PDCD1 and glioblastoma: In a long-term (>10 days) cytotoxicity assay against HER2+/PD-L1+ U373-GBM, PD-1 modulation with a nonsignaling PD-1TR resulted in a markedly improved sustenance of CAR28ζ-mediated tumor lysis (P < 0.0001, two-way ANOVA with the Tukey test; Fig. 2C).