DNA-DAMAGE INDUCTION AND TUMOR-CELL RADIOSENSITIVITY - PFGE AND HALO MEASUREMENTS

Purpose: To test whether induction of DNA damage is correlated with tu mour-cell radiosensitivity. Materials and methods: Initial DNA damage caused by X-irradiation was measured in ten human tumour cell lines, w hich largely differed in radiosensitivity, using either the pulsed-fie ld gel electrophoresis assay or the halo technique. Results: None of t he parameters of DNA damage correlated with any parameter of cellular radiosensitivity. This was not only true when the analysis was perform ed on all data but also when the analysis was performed after separati ng the cell lines into radioresistant and sensitive groups. Even when differences in chromosome number, ploidy and cell cycle distribution w ere taken into account, no significant correlations were obtained. Con clusions: Contrary to previous suggestions, differences in the number of double-strand breaks induced or chromatin-related 'presentation' of DNA lesions, measured by pulsed-field gel electrophoresis or halo res pectively, are generally not the dominant factors determining tumour-c ell radiosensitivity.