G2 chromosomal sensitivity to bleomycin (30 micrograms/ml) was tested in PHA-stimulated lymphocytes of healthy subjects and in patients with familial and sporadic tumors. These were multiple endocrine neoplasias (MEN) types 1, 2A and 2B, familial medullar thyroid cancer, Recklinghausen neurofibromatosis type I, sporadic and hereditary malignant tumors, and a preleukemic disorder, the myelodysplastic syndrome. Control subjects were either young (15-20), middle-aged (28-49) or old (70-83 years). Cells from old healthy subjects and from subjects with MEN 1 showed increased sensitivity to clastogenic effects of bleomycin. All the remaining investigated groups were insignificantly different from controls. Our data suggest that in contrast with recessively inherited syndromes with chromosome instability the mutagen hypersensitivity, as evaluated by the extent of chromosomal damage, is not a feature of most dominantly inherited tumor syndromes.

3rd Medical Department 1st Medical Faculty Charles University Prague Czech Republic