In contrast, in response to secretion of cytokines by tumor cells, M2 macrophages may release hepatocyte growth factor, TGF-β, VEGF-A, FGF-2, platelet-derived growth factors, placental growth factor, insulin-like growth factor-1, IL-1, IL-10, IL-8, CCL17, CCL22, SDF-1 (CXCL12), PD-L1, PD-L2, arginase, and prostaglandin E2 (22, 48, 59, 66–68). Here, CXCL12 is linked to neoplasm.