CCL2 and cancer: All three of these factors have been implicated in aspects of MDSC development and trafficking/recruitment, with G-CSF considered one of the main growth factors promoting myelopoiesis and MDSC expansion (23), and both CXCL2/MIP-2 and CCL2/MCP-1 reportedly implicated in MDSC mobilization, recruitment, and function in various types of cancer (24).