CCL2 and central nervous system cancer: CCL2, referred to as MCP-1 (Monocyte chemotactic protein-1), is secreted by glioma cells and binds to CCR2 expressed on microglia, inducing microglia to recruit to the glioma region and release interleukin-6 (IL-6) thereby promoting the invasion and growth of glioma cells (99, 100).