PDCD1 and central nervous system cancer: We found that cluster 2 had a remarkably high expression level of most of the immune checkpoints including PD-1 (PDCD1), PD-L1 (CD274), and CTLA-4 (CD276), and most of these trends were consistent between IDH-mutant and IDH-wildtype gliomas (Figures 5A–C and Supplementary Figures S2A–C).