These chemokines may initiate an inward migration of numerous leukocyte sub-populations (LPSs), including tumor-associated macrophages [52], myeloid-derived suppressor cells [53], tumor-associated neutrophils [54,55], T-regulatory [56], metastasis-associated macrophages, T helper IL-17-producing cells, and cancer-associated fibroblasts [57], which may bear CCR2 / CCR5 receptors, driving tumor aggression [36,58]. The gene discussed is CCR2; the disease is neoplasm.