CLOCK and central nervous system cancer: To investigate the role of CCGs in all grades of glioma, including grade 2-4, we firstly analyzed the differential expression of CCGs in glioma grade and found that 11/13 CCGs, except for CLOCK and PER1, were recognized as DEGs in TCGA (Figures 3(a) and 3(b)) and CGGA (Figures 3(c) and 3(d)), respectively.