Several neutralizing antibodies or inhibitors against tumor-derived factors or those receptors such as GM-CSF, GM-CSF receptor (GM-CSFR) [64], M-CSF, M-CSF receptor (M-CSFR) [88, 89], G-CSF [90], VEGF-A [91], or stem cell factor (SCF or KIT) [60] have been reported to inhibit MDSC expansion or mobilization. Here, CSF2 is linked to neoplasm.