MMP9 and glioblastoma: TAMs, being the largest stromal population in GBM, are generally described as integral microenvironmental components contributing to mesenchymal transition by expressing pro- (M1) (e.g., TNFα) and anti-inflammatory (M2) (e.g., TGFβ), pro-angiogenic (e.g., VEGF), and extracellular matrix remodeling factors (e.g., MMP9) (Fig. 1a) [11, 35, 119].