PDCD1 and glioblastoma: In addition to chemotherapy, immunotherapies, such as CAR-T [68,69,70,71] and immune checkpoint inhibitors of cytotoxic T lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein 1 (PD-1), and programmed cell death protein 1 ligand (PD-L1) [72,73,74], have been recently investigated for GBM treatment.