From the analysis above, we observed that several cell cycle related genes, such as CDKN2A/2B (14% vs. 3%), CDK4 (10% vs. 0) and RB1(10% vs. 0), were dominant in recurrent gliomas as compared to primary gliomas, so we further clustered the mutated genes according to their functional characteristics. Here, CDK4 is linked to central nervous system cancer.