Particularly, the immunosuppressive ground created by GAMs, which inhibits the cytotoxic activity of T-cells and explains why GBM patients do not respond to immune therapy [90], is mainly due to the expression of PD ligands PD-L1/2, and the cytotoxic T lymphocyte-associated protein 4 (CTLA-4) ligands CD80 and CD86 [91]. Here, CTLA4 is linked to glioblastoma.