KITLG and neoplasm: It is known that in the tumor microenvironment, many known circulating factors including IL-6, IFN-γ, TGF-β, VEGF, G-CSF, GM-CSF, M-CSF, and SCF induce the recruitment, accumulation, and activation of MDSCs (28) and modulate MDSCs to produce more of NO and ROS (22).