Under the influence of tumor-derived cytokine and growth factors [e.g., VEGF, granulocyte macrophage colony stimulating factor (GM-CSF), macrophage colony-stimulating factor (M-CSF), TGF-β, IL-4, IL-6, and IL-10], MDSCs acquire inhibitory activity against various anti-tumor immune cells. This evidence concerns the gene CSF1 and neoplasm.