The results of IHC demonstrated that the expression level of KYNU was higher in high-grade glioma compared to low-grade glioma (Supplementary Figure S3A), and the expression level of ALDH2 was higher in low-grade glioma (Supplementary Figure S3B), confirming the results from sequencing that KYNU was hazardous factor and ALDH2 was protective factor. This evidence concerns the gene ALDH2 and central nervous system cancer.