Monocyte chemotactic protein 1 (MCP-1, CCL2) secreted by glioma cells mediated the recruitment of CCR2+ monocytes and macrophages (Chen Z. et al., 2017; Vakilian et al., 2017), and CX3CL1 induced the infiltration of CX3CR+ microglia (Hambardzumyan et al., 2016). Here, CCL2 is linked to glioma.