Hyperthermic radiosensitization of chicken Blymphocyte DT40 and Its derivatives laking NHEJ and/or HR pathways of DNA DSBrepair

抄録

To explore the roles of two major pathways of DNA double-strand break repair, i.e., NHEJ and HR, in hyperthermic radiosensitization, we examined chicken B lymphocyte DT40 cells and its derivatives lacking Ku70, DNA-PKcs or Rad54. When these cells were irradiated with X-ray after 20 or 40min-treatment at 46°C, the radiosensitivity was enhanced in any of mutants as well as wild-type cells. Notably, however, in Ku70-/- and DNA-PKcs-/-/-, which are consisted of two subpopulations with greatly different radiosensitivity, the radioresistant fraction, rather than the radiosensitive fraction, was sensitized. It has been considered that the radioresistant fraction of these cell lines might represent cells in late S- and G2-phases, with efficient repair through HR. In conjunction with this, the present observation suggested that hypethermia might have inhibited homologous recombinational repair of DNA double-strand breaks. [J Radiat Res 44:428 (2003)]