Comparison of DNA repair protein expression and activities between human fibroblast cell lines with different radiosensitivities

In order to investigate the molecular basis of variation in response to ion ising radiation (IR) in radiotherapy patients, we have studied the expressi on of several genes involved in DNA patients with different normal-tissue r eactions to IR, and 3 from a control individual. For all 10 test cell lines , the cellular radiosensitivity was also known. Using Western blots we meas ured, in non-irradiated cells, the basal expression levels of ATM, Rad I an d Hus I, involved in the control of cellular DNA damage checkpoints, togeth er with DNA-PKcs, Ku70, Ku80; XRCC4, ligaseIV and Rad51, involved in radiat ion-induced DSB repair. We also analysed the in vitro enzymatic activities, under non-irradiated conditions, of the DNA-PK and XRCC4/ligaseIV complexe s. The levels of expression of the different proteins were similar in all t he cell lines, but the activities of the DNA-PK and XRCC4/ligaseIV complexe s showed some differences. These differences did not correlate with either the normal tissue response of the patient in vivo or with cellular radiatio n sensitivity in vitro. The activity differences of these enzyme complexes, therefore, do not account for the variation of responses seen between pati ents. (C) 2000 Wiley-Liss, Inc.