IDH1 and central nervous system cancer: Some studies focusing on a limited number of genes have showed that IDH1-mutant glioma tends to display a lower expression of programmed death ligand 1 (PD-L1), a smaller number of tumor-infiltrating lymphocytes (TILs) [21], and a lower expression of genes related to CD8+ cytotoxic T lymphocytes (CTL) and IFN-γ [22] than those of the IDH1-wildtype counterparts.