Biological and Molecular Studies on Aging and Immortalization of Human Cells

正常的人类细胞注定会发生细胞衰老。阐明细胞衰老的机制将有助于揭示人类细胞恶性转化的多步骤过程。为了克服衰老并使正常人类细胞永生，我们不得不用4NQO或Co-60伽马射线反复处理细胞。这表明永生化过程涉及多步突变事件。我们获得的三个永生化细胞系均显示P53基因发生突变，提示P53基因可能参与了人类细胞的衰老和永生化过程，因此我们将突变型P53基因导入正常人细胞中，以了解细胞是否可以永生化。突变型p53延长了细胞的寿命，但不能使它们永生。然而，用4NQO或X射线将P53基因导入的细胞永生化。用这些试剂对细胞进行相同的处理并没有使细胞永生。我们的其他实验表明，永生化细胞系中SDII表达下调，cdc2、CDK4和myc表达增强。这些结果表明，细胞衰老/永生化受与细胞生长相关的负性和正性调控基因的控制。

Normal human cells are strongly destined for cellular aging. Elucidation of the mechanisms of cellular aging will shed light on the multistep processes of malignant transformation of human cells.In order to overcome aging and to immortalize normal human cells, we had to treat the cells repeatedly with either 4NQO or Co-60 gamma rays. This indicates that the immortalization process involves multistep mutational events. The three immortalized cell lines we obtained showed mutation in p53, indicating that p53 may be involved in aging and immortalization process of human cells.Thus we introduced the mutant p53 into normal human cells to learn whether or not the cells could be immortalized. The mutant p53 extended the life-span of the cells but could not immortalize them. However, the cells into which the p53 had been introduced were immortalized with 4NQO or x-rays. The identical treatment of the cells with these agents did not make the cells immortal. These results demonstrate that p53 can play a role in aging/immortalization of human cells.Our other experiments showed downregulation of SdiI and enhanced expression of cdc2, cdk4, and myc in the immortalized cell lines. These results indicate that cellular aging/immortalization is controlled by both negatively and positively regulating genes related to cell growth.