Fragility of telomeres after bleomycin and cisplatin combined treatment measured in human leukocytes with the Comet-FISH technique.

UNLABELLED THE AIM of the present study was the comparative investigation of action of widely applied anticancer preparations: cisplatin (cis-DDP) and bleomycin (BLM) on total DNA and telomeres damage in human blood cells. METHODS The "Comet-FISH technique" -- single cell gel electrophoresis ("comet assay") in combination with fluorescent in situ hybridization (FISH) was used for this purpose. This newly applied combined approach permits to detect on the same specimen the total DNA damage in individual cells and evaluate specific DNA sequences as well. Telomere -- specific -- PNA (peptide nucleic acid) probes were used for the localization of telomeres in the comet's head and their migration to the tail. THE RESULTS obtained indicate that in control variants, due to DNA metabolism and handling, approximately 7% of the DNA and 17% of the telomeres were found in the tail. In cells treated with BLM alone, telomeres leak out with equal probability as total DNA. In turn, the combination of cis-DDP with BLM reduces telomere migration more than the migration of total DNA due to cis-DDP crosslinking effect. Thus, preferentially telomeric action of the cis-DDP can be concluded. CONCLUSION The Comet-FISH approach permitted us to reveal the induction of DNA breaks with BLM and its modification due to platinum-crosslink formation, using telomeric PNA probes.