Telomerase upregulation is a postcrisis event during senescence bypass and immortalization of two Nijmegen breakage syndrome T cell cultures

Degerman, S., Siwicki, J. K., Osterman, P., Lafferty-Whyte, K., Keith, W.N. and Roos, G. (2010) Telomerase upregulation is a postcrisis event during senescence bypass and immortalization of two Nijmegen breakage syndrome T cell cultures. Aging Cell, 9(2), pp. 220-235. (doi:10.1111/j.1474-9726.2010.00550.x)

Full text not currently available from Enlighten.

Abstract

Our knowledge on immortalization and telomere biology is mainly based on genetically manipulated cells analyzed before and many population doublings post growth crisis. The general view is that growth crisis is telomere length (TL) dependent and that escape from crisis is coupled to increased expression of the telomerase reverse transcriptase (hTERT) gene, telomerase activity upregulation and TL stabilization. Here we have analyzed the process of spontaneous immortalization of human T cells, regarding pathways involved in senescence and telomerase regulation. Two Nijmegen breakage syndrome (NBS) T cell cultures (S3R and S4) showed gradual telomere attrition until a period of growth crisis followed by the outgrowth of immortalized cells. Whole genome expression analysis indicated differences between pre-, early post- and late postcrisis cells. Early postcrisis cells demonstrated a logarithmic growth curve, very short telomeres and, notably, no increase in hTERT or telomerase activity despite downregulation of several negative hTERT regulators (e. g. FOS, JUN D, SMAD3, RUNX2, TNF-alpha and TGF beta-R2). Thereafter, cMYC mRNA increased in parallel with increased hTERT expression, telomerase activity and elongation of short telomeres, indicating a step-wise activation of hTERT transcription involving reduction of negative regulators followed by activation of positive regulator(s). Gene expression analysis indicated that cells escaped growth crisis by deregulated DNA damage response and senescence controlling genes, including downregulation of ATM, CDKN1B (p27), CDKN2D (p19) and ASF1A and upregulation of CDK4, TWIST1, TP73L (p63) and SYK. Telomerase upregulation was thus found to be uncoupled to escape of growth crisis but rather a later event in the immortalization process of NBS T cell cultures.

Item Type:Articles
Keywords:Aging Apoptosis B-CELLS BIOLOGY CANCER CELLS CHRONIC LYMPHOCYTIC-LEUKEMIA CULTURE DNA DNA-DAMAGE EXPRESSION GENE GENE-EXPRESSION growth hTERT HTERT GENE Human HUMAN CANCER-CELLS immortalization INCREASE PATHWAY POPULATION REDUCTION senescence T cells T-cell T-CELLS telomerase telomere TELOMERE LENGTH TGF-BETA TRIGGERS SENESCENCE TUMOR SUPPRESSION TYROSINE KINASE
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Keith, Professor Nicol
Authors: Degerman, S., Siwicki, J. K., Osterman, P., Lafferty-Whyte, K., Keith, W.N., and Roos, G.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cancer Sciences
Journal Name:Aging Cell
ISSN:1474-9718
ISSN (Online):1474-9726
Published Online:18 January 2010

University Staff: Request a correction | Enlighten Editors: Update this record