The infiltration of peripheral monocytes/brain-intrinsic microglia to the glioma sites is mediated by the interaction between C-C chemokine receptor type 2 (CCR2) expressed on monocytes and C-C motif chemokine ligand 2 (CCL2/MCP-1) expressed by glioma cells [41]. The gene discussed is CCL2; the disease is central nervous system cancer.