PER1 and hepatocellular carcinoma: Collectively, the results indicated an epigenetic alteration of several CCGs in HCC, including CLOCK, PER-1, RORA, RORB, CRY1, CRY2, NPAS2, NR1D1, and ARNTL2 in HCC, compared to adjacent, which may be potential biomarkers for patients with HCC.