CXCR4 and central nervous system cancer: Since it is well known that CXCL12 activates members of the MAP kinase family in gliomas via its G-protein-coupled receptors CXCR4 and CXCR7 [22, 27, 28], it seems obvious that CXCL12 regulated CCL2 and SAA2 expression during cellular dormancy entry via these pathways.