PER2 and central nervous system cancer: In line with this, downregulation or upregulation of the BMAL1/CLOCK target genes PER1, PER2, and CRY1 promote or suppress tumor onset and proliferation, respectively, in Lewis lung carcinoma (LLC), mammary carcinoma [80], pancreatic cancer [81], lung carcinoma [18], leukemia [82,83], glioma [84], ovarian cancer [85], and oral squamous cell carcinoma [86,87].