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Both Rb/p16INK4a inactivation and telomerase activity are required to immortalize human epithelial cells

Nature volume 396, pages 84–88 (1998)Cite this article

Abstract

Normal human cells undergo a limited number of divisions in culture and enter a non-dividing state called replicative senescence1. Senescence is accompanied by several changes, including an increase in inhibitors of cyclin-dependent kinases2,3 and telomere shortening4. The mechanisms by which viral oncogenes reverse these processes are not fully understood, although a general requirement for oncoproteins such as human papillomavirus E6 and E7 has suggested that the p53 and Rb pathways are targeted. Expression of the catalytic component of telomerase, hTERT, alone significantly extends the lifespan of human fibroblasts5. Here we show that telomerase activity is not sufficient for immortalization of human keratinocyte or mammary epithelial cells: we find that neither addition of hTERT nor induction of telomerase activity by E6, both of which are active in maintaining telomere length, results in immortalization. Inactivation of the Rb/p16 pathway by E7 or downregulation of p16 expression, in combination with telomerase activity, however, is able to immortalize epithelial cells efficiently. Elimination of p53 and of the DNA-damage-induced G1 checkpoint is not necessary for immortalization, neither is elimination of p19ARF.

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Figure 1: Telomerase activity and telomere length.
Figure 2: Inactivation of the Rb/p16INK4A pathway.
Figure 3: E6 immortalization does not require inactivation of p53.

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Acknowledgements

We thank the Geron Corporation for the hTERT cDNA, E. Espling for maintaining stocks of retroviruses, the Image Analysis Laboratory for help with preparing figures, and members of the McDougall and Galloway laboratories for discussion. This work was supported by grants from the NIH to J.K.M. and D.A.G.

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Author notes

  1. Tohru Kiyono: On leave from the Laboratory of Viral Oncology, Research Institute, Aichi Cancer Center, Nagoya 464, Japan.

Authors and Affiliations

  1. Cancer Biology Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N., Cl-015, PO Box 19024, Seattle, 98109-1024, Washington, USA

    Scott A. Foster, Jenn I. Koop, James K. McDougall, Denise A. Galloway & Aloysius J. Klingelhutz

Authors
  1. Tohru Kiyono
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  2. Scott A. Foster
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  3. Jenn I. Koop
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  5. Denise A. Galloway
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  6. Aloysius J. Klingelhutz
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Correspondence to Denise A. Galloway.

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Kiyono, T., Foster, S., Koop, J. et al. Both Rb/p16INK4a inactivation and telomerase activity are required to immortalize human epithelial cells. Nature 396, 84–88 (1998). https://doi.org/10.1038/23962

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