MMP9 and neoplasm: In the process of acquiring the M2 phenotype, GAMs secrete immunomodulatory and tumor-promoting factors such as TGF-β, epidermal growth factor (EGF), IL-10, and the proteolytic enzymes MMP-2 and MMP-9, thereby reinforcing an immunosuppressive tumor milieu within the glioblastoma microenvironment (31, 34).