S100A9 and neoplasm: IMCs are induced by tumor-derived inflammatory factors [e.g., VEGF, granulocyte-macrophage colony-stimulating factor (GM-CSF), prostaglandins, interleukin (IL)-1β, IL-6, IL-10, TGF-β, S100A8, and S100A9] (2, 6, 7) that stimulate tumor growth and myelopoiesis and block the differentiation of IMCs into mature effector cells such as DCs, macrophages, and granulocytes (8, 9).