CDC25A is known as an oncogene to assist both G1/S and G2/M progression in various types of cancers including HCC.26, 27, 28 Our present study showed that NPAS2 facilitated G1-S transition via transcriptional upregulation of the CDC25A and subsequent dephosphorylates CDK4(Tyr), CDK6(Tyr24) and CDK2(Thr14/Tyr15) in HCC, strongly suggesting that CDC25A is a vital bridge between circadian rhythm and cell cycle regulation. The gene discussed is CDK6; the disease is hepatocellular carcinoma.