ARG1 and neoplasm: This metabolic shift of “promoting storage and inhibiting consumption” collectively drives the transformation of macrophages towards an M2 phenotype, causing them to secrete more immunosuppressive cytokines (such as IL-10, TGF-β, CCL2, PD-L1) and pro-tumor growth factors (such as Arg-1), thus creating an immunosuppressive tumor microenvironment.