PDCD1 and glioblastoma: In glioblastoma (GBM) cells, PD-1 ligands are mainly expressed as also reported in biopsies, hence the PD-1L impediment binding to its receptor PD-1 has been demonstrated to induce an immune escape mechanism validating that PD-1/PD-L1 inhibited could be a target for cancer immunotherapy of different tumor types [5].