Specificity of Bleomycin-induced Cytotoxic Effects on Ataxia Telangiectasia Lymphoid Cell Lines1

Bleomycin exposure evoked a specific sensitivity in five ataxia telangiectasia (AT) long-term lymphoblastoid cell lines when compared to lines derived from four normal individuals or three patients with xeroderma pigmentosum. At all concen trations tested or after each treatment regimen, statistically significant differences in viability and cytogenetic damage were obvious, with the AT cell lines demonstrating reduced survival and increased chromosomal breakage. However, similar differ ences were not observed following treatment of all cell lines with mitomycin C. The normal and xeroderma pigmentosum cells appear capable of overcoming the effects of bleomycin during a 48or 72-hr recovery period while the AT cell lines could not. This specific response to bleomycin constitutes the first demonstration of increased chromosome breakage in vitro in long-term AT lymphoblastoid cell lines.