Abstract: Objective To study the repeatability and stability of repeated irradiation method to establish the radioresistant esophageal cancer cell line and to observe the variation of radiosensitivity between the radioresistant cell line and its parental cell line.Methods A radioresistant cell line,TE13R120,was established from a human esophageal squamous cancer cell line TE13 by repeated irradiation,120 Gy in total dose.Colony formation assay was used to calculate the radiation biology parameters and detect radiation resistance.Besides,multi-target single-hit model was adopted to fit dose-survival curve of TE13 and TE13R120 cell.The cells were cultrured for 8 d,the cell growth curve was drawn to calculate the population doubling time of TE13 and TE13R120 cell.Results After radiation by 120 Gy in total dose,TE13R120 cell line showed significant radioresistance compared with its parental cells TE13.The D0 ,Dq,and N of TE13R120 showed siguificant radioresitance as compared with those of TE13(2.36,2.17,2.50 vs 1.90,1.11,1.80),but SF2 ,a/β were lover in the former cell line(0.53,2.67 vs 0.73,8.00).The population doubling time of TE13R120 was 20.70 h,longer than its parental cell line TE13 (17.67 h).The results were similar with those of the first establish line.Conclusion The radioresistant cell line established by repeated radiation exposures and gradually screening is reliable since it can build a stable cell line with radioresistant phenotype.

Key words: esophageal neoplasms, radiatoon tolerance, colony forming units assay