Microglia and macrophages are recruited as activated cells by GBM through the release of chemoattractant factors, mainly monocyte chemoattractant protein 1 (MCP1), colony-stimulating factor-1 (CSF-1), granulocyte-macrophage colony-stimulating factor (GM-CSF), and osteopontin [70,71]. Here, CCL2 is linked to glioblastoma.