Objective To investigate chromosome aberration during malignant transformation of immortalized human bronchial epithelial cells ( BEAS - 2B) induced by tobacco specific nitrosamine ( NNK)

and explore those significance of early - warning and mass screening of lung cancer in high - risk smoking population. Methods Immortalized human bronchial epithelial cells ( BEAS - 2B) were induced to malignant transformation cells ( BEAS - 2BNNK ) by NNK

and chromosome aberration were detected in the different passage of BEAS - 2BNNK and BEAS - 2B cells by analysis of metaphase chromosome. Results 1. Model of malignant transformation of BEAS -2B cells induced by NNK was created (1)The serum resistance was significantly increased in the 5th passage BEAS - 2BNNK cells.(2) The anchorage independent growth was appeared in the 15th passage. (3)The ultrastructure of the 20th passage BEAS - 2BNNK cells shown obvious heteromorphy characterization. (4)The 25th passage BEAS -2BNNK cells formed tumors in nude mice

and tumors were overdifferentiation squamous cell carcinoma confirmed by histopathological examination. 2. Chromosome aberration (1) BEAS -2B cells hold relatively stable diploid karyotype which ratio was 91%-97% up to the 25th passage. Different passage BEAS -2BNNK cells gradually lost the normal diploid karyotype and the ratio of diploid cells decreased from 83% to 54%

the proportion of polyploid and aneu-ploid cells increased in process of passing generation. (2)The ratio of structure aberration neared to 2% ~ 4% in BEAS - 2BNNK and BE-AS -2B cells but the 25th passage of BEAS -2BNNK cells was 11%. Conclusion The model of malignant transformation of BEAS - 2B cells induced by NNK could be created successfully and provided for investigating the molecular biological mechanism of lung cancer

especially smoking - related cases. The polyploid and aneuploid chromosomes could be the early event in the process of malignant transformation of BEAS - 2B cells induced by NNK. In a word

the chromosome aberration might be useful markers for the early warning and mass screening of lung cancer

especially in high - risk smoking population.