ABSTRACT
PURPOSE: The difference in radiosensitivity between two isogenic tumour cell lines was evaluated to determine whether factors such as sublethal and potentially damage repair, DNA double-strand break repair and fidelity of repair can be related to differences in radiosensitivity. MATERIALS AND METHODS: The cell lines used were the ovarian carcinoma A2780s and a radiation-resistant derivative A2780cp. Radiation response was measured in terms of cell survival, recovery of sublethal (SLD) and potentially lethal damage (PLD), induction of and recovery of DNA strand breaks, and fidelity of DNA repair using a cell-free plasmid assay. RESULTS: While A2780cp was more resistant to radiation than A2780s, it showed less ability for recovery of SLD and PLD. DNA strand-break induction was the same for both cell lines, while only at very high doses did A2780cp show greater DNA strand-break recovery than A2780s. Fidelity of rejoining DNA was significantly higher in the A2780cp cell line. CONCLUSION: The difference in radiosensitivity between these two cell lines was not related to recovery of PLD or SLD or to the induction of DNA damage. It appears that fidelity of DNA rejoining, which was significantly higher in the resistant cell line, may be related to the difference in radiosensitivity.
