These IHC staining revealed that the protein expression level of POLR1D was higher in high-grade glioma than low-grade glioma (Supplementary Figure S3A), and the protein expression level of PDE2A was lower in high-grade glioma (Supplementary Figure S3B), in accordance with the results from bioinformatic analyses that POLR1D was a hazardous and PDE2A was a protective factor. This evidence concerns the gene POLR1D and central nervous system cancer.