CCL2 and neoplasm: They are recruited to the tumor sites in response to cytokines (such as colony stimulating factor (CSF)-1, interleukin (IL)-34, and members of the vascular endothelial growth factor (VEGF) family) and chemokines (such as chemokine C-C motif ligand 2 (CCL2) and CCL5) and differentiate into TAMs [11].