PDCD1 and central nervous system cancer: In this regard, Hu et al. (2019) showed that programmed death-1 (PD-1) gene knocked-out CD133-specific CAR T cells using CRISPR/Cas9 in addition to demonstrating more prominent proliferation and cytotoxicity against cancer cells could present profound resistance to inhibitory molecules in the glioma cell-bearing mice compared to the conventional CD133-CAR-T cells (Hu et al., 2019a).