Furthermore, GBM express immune checkpoint ligands like programmed cell death ligand 1 (PD-L1) and induce the expression of inhibitory molecules on the surface of CAR T cells, such as programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) [36]. Here, CTLA4 is linked to glioblastoma.