Granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), and IL-1 are all tumor-derived cytokines that have been shown to facilitate MDSC infiltration into the TME [31]. This evidence concerns the gene CCL2 and neoplasm.