FHIT Protein Expression And Chromosome Aberration During Malignant Transformation Of Human Bronchial Epithelial Cells Induced By NNK

Objective To investigate FHIT protein expression and 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 FHIT protein expression and chromosome aberration were detected in the different passage of BEAS-2BNNK and BEAS-2B cells by Sp immunocytochemistry and count of metaphase chromosome .Results 1. Model of malignant transformation of BEAS-2B cells induced by NNK was created ①The serum resistance was significantly increased in the 5th passage BEAS-2BNNK cells. ②The anchorage independent growth(soft agar colony formation)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 aneuploid cells increased in process of passing generation. There was 3% of endoreduplications in the 25th passage of BEAS-2BNNK cells. ② The ratio of unstable aberration neared to 2%-4% in BEAS-2BNNK and BEAS-2B cells but the 25th passage of BEAS-2BNNK cells was 11%. 3. FHIT protein expression FHIT protein steadily expressed in the different passages of BEAS-2B cells. FHIT protein expression had been decreasing from 5th to 15th passage of BEAS-2BNNK cells, but there was unexpectedly overexpression of FHIT protein in the 25th passage. Conclusion 1. The model of malignant transformation of BEAS- 2B cells induced by NNK(500μɡ/ml) could be created successfully and provided for investigating the molecular biological mechanism of lung cancer, especially smoking-related cases. 2. The polyploid and aneuploid chromosomes could be the early event in the process of malignant transformation of BEAS-2B cells induced by NNK. Endoreduplication might be the causes of the polyploid and aneuploid chromosomes. 3. It was suggerted an early event that FHIT protein expression decreased in earlier passages. Overexpression of FHIT protein in the late passages should be further studied. In a word, the chromosome aberration and FHIT protein expression might be useful markers for the early-warning and mass screening of lung cancer, especially in high-risk smoking population.