Radiation sensitivities of the cultured cell lines established from 31 human esophageal squamous cell carcinoma (ESCC) and 20 other human cancer tissues were investigated with the colony-formation assay. There was a large variation in radiosensitivity among the 51 cell lines. MRE11 and BRCA1 genes were involved in the homologous recombination (HR) pathway. Radiosensitivities of BRCA1- or MRE11-defective cell lines were higher than those of other cell lines. Twenty-six of 28 ESCC lines tested had mutations in the p53 gene. Variance in radiosensitivity was not explained according to the status of p53. Unusual radiosensitivity was observed in one ESCC cell line. Western-blot analysis and immunohistochemical staining demonstrated that DNA-PKcs had low levels and was not phosphorylated after X-irradiations. DNA-PKcs is involved in the non-homologous end-joining (NHEJ) pathway. Our data suggest that genes which play a key role in the HR or NHEJ pathway on DSBs are mutated in cells having unusual radiosensitivity.日本放射線影響学会 第４６回大
