Immortalization of mutant p53-transfected human fibroblasts by treatment with either 4-nitroquinoline 1-oxide or x-rays

Keiji Kino, Kazuo Fushimi, Chong Gao, Tomoko Shima, Koichiro Mihara, Masayoshi Namba*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


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 273(Arg-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.

Original languageEnglish (US)
Pages (from-to)628-632
Number of pages5
JournalIn Vitro Cellular and Developmental Biology - Animal
Issue number8
StatePublished - Sep 1997


  • 4NQO
  • Human cells
  • Immortalization
  • Mutant p53
  • P16
  • P21
  • X-rays

ASJC Scopus subject areas

  • Cell Biology
  • Developmental Biology


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