ARG1 and neoplasm: High levels of growth factors and cytokines, such as TGF-β, IL10, and Arg1, as well as chemokines, CXCL2, CXCL8, and CXCL12 [177], attract other immunosuppressive cells, in particular Tregs [172], thereby promoting tolerance and tumor evasion by suppressing proinflammatory CD4+ type 1 (Th1) helper T cells and CD8+ cytotoxic T cells [178].