CAR T cell immunotherapy has achieved great success in CD19+ B-cell malignancies. Whether this new generation of cell-based immunotherapy can be applied to solid tumors remain to be investigated, partly due to hostile immune-suppressive tumor microenvironment which favors tumor growth but not immune system. Signaling pathway of programmed death 1 (PD-1) and its ligand PD-L1 plays an important role in suppressing immune response against tumors. PD-L1 is over-expressed in 88% of glioblastoma.