Enhanced radiotolerance to ionizing radiation is correlated with increased cancer proneness of cultured fibroblasts from precursor states in neurofibromatosis patients.

We have determined the sensitivity to gamma rays of cultured fibroblasts derived from clinically defined areas on the skin of neurofibromatosis patients. Fibroblasts from skin of normal appearance were normally sensitive to gamma irradiation. Significantly, however, fibroblasts from café-au-lait lesions and from neurofibromas were abnormally radiotolerant (about twofold) to treatment with gamma rays. This was seen in specimens taken from the same patient, as well as from different patients, within four different neurofibromatosis pedigrees. In contrast, no differences in radiosensitivity have been observed between fibroblasts derived from skin of normal appearance and those obtained from melanotic freckles of individuals with no family history of cancer. The results suggest that increased propensity to cancer in this cell system is associated with increased radiotolerance to ionizing radiation.