CCL2 and central nervous system cancer: In addition, the expression of Ccl2 gene encoding the chemokine that binds with CCR2 and Csf1 gene encoding the cytokine that induces the differentiation of monocytes into Mφs are highly upregulated in human high-grade gliomas [26, 27] and functionally contribute to glioma progression [24, 28, 29], totally supporting the idea that GSCs self-construct their own niche dominantly involving TAMs through remotely communicating with host CCR2+ BM-derived inflammatory monocytes, but rarely through expanding the resident microglias in brain.