Studies have found that both subtypes of MDSCs along with monocytes and neutrophils are recruited by chemokines, including C-C Motif Chemokine Ligand 2 (CCL2), CCL7, and chemokine (C-X-C motif) ligand 1 (CXCL1), produced by tumor cells and TAMs in neuroblastoma and other tumors (64–67). Here, CCL2 is linked to neoplasm.