Compared with the paired peritumoral tissues, the mRNA levels of the Per1, Per2, Per3 and Cry2 genes in HCC tissue were significantly lower (P<0.05), while no significant difference was observed in the expression levels of CLOCK, BMAL1, Cry1 and casein kinase 1ɛ (CK1ɛ; P>0.05). This evidence concerns the gene PER3 and hepatocellular carcinoma.