However, CHK2 inhibition slightly increased the apoptosis of EPI‐treated HepG2shMus81 and Bel‐7402shMus81 cells to 87.96 and 64.81%, suggesting the regulating role of CHK1 but not CHK2 in EPI‐induced apoptosis of Mus81‐suppressed HCC cells. The gene discussed is MUS81; the disease is hepatocellular carcinoma.