CDK4 and cancer: To confirm the key genes involved in increased expression and druggability, the GEPIA server (http://gepia.cancer-pku.cn) was utilized to examine the expression levels of the NOTCH1, TOP2A, CD44, PTPRC, CDK4, HNRNPU, and PDGFRA genes in 163 GBM tumor samples and 207 healthy samples obtained from the TCGA (The Cancer Genome Atlas) database.