MMP9 and glioblastoma: Because MMP-9 expression in macrophages was significantly upregulated by p-TNIIIA2 at 2.5 μg/ml (Figures 3A, C, D), which is 10 times lower than that was needed for eliciting GBM cell malignancy, macrophages might contribute to this feedback loop and elicit the aggressive malignancy of GBM cells through promotion of the continuous release and accumulation of the TNIIIA2 region by MMP-9-mediated cleavage of TN-C, result in subsequent PDGF production from GBM cells and make this feedback loop effectively work.