PER1 and hepatocellular carcinoma: However, compared to control-PB, HCC resulted in a significant upregulation of most clock genes in the hippocampus including Clock and Bmal1 (at ZT02 and ZT20, Figure 4A, B), Per1 (at ZT02 and ZT14, Figure 4C), Cry2 (at ZT20, Figure 4F) as well as Rev-Erba (at ZT20, Figure 4G) mRNA expression.