PER3 and central nervous system cancer: Besides, the expression of eight CCGs (CRY2, DBP, NR1D1, NR1D2, PER2, PER3, RORA, and TIMELESS) was negatively regulated by methylation and positively regulated by CNV in glioma, which is consisting with previous studies that DNA methylation and CNV can promote abnormal gene expression [39–41].