PER1 and hepatocellular carcinoma: The risk score of each HCC sample was calculated with the following formula: Risk score = ( − 0.197070704 * expression of IL7R) + (0.032065529 * expression of BATF) + (0.06105135 * expression of PRDX1) + (0.02338793 * expression of HSPA8) + (0.114580331 * expression of AHSA1) + (0.062159747 * expression of RGS2) + (0.037404701 * expression of DYNLL1) + (0.282509962 * expression of CHORDC1) + (0.109884375 * expression of NUDC) + (0.054986533* expression of OAZ1) + ( − 0.073910694 * expression of PER1) + (0.211991659 * expression of ZC3HAV1) + (0.058564557 * expression of CDV3).