CXCL12 and central nervous system cancer: Other authors showed how chemokine receptor pairs CXCL12/CXCR4/CXCR7, CXCL16/CXCR6, and CX3CL1/CX3CR1 are involved in tumor progression and that GBM-associated macrophages and microglia are also characterized by expression of these chemokine receptor pairs indicating a pivotal role of this expression profile in GAM biology in gliomas [44,82].