Abstract: Purpose : To subclone the malignant transformants of human bronchial epithelial cell line (BEP2D) induced byα-particles and to analyse their karyotypes and capacity of rejoining DNA double-strand breaks (DSB) . Methods :Tumor cells were isolated from nude mice bearing malignant transformed cells(passage 35 cells of 1. 5 Gy ofα-articles- irradiated BEP2D and were subcloned in vitro. Trypsin/ Giemsa banding of chromosomes and pulsed field gel electrophoresis were used to analyse karyotypes and DNA repair respectively. Results : Five individual malignant transformed cell lines (RP35T21 ,22 ,24 ,25 ,26) were subcloned. Multi-locus chromosome deletions were shown in these malignant transformed cell lines as well as the parental line BEP2D. The ratio of polyploids of RP35T22 and RP35T24 cells was about 40 % and was higher than that of PEB2D cells(5 %) , The other three lines showed the same polyploid levels as the parental cell line. The capacity of rejoining DSB in RP35T21 and RP35T24 cell lines was obviously deficient. Conclusion : Five malignant transformed cell lines were subcloned. The deficiency of DNA DSB repair could be an important characteristic ofα-particle-induced carcinogenesis.

Key words: human bronchial epithelial cell, α-particle, carcinogenesis, karyotype, DNA repair