Validation of promoter methylation using the UALCAN database revealed that the promoter methylation level of ASPM, AURKA, BUB1, KIF2C, NCAPG, NCAPH, and NUF2 was lower than normal samples in GBM that indicates higher expression of these hub genes as against that of BUB1B, CCNA2, CCNB2, MELK, PBK and TOP2A having higher promoter methylation level than normal samples (see Supplementary Figure S4a). This evidence concerns the gene CCNA2 and glioblastoma.