HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

J. Biol. Chem., Vol. 279, Issue 42, 43634-43645, October 15, 2004

This Article Full Text Full Text (PDF) All Versions of this Article: 279/42/43634    most recent M402388200v1 Submit a Letter to Editor Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Taylor, L. M. Articles by MacKenzie, K. L. Search for Related Content PubMed PubMed Citation Articles by Taylor, L. M. Articles by MacKenzie, K. L. Social Bookmarking                      What's this?

Inactivation of p16^INK4a, with Retention of pRB and p53/p21^cip1 Function, in Human MRC5 Fibroblasts That Overcome a Telomere-independent Crisis during Immortalization^*

Lisa M. Taylor, Alexander James, Christine E. Schuller, Jesena Brce, Richard B. Lock, and Karen L. MacKenzie

From the Children's Cancer Institute Australia for Medical Research, Randwick, New South Wales 2031, Australia

Recent investigations, including our own, have shown that specific strains of fibroblasts expressing telomerase reverse transcriptase (hTERT) have an extended lifespan, but are not immortal. We previously demonstrated that hTERT-transduced MRC5 fetal lung fibroblasts (MRC5hTERTs) bypassed senescence but eventually succumbed to a second mortality barrier (crisis). In the present study, 67 MRC5hTERT clones were established by limiting dilution of a mass culture. Whereas 39/67 clones had an extended lifespan, all 39 extended lifespan clones underwent crisis. 11 of 39 clones escaped crisis and were immortalized. There was no apparent relationship between the fate of clones at crisis and the level of telomerase activity. Telomeres were hyperextended in the majority of the clones analyzed. There was no difference in telomere length of pre-crisis compared with post-crisis and immortal clones, indicating that hyperextended telomeres were conducive for immortalization and confirming that crisis was independent of telomere length. Immortalization of MRC5hTERT cells was associated with repression of the cyclin-dependent kinase inhibitor p16^INK4a and up-regulation of pRB. However, the regulation of pRB phosphorylation and the response of the p53/p21^cip1/waf1 pathway were normal in immortal cells subject to genotoxic stress. Overexpression of oncogenic ras failed to de-repress p16^INK4a in immortal cells. Furthermore, expression of ras enforced senescent-like growth arrest in p16^INK4a-positive, but not p16^INK4a-negative MRC5hTERT cells. Immortal cells expressing ras formed small, infrequent colonies in soft agarose, but were non-tumorigenic. Overall, these results implicate the inactivation of p16^INK4a as a critical event for overcoming telomere-independent crisis, immortalizing MRC5 fibroblasts and overcoming ras-induced premature senescence.

Received for publication, March 3, 2004 , and in revised form, August 9, 2004.

^* This work was supported by grant funds from the Concern Foundation and the University of New South Wales Research Support Program. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

To whom correspondence should be addressed: Children's Cancer Institute Australia for Medical Research, P. O. Box 81 High St., Randwick, NSW 2031, Australia. Tel.: 61-2-9382-0048; Fax: 61-2-9382-1850; E-mail: k.mackenzie{at}unsw.edu.au.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				T. Nyunoya, M. M. Monick, A. Klingelhutz, T. O. Yarovinsky, J. R. Cagley, and G. W. Hunninghake Cigarette Smoke Induces Cellular Senescence Am. J. Respir. Cell Mol. Biol., December 1, 2006; 35(6): 681 - 688. [Abstract] [Full Text] [PDF]

				V. W. Wen, K. Wu, S. Baksh, R. A. Hinshelwood, R. B. Lock, S. J. Clark, M. A.S. Moore, and K. L. MacKenzie Telomere-Driven Karyotypic Complexity Concurs with p16INK4a Inactivation in TP53-Competent Immortal Endothelial Cells. Cancer Res., November 15, 2006; 66(22): 10691 - 10700. [Abstract] [Full Text] [PDF]

				S.-H. Kim, J. Rowe, H. Fujii, R. Jones, B. Schmierer, B.-W. Kong, K. Kuchler, D. Foster, D. Ish-Horowicz, and G. Peters Upregulation of chicken p15INK4b at senescence and in the developing brain J. Cell Sci., June 15, 2006; 119(12): 2435 - 2443. [Abstract] [Full Text] [PDF]

				I. Kogan, N. Goldfinger, M. Milyavsky, M. Cohen, I. Shats, G. Dobler, H. Klocker, B. Wasylyk, M. Voller, T. Aalders, et al. hTERT-Immortalized Prostate Epithelial and Stromal-Derived Cells: an Authentic In vitro Model for Differentiation and Carcinogenesis. Cancer Res., April 1, 2006; 66(7): 3531 - 3540. [Abstract] [Full Text] [PDF]

				S. Zongaro, E. de Stanchina, T. Colombo, M. D'Incalci, E. Giulotto, and C. Mondello Stepwise Neoplastic Transformation of a Telomerase Immortalized Fibroblast Cell Line Cancer Res., December 15, 2005; 65(24): 11411 - 11418. [Abstract] [Full Text] [PDF]

				M. Milyavsky, Y. Tabach, I. Shats, N. Erez, Y. Cohen, X. Tang, M. Kalis, I. Kogan, Y. Buganim, N. Goldfinger, et al. Transcriptional Programs following Genetic Alterations in p53, INK4A, and H-Ras Genes along Defined Stages of Malignant Transformation Cancer Res., June 1, 2005; 65(11): 4530 - 4543. [Abstract] [Full Text] [PDF]