As one type of the most potent immunosuppressive cells, MDSCs facilitate tumor progression by suppressing T cell response, blocking natural killer cell activation, limiting dendritic cell maturation, and inducing regulatory T (Treg) cell generation (5), which are associated with high expression and secretion of immunosuppressive molecules such as interleukin (IL)-10, arginase-1(Arg-1), inducible nitric oxide synthase (iNOS) and ROS (5–7). This evidence concerns the gene NOS2 and neoplasm.