Reduced PD-L1 expression in IDH-mutated glioma implies a stronger T cell activation, as PD-L1 is a cellular surface protein that downregulates the immune system and promotes self-tolerance through suppressing T cell activity.96 In addition, D-2-HG-derived DNA methylation results in epigenetic silencing of both PD-1 and PD-L1 in glioma.97,98 However, the reduced expression of PD-1/PD-L1 in IDH-mutated glioma may not result in stronger antitumour T cell immunity. This evidence concerns the gene CD274 and central nervous system cancer.