COMET ASSAY STUDIES OF RADIATION-INDUCED DNA-DAMAGE AND REPAIR IN VARIOUS TUMOR-CELL LINES

We used the 'comet assay' to compare the amount of radiation-induced D NA damage in three tumour cell lines (MeWo, PECA 4451 and PECA 4197) a nd the extent of DNA repair in two of these lines (MeWo and PECA 4197) . Tumour cells were irradiated with X-rays (0.1-10 Gy), embedded in ag arose on slides, lysed with sodium dodecyl sulphate and exposed to an electric field. DNA migrated within the agarose and formed comets whos e length depended on the amount of DNA damage. When the cells were inc ubated at 37 degrees C for various time intervals before electrophores is started, the comets shrank in the course of time, indicating repair of DNA damage. All three cell lines showed the same extent of DNA dam age after radiation exposure, despite the fact that in the colony-form ing assay MeWo and PECA 4451 were much more sensitive to radiation exp osure than PECA 4197. The repair characteristics, however, were marked ly different for MeWo and PECA 4197 cells. PECA 4197 cells showed a mu ch faster restoration of the original shape of the cell nucleus than M eWo cells.