MMP9 and glioblastoma: EVs with exosome characteristics isolated from GBM patients’ plasma have been found abundant in proteins that regulate hypoxia, such as pentraxin 3 (PTX3), matrix metalloproteinase 9 (MMP9), platelet-derived growth factor (PDGF)AB/AA, interleukin-8 (IL-8), CD26, plasminogen activator inhibitor 1 (PAI1), and caveolin 1 (CAV1).