Increased level of bleomycin-induced chromosome breakage in ataxia telangiectasia skin fibroblasts.

Ataxia telangiectasia (AT) is an autosomal recessive disorder in which increased level of chromosome breakage and specific sensitivity to radiation and carcinogens have been reported. The effect of the radiomimetic drug bleomycin on chromosome breakage has been tested in skin fibroblasts of three patients with AT, two AT obligate heterozygotes, two normal human controls, and one normal amniotic fluid cell culture. Bleomycin in two concentrations (1 and 5 micrograms/ml) was added for 1 hr and cultures were harvested 4 hr later. A significant increase in chromosome damage was found in AT fibroblasts: a higher number of total breaks per cell, affected cells, and breaks per affected cell was found. The heterozygotes did not differ significantly from the controls. Chromosome breakage in skin fibroblasts of AT patients after bleomycin treatment has not been reported before.