In particular, GBM cells secrete many factors like hepatocyte growth factor (HGF), monocyte chemotactic proteins (MCPs), glial neurotrophic derived factors (GNDF), macrophage colony-stimulating factor (M-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and the transforming growth factor-β (TGF-β) [14,149]. Here, CSF2 is linked to glioblastoma.