THE INFLUENCE OF DNA-PLOIDY OF A HUMAN TUMOR-CELL LINE ON THE FREQUENCIES OF MICRONUCLEI OR CHROMOSOME-ABERRATIONS AFTER IRRADIATION

To develop methods for assessing the intrinsic cellular radiosensitivi ty, it is important to evaluate the relationship between DNA ploidy of cells and frequencies of micronuclei (MN) or chromosome aberrations a fter irradiation. From the original human fibrosarcoma cell line HT-10 80, we isolated two clones which have different chromosome ploidy: clo ne 5 is pseudodiploid and clone 1 is heteroploid, We examined the radi osensitivity of the two clones using a clonogenic cell survival assay and a cytokinesis-block MN assay, and by scoring chromosome aberration s using the premature chromosome condensation (PCC) method combined wi th a fluorescence in situ hybridization (FISH) procedure immediately a nd at 24 h after irradiation. The MN frequency increased according to the irradiation dose in both clones. The MN frequency of clone 1 was s ignificantly higher than that of clone 5 regardless of whether the ass ay was performed immediately or 24 h after irradiation. However, when the numbers of MN were normalized by the DNA index of each clone, a si gnificant difference in the frequency of MN was not observed. In the P CC and FISH studies, there was a linear relationship between the radia tion dose and the initial breaks of chromosome 4, but the breaks of cl one 1 were much more frequent than those of clone 5. Twenty-four h aft er irradiation, the chromosome 4 breaks of clone 1 were observed much more frequently than those of clone 5 at the same radiation dose. When the numbers of chromosome 4 breaks were normalized by the number of c hromosome 4 in each clone without radiation, no such difference in the number of breaks was observed. These findings demonstrated that the D NA content or chromosome ploidy influenced the induction of the MN or chromosome aberrations in HT-1080 cells after irradiation. (C) 1998 El sevier Science B,V. All rights reserved.