SPP1 and glioblastoma: In addition to the CCL2/CCR2 axis, other studies have demonstrated additional targetable chemokine-receptor pairs, such as osteopontin (OPN)/αvβ5 integrin (69), lysyl oxidase (LOX)/ β1 integrin (40), and slit guidance ligand 2 (SLIT2)/ROBO1/2 (70), in GBM.