CHROMOSOME ANALYSIS IN X-IRRADIATED PRIMARY-CELLS OF A HUMAN SQUAMOUS-CELL CARCINOMA BY FLUORESCENCE IN-SITU HYBRIDIZATION

Chromosomes in primary tumour cells derived from a squamous cell carci noma of the gingival mucosa were analysed. The ploidy of individual ch romosomes and the frequencies of reciprocal translocations in unirradi ated and irradiated cells were assessed by the method of fluorescence in situ hybridization. Hybridization probes for whole chromosomes 1, 2 , 3, 4, 9 and 12 were used. The analysis was carried out in early (1st -3rd) passage cells and for comparison, in late (25th-30th) passage ce lls. A radiation-induced polyploidy of all analysed chromosomes was ob served in irradiated (D = 4 Gy) early as well as late passage cells, w ith the exception of chromosome 4 in late passage cells. Ploidy of chr omosomes 1 and 4 was studied at lower doses (1-3 Gy), too. Polyploidy was observed for doses >2 Gy. Some of the analysed chromosomes showed a high 'spontaneous' translocation frequency in both types of cells. T he frequencies of radiation-induced translocations were similar in ear ly and late cells and these frequencies were not always proportional t o the length of the chromosomes studied. The radiosensitivity of indiv idual chromosomes was not correlated with the level of spontaneous tra nslocation frequency.