Increased Radiosensitivity of CellLines Derived From a Down’s Syndrome Patient With

Studies on radiosensitivity of cells from Down’s syndrome (DS) patients were stimulated by the observation of their in-creased susceptibility to leukemia. While lymphocytes from DS patients were found to consistently show increased chro-mosomal aberrations after exposure to ionizing radiation, conflicting reports have been published on the radiosensitivity of fibroblasts and lymphoblastoid cell lines (LCL) derived from these patients. In the present study, cultured skin fibro-blast lines developed from a DS patient with ocular telangiectasia and five normal subjects were compared for both cell killing and chromosomal aberrations (breaks, translocations, inversions, dicentrics, and rings) after low dose-rate γ-irradiation. The LCLs developed from the patient and two normal persons were also compared for chromosomal radi-osensitivity using the same irradiation protocol. A comparison of the D10 (radiation dose resulting in 10 % survival) values estimated from the survival curves and the frequencies of induced chromosome aberrations in different cell lines showed that the DS cells were more radiosensitive than the respective controls. The increased cellular radiosensitivity of the DS patient reported here could be due to a combination of genetic factors (DS plus a gene for hypersensitivity to radiation) and, thus, may not be representative of all DS patients. Alternatively, the use of low dose-rate irradiation could be a factor in revealing the radiosensitivity of DS fibroblasts in general. (J Child Neurol 1992;7(Suppl):S83-S87.) own syndrome (DS