Estimation of DNA single-strand breaks by single cells gel electrophoresis in tumor cells

To estimate the frequency of single-strand breaks on a single cell level the so-called comet-assay (single cell gel electrophoresis) is a well-established technique. We present a modified protocol suitable for testing primary tumors, a kind of tissue very uneasy to be analysed in former single cell gel electrophoresis assays. Tumor cells of 12 studied cases showed a typical dose-rate effect on in vitro irradiation with different X-ray doses, as observed in peripheral blood leukocytes. Interestingly, the repair capability of primary tumor cells was lower than that of peripheral blood leukocytes of the same patients.