| Tumor development is a multi-step processes during which genetic events determine the transition from normal to malignant cellular state. Human cell transformation model of tumorigenesis has been instrumental in investigating mechanism underling cellular progression from normal to malignant in vivo.Epidemiological studies have shown that underground miners exposed to high levels of radon a-particles have increased risk of lung cancers. Domestically, exposure to radon and its progenies represents the biggest involuntary environmental hazard. About 50% of average annual effective dose of natural irradiation resulted from a-particles emitted by radon and its progeny products. The cellular and molecular mechanisms for radon-induced carcinogenesis are not clear. So the importance is attached to the relationship between a-particles and lung cancers. Now a series of animal carcinogenic experiments and in vitro oncogenic transformation of fibroblast cells induced by a-particles have been reported. But it will be ideal to use a human bronchial epithelial cell line that has been malignantly transformed by a-particles to assess the various changes related with malignancies, because about 80% of human cancers arise from epithelial cells of different tissues.Series studies including transformation of immortalized human bronchial epithelial cell line(BEP2D)by a-particles, and cytogenetic and molecular analysis have been performed in our laboratory in order to understand the mechanism responsible for cell transformation and tumorigenesis induced by a-particles.The tumorigenic potential of BERP35T4 was investigated based on the previous research results. Three cell lines (BERP35T4-Ta BERP35T4-Tb BERP35T4-Tc) were derived from tumor tissues developed in nude mice which were injected subcutaneously with the BERP35T4 cells. The biological characteristics, chromosomaland molecular changes of BERP35T4-Ta were investigated in this study. The main results are as follows:1. The transformed human bronchial epithelial cells BERP35T4 were inoculated subcutaneously (SC) into 5-6 weeks old BALB/C nude mice. The human papillomavirus 18 (HPV18) immortalized human bronchial epithelial cell line BEP2D was used as control. After 16 weeks, 4 of 9 nude mice inoculated with BERP35T4 cells developed tumors, and one of of them presented subcutaneous and lung metastasis, while no tumors were formed in the 9 control animals. The tumor nodules developed from the nude mice were passaged for 3 times in nude mice via orthotopic implantation of histologically intact tissues and all of the nude mice developed tumors. Histopathological analysis, electron micrograph and immunohistochemical staining of CK3 and EMA revealed that the tumors were squamous epithelial carcinoma with low differentiation. The results suggest that the BEP2D cells neoplasticly transformed by a-particles have the tumorigenic potential in nude mice.2. Using the immortalized human bronchial epithelial cell line BEP2D and the transformed human bronchial epithelial cells BERP35T4 as control, the dynamics of proliferation anchorage independence growths the resistance to serum-induced terminal differentiation cytological morphormet the chromosome changes and the mobility of BERP35T4-Ta cells were studied. The results indicate that the proliferation rate of BERP35T4-Ta cells is higher than that of BEP2D and BERP35T4 cells. The anchorage independence growth ability and the resistance to serum-induced terminal differentiation of BERP35T4-Ta cells were stronger than that of BEP2D and BERP35T4 cells. The cytological morphormetry study shows that the cellular and nuclear area of BERP35T4-Ta was significantly increased, while the nucleus/cytoplasm ratio was increased too. Chromosome changes of BERP35T4-Ta cells were analyzed by G-banding technique. The results were as follows: the chromosomal number of BEP2D cells was maintained at near diploid, but there was a shift for BERP35T4-Ta from near diploid toward poly-ploi... |
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