Many studies have reported that high levels of TGF-β, EGF, MMP-2, MMP-9 and IL-10, and low levels of IL-12 can be produced by M2 polarized glioma-associated microglia/macrophages to promotes invasion, proliferation, immune evasion and angiogenesis of glioma [43]. Here, MMP9 is linked to central nervous system cancer.