Cellular hypersensitivity to neocarzinostatin in ataxia-telangiectasia skin fibroblasts.

Cellular sensitivity of human skin fibroblast strains from three healthy donors, eight ataxia-telangiectasia (A-T) patients belonging to six sibships, and two A-T heterozygotes to the lethal action of the antitumor antibiotic neocarzinostatin was tested, using colony-forming ability as the criterion for survival. All the A-T strains were significantly more sensitive to killing by neocarzinostatin than were the control strains. The average D0 for the A-T strains following neocarzinostatin treatment was 14.6 ng/ml, as compared to 37.9 ng/ml for the normal strains. The two A-T heterozygous strains showed intermediate sensitivity with an average D0 of 26.9 ng/ml. Neocarzinostatin sensitivity of A-T cells could therefore serve as a convenient aid for the laboratory diagnosis of A-T. Since A-T cells are also known to be hypersensitive to ionizing radiation and bleomycin, it would appear that they are primarily hypersensitive to DNA-breaking agents.