For example, dysregulations or polymorphisms of PER1, PER2, PER3, CLOCK, BMAL1, CRY1, CRY2, and NPAS2 were common in ovarian cancer, prostate cancer, leukemia, gliomas, hepatocellular carcinoma, and colorectal cancer [14,15,16,17,18,19,20,21,22,23,24]. Here, PER2 is linked to central nervous system cancer.