CXCL12, which is highly produced in the tumor environment, has been shown to not only mediate recruitment and migration of monocytes to the tumor tissue, but also participate in differentiating macrophages towards immunosuppressive M2 macrophages by up-regulating chemokine [C–C motif] ligand 1 (CCL1) expression [60]. Here, CCL1 is linked to neoplasm.