CD274 and glioblastoma: Even though the data on the expression of PD-1/PD-L1 in GBM patients are largely correlative based on immunohistochemical antibody staining or TCGA data mining (67, 70, 71), they nevertheless represent the first steps forward in a new area of research in the GBM field, which is to understand the biological function of PD-1/PD-L1, T-cell infiltration and function, and their interaction with TAMs.