However, CHK2 inhibition only further improved the percentages at S phase of HepG2shMus81 and Bel‐7402shMus81 cells under EPI treatment to 92.30% and 74.96% with a decrease in percentages at G2/M phase to 1.97% and 22.93%, suggesting that CHK2 inhibition could aggravate S‐phase arrest, but not rescue it and CHK2, therefore, may not be the primary regulator in S‐phase arrest of Mus81‐suppressed HCC cell under EPI treatment. This evidence concerns the gene MUS81 and hepatocellular carcinoma.