RECIPROCAL TRANSLOCATION FREQUENCY IN IRRADIATED SENSITIVE AND RESISTANT HUMAN TUMOR-CELLS IN CORRELATION WITH CLONOGENIC IN-VITRO CELL-SURVIVAL - A POSSIBILITY OF TUMOR RADIOSENSITIVITY PREDICTION

We have investigated the yields of radiation-induced translocations in several human tumor cell lines and in normal diploid human fibroblast s by fluorescence in situ hybridization. The translocation yields were determined with respect to chromosome no. 1 in all cell lines investi gated, and moreover in chromosomes nos. 2, 4 and 9 in fibroblasts and one tumor cell line. The chromosomes were 'painted' with fluorescent w hole chromosome-hybridization probes. The clonogenic survival of the s tudied cell lines was determined by standard colony-formation assay. W e observed a higher frequency of reciprocal translocations in the radi osensitive cells MCF-7 and MDA-MB-436 as compared with the radioresist ant cells CaSki and normal skin fibroblasts. Thus, the results suggest a possibility to predict the intrinsic tumor radiosensitivity on the basis of reciprocal translocation yield determined in cells irradiated in vitro. The correlation was observed in spite of the trisomy no. 1 which occurred in all three investigated tumor cell lines. On the othe r hand, the results obtained with different chromosomes in MCF-7 cells suggest that only chromosomes with relatively low 'spontaneous' trans location yields are suitable for this kind of analysis.