G(2) CHROMOSOMAL RADIOSENSITIVITY IN FIBROBLASTS OF ATAXIA-TELANGIECTASIA HETEROZYGOTES AND A LI-FRAUMENI-SYNDROME PATIENT WITH RADIORESISTANT CELLS

Purpose: To investigate whether the good discrimination ive previously observed between ataxia-telangiectasia (A-T) heterozygotes and normal donors for induction of chromosome aberrations by X-rays in G(2) lymp hocytes is also seen in G(2) fibroblasts. Also to investigate the G(2) radiosensitivity of a patient with the cancer-prone Li-Fraumeni syndr ome (LFS) whose fibroblasts are resistant to the lethal effects of rad iation. Materials and methods: Fibroblasts were exposed to 0.5 Gy X-ra ys and harvested for metaphase analysis 90 min later. Results: Four A- T heterozygote cell strains were all more sensitive than seven normal controls. The LFS strain with a germline TP53 mutation was twice as se nsitive as the mean control value. Conclusions: Although chromosomal r adiosensitivity is seen in A-T heterozygotes and LFS cells, the former are radiosensitive and the latter radioresistant to cell killing. Rep air defects may predominate in A-T heterozygotes, inadequate genome su rveillance in LFS cells.