CSF2 and neoplasm: Various tumor-derived factors have been described to induce MDSC, these include but are not limited to granulocyte macrophage-colony stimulating factor (GM-CSF), macrophage-colony stimulating factor (M-CSF), prostaglandin E2 (PGE2), vascular endothelial growth factor (VEGF), stem cell factor (SCF), interleukin-6 (IL-6), IL-10 and IL-1β [7, 8].