However, Rad51 protein was decreased in the gefitinib or cotreatment group, and Rad51 plasmid overexpression could reverse the combinational effects, which suggested that gefitinib decreased Rad51 levels to inhibit the HR repair pathway and block of the HR repair pathway was a key reason for the accumulation of DNA damages in HCC cells. The gene discussed is RAD51; the disease is hepatocellular carcinoma.