CD274 and neoplasm: In truth, the relatively low mutation burden (5), low levels of PD-L1 expression (6), immunosuppressive tumor microenvironment (TME) with abundant myeloid-derived suppressor cells (MDSC; ref. 7), T-cell dysfunction with exhaustion (8), and sequestration of T cells in the bone marrow (9), render GBM refractory to ICI.