CSF3 and breast cancer: In BC, factors that contribute to the amplification and activation of MDSCs involve granulocyte-macrophage colony-stimulating factor (GM-CSF) (10, 11), granulocyte colony-stimulating factor (G-CSF) (11, 12), PGE2 (13, 14), vascular endothelial growth factor (VEGF) and interleukins (IL-1 (15), IL-6 (16), IL-13 (17), IL-17 (18), IL-20 (19), IL-33 (20), IL-34 (21)), macrophage migration inhibitory factor (MIF) (22), microRNAs (miRNAs) derived from tumor exosomes (23).