Through geospatial analyses of human GBM tumors, MDSCs were found in close proximity to CD133+ and SOX2+ GSCs; these GSCs were found to secrete the cytokine macrophage migration inhibitory factor (MIF) to recruit MDSCs (218), as well as chemokine secretion of CCL2 and CCL5 (15). Here, CCL2 is linked to glioblastoma.