Detection of incomplete chromosome elements and interstitial fragments induced by bleomycin in hamster cells using a...

The detection of incomplete chromosome elements (ICE, i.e., elements with telomeric signal at only one terminal end) and interstitial fragments induced by the radiomimetic compound bleomycin (BLM) was carried out in a Chinese hamster embryo (CHE) cell line using FISH with a telomeric peptide nucleic acid (PNA) probe. CHE cells were treated with 0, 1, 2.5, 5, and 7.5 microg/ml of BLM and chromosomal aberrations were analyzed in the first mitosis after treatment using a telomeric PNA probe. The relationship between chromosomal aberrations frequency and bleomycin concentration was of linear type (P < 0.05 for all type of aberrations analyzed, i.e., multicentric chromosomes, centric rings, interstitial fragments and ICE). After BLM treatment, about 20-30% of the analyzed metaphases contained one or more pairs of ICE. Acentric interstitial fragments, lacking telomeric signals, were observed with a frequency of about 4-7 times higher than the dicentric frequency. Acentric interstitial fragments and ICE were induced at similar frequencies, except for the lowest BLM concentration (1 microg/ml), where the latter ones showed a higher frequency than the former ones. Furthermore, it was estimated that about 53% of excess acentric fragments originate from complete exchanges (interstitial deletions) and 47% from incomplete exchanges or terminal deletions. These results show that interstitial fragments and ICE are the most frequent asymmetrical chromosomal aberrations induced by BLM and indicate that true incompleteness is a common event following exposure to BLM. Moreover, the comparable trend of the concentration-response relationship for the different aberrations strongly suggests that all BLM-induced asymmetrical aberrations are formed by a similar underlying mechanism.