In the TME, MDSCs are accumulated to suppress immune function and promote tumor growth through inducing some tumor-derived factors, cytokines and/or chemokines such as interleukin (IL)-6, interferon (IFN)-γ, IL-1β, granulocyte-macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor (TNF)-α and vascular endothelial growth factor (43, 44). Here, CSF2 is linked to neoplasm.