Immortalization of mutant p53-transfected human fibroblasts by treatment with either 4-nitroquinoline 1-oxide or x-rays |
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Authors: | Keiji Kino Kazuo Fushimi Chong Gao Tomoko Shima Koichiro Mihara Masayoshi Namba |
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Institution: | (1) Department of Cell Biology, Institute of Cellular and Molecular Biology, Okayama University Medical School, 2-5-1 Shikata, 700 Okayama;(2) Department of Genetics, Hyogo College of Medicine, 1-1 Mukogawa, Nishinomiya, 663 Hyogo, Japan |
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Abstract: | Summary The study of in vitro cell transformation is valuable for understanding the multistep carcinogenesis of human cells. The difficulty in inducing
neoplastic transformation of human cells by treatment with chemical or physical agents alone is due to the difficulty in immortalizing
normal human cells. Thus, the immortalization step is critical for in vitro neoplastic transformation of human cells. We transfected a mutant p53 gene (mp53: codon 273Arg-His) into normal human fibroblasts and obtained two G418-resistant mp53-containing clones. These clones showed an extended life
span but ultimately senesced. However, when they were treated with either 4-nitroquinoline 1-oxide or X rays, they were immortalized.
The immortalized cells showed both numerical and structural chromosome abnormalities, but they were not tumorigenic. The expression
of mutant but not wild type p53 was detected in the immortalized cells by RT-PCR. Expression of p21, which is located downstream
of p53, was remarkably reduced in the immortalized cells, resulting in increased cdk2 and cdc2 kinase activity. However, there
was no significant difference between the normal and immortalized human cells in expression of another tumor suppressor gene,
p16. These findings indicate that the p53-p21 cascade may play an important role in the immortalization of human cells. |
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Keywords: | immortalization human cells mutant p53 4NQO X-rays p21 p16 |
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