Re-evaluation ofin VitroRadiosensitivity of Human Fibroblasts of Different Genetic Origins

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Abstract
A statistical analysis of the radiosensitivity of 204 different survival curves of nontransformed human fibroblast cell strains of different genetic origins was made using three criteria: the multi-target one-hit model (characterized by parameters n and DO), the surviving fraction for a 2 Gy dose (S2) and the mean inactivation dose (.hivin.D). .hivin.D is found to be the best parameter for characterization of anomalous radiosensitivity linked to a genetic disorder and for discrimination between groups of cell strains of differing radiosensitivity. Its use allows the description of a range of ''normal'' radiosensitivity for control fibroblasts and the classification of the various genetic disorders as a function of their mean radiosensitivity expressed in terms of .ovrhdot.D. Nine groups of cell strains appear to exhibit radiosensitive (ataxia-telangiectasia homozygotes and heterozygotes, Cockayne''s syndrome, Gardner''s syndrome, 5-oxoprolinuria homozygotes and heterozygotes, Fanconi''s anaemia) and two groups are more radioresistant (fibroblasts from retinoblastoma patients and from individuals with chromosome 13 anomalies). Since the coupled parameter n and DO failed to discriminate between the radiosensitivity of the different genetic groups, we recommend the use of .hivin.D to make an intercomparison of intrinsic radiosensitivity of nontransformed human fibroblasts.