CCL2 and glioma: Depending on the level of COX-2 (Fujita et al., 2011; Kosaka et al., 2014), PGE2 promoted the secretion of IL-8 from glioma cells through autocrine (Venza et al., 2011, 2012), advanced the migratory response of M-MDSCs to MCP-1, and promoted the expression of ARG1 in PMN-MDSCs.