, ARG1 is linked to neoplasm.