IL17A and neoplasm: Granulocyte colony-stimulating factor (G-CSF) [178,179], macrophage colony-stimulating factor (M-CSF) [178,179], GM-CSF [178,179], IL-6 [180], IL-1β [181], macrophage migration inhibitory factor (MIF) [182], polyunsaturated fatty acids, PGE2 [183,184], IL-17 [185], miRNAs derived from tumor exosomes (TEXs) [186,187], and vascular endothelial growth factor (VEGF) [188], which are produced by tumor cells or stromal cells in response to inflammation and chronic infection, are pivotal factors for the accumulation of MDSCs at tumor site.