DETECTION OF RADIATION-INDUCED CHROMOSOME-ABERRATIONS USING FLUORESCENCE IN-SITU HYBRIDIZATION IN DRUG-INDUCED PREMATURE CHROMOSOME CONDENSATIONS OF TUMOR-CELL LINES WITH DIFFERENT RADIOSENSITIVITIES

A potential assay for radiosensitivity of human tumours is that of rad iation-induced chromosome damage determined on metaphase spreads of hu man solid tumours. It is often difficult, however, to obtain enough me taphases for cytogenetic analysis after radiation. A possible solution would be to use the technique of premature chromosome condensation (P CC), enabling the study of interphase cells. The induction of PCCs usi ng mitotic inducer cells is technically difficult, however, and the fr equency of induction relatively low. We have attempted to use another approach to induce PCCs using the phosphatase inhibitors okadaic acid and calyculin A. Both inhibitors were found to induce PCCs in several human tumour cell. lines, with calyculin A producing the higher incide nce. Determination of radiation-induced chromosome aberrations using f luorescence in situ hybridization on these chemically induced PCCs sho wed a clear difference between a radiosensitive (SCC61) and a radiores istant (A549) tumour cell line, with more aberrations in the sensitive line. Owing to incomplete condensation compared with that in standard metaphases, accurate classification of aberration types was not possi ble. Despite this limitation, the present data indicate that this rela tively quick and simple method may be useful for determining chromosom e aberrations in interphase cells and potentially in human solid rumou rs for predictive assay purposes.