CCL7 and glioblastoma: Glioblastoma CSC-derived exosomes can stimulate M2 polarization, programmed death-ligand 1 (PD-L1) expression, and the production of monocyte chemotactic protein 3 (MCP-3) and CXCL1, which promote myeloid cell recruitment, through the STAT3 pathway in glioblastoma [92].