CXCL16 and central nervous system cancer: Here, the terminus ‘inverse signaling’ describes the fact that the soluble chemokine ligands chemokine (C-X-C motif) ligand 16 (CXCL16) and chemokine (C-X3-C motif) ligand 1 (CX3CL1) were able to induce anti-apoptotic effects after binding to their transmembrane counterparts in ligand-bearing glioma cells [38,39].