In our study, higher level of γ-H2AX and reduced phosphorylation levels of DNA damage repair protein, including p-ATM and p-CHK2, in ERRFI1-overexpressed group than that in the control group suggest that prolonged process of DNA damage repair could contribute to ERRFI1-mediated radiosensitization in lung cancer cells. The gene discussed is CHEK2; the disease is lung carcinoma.