CSF2 and neoplasm: Immature MDSCs are generated from BM cells and then they expand and migrate to the TME where a complex milieu of tumor- or stromal-derived factors including vascular endothelial growth factor, IL-6, IL-1β, GM-CSF, transforming growth factor β as well as PGE2 modulate their suppressive function (Bunt et al., 2006; Ezernitchi et al., 2006; Bunt et al., 2007; Sinha et al., 2007).