CCL2 and cancer: During cancer progression, microglia cells polarize in different phenotypes: the M1 phenotype induces reactive oxygen species (ROS) and nitric oxide (NO) and releases proinflammatory cytokines (IL-1 β, IL-6, TNF α, CCL2), resulting in anti-tumor effects [46,47,48]; the M2 phenotype regulates anti-inflammatory cytokine secretion (TGF-β and IL-10) as well as immunosuppressive factors (ARG-1 and CD36), leading to pro-tumor consequences [49,50,51].