CHEK1 and hepatocellular carcinoma: When HepG2shMus81 and Bel‐7402shMus81 cells was treated with CHK1 inhibitor and then EPI, the percentages of these two cells at S‐phase were significantly decreased to 28.14 and 21.84% with a obvious increase in percentages at G2/M phase to 65.60 and 69.10%, which were close to the levels of EPI‐treated HepG2shCtrl or Bel‐7402shCtrl cells (Fig. 4), suggesting an apparent involvement of CHK1 in S‐phase arrest of Mus81‐depleted HCC cells under EPI treatment.