CCL2 and melanoma: Other cytokines, chemokines, and growth factors, such as chemokine (C-C Motif) ligand-2 (CCL2), GM-CSF, and vascular endothelial growth factor (VEGF), have been implicated in the expansion and recruitment of MDSCs to the tumor-microenvironment (3, 4), but were not observed to be increased in the circulation of advanced melanoma patients compared to healthy controls in this study.