CXCR4 and central nervous system cancer: In the glioma microenvironment, SDF-1 is mainly derived from glioma cells and microglia and binds to CXCR4+ cells including microglia, macrophages, monocytes, endothelial cells and glioma cells themselves to initiate G-protein subunit dissociation, and the subsequent stimulation of mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K) and phospholipase C (PLC) (63, 76–80).