[Aging and immortalization of human cells]

Area of Science:

• Cell biology
• Carcinogenesis research
• Molecular oncology

Background:

• Malignant transformation of human cells in vitro is crucial for understanding multistep carcinogenesis.
• Normal human cells are resistant to immortalization, a prerequisite for malignant transformation, making it a rate-limiting step.
• Previous studies indicated multiple mutations are involved in the multi-step immortalization process.

Purpose of the Study:

• To investigate the role of the p53 gene in the immortalization and malignant transformation of human cells.
• To determine if introducing mutant p53 can overcome the refractory nature of normal human cells to immortalization.
• To explore the synergistic effects of mutant p53 and chemical carcinogens in cellular immortalization.

Main Methods:

• Normal human fibroblasts were introduced with a specific mutant p53 (codon 273Arg-His).
• Cells were treated with 4-nitroquinoline 1-oxide (4NQO) alone or in combination with mutant p53.
• Cell lifespan extension and immortalization were monitored following treatments.

Main Results:

• Introduction of mutant p53 alone extended the lifespan of human fibroblasts but did not cause immortalization.
• Combined treatment of 4NQO and mutant p53 successfully immortalized the human fibroblasts.
• 4NQO treatment alone did not result in immortalization, indicating a crucial role for p53 in this process.

Conclusions:

• The p53 gene plays a significant role in the immortalization of human cells.
• Mutant p53 facilitates the immortalization process, particularly when combined with carcinogen exposure.
• These findings suggest p53 is more critical for immortalization than for the subsequent malignant transformation step.