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Cell Cycle, Cell Death, and Senescence

Genes Involved in Differentiation, Stem Cell Renewal, and Tumorigenesis Are Modulated in Telomerase-Immortalized Human Urothelial Cells

¹ Cancer Research UK Clinical Centre, Leeds Institute of Molecular Medicine, St. James's University Hospital, Leeds, United Kingdom and ² Bioinformatics and Biostatistics Service, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, London, United Kingdom

Requests for reprints: Margaret A. Knowles, Cancer Research UK Clinical Centre, St. James's University Hospital, Beckett Street, Leeds LS97TF, United Kingdom. Phone: 44-11320-64913; Fax: 44-11324-29886. E-mail: m.a.knowles{at}leeds.ac.uk

The expression of hTERT, the catalytic subunit of telomerase, immortalizes normal human urothelial cells (NHUC). Expression of a modified hTERT, without the ability to act in telomere maintenance, did not immortalize NHUC, confirming that effects at telomeres are required for urothelial immortalization. Previous studies indicate that inhibition of telomerase has an immediate effect on urothelial carcinoma (UC) cell line viability, before sufficient divisions to account for telomere attrition, implicating non–telomere effects of telomerase in UC. We analyzed the effects of telomerase on gene expression in isogenic mortal and hTERT-transduced NHUC. hTERT expression led to consistent alterations in the expression of genes predicted to be of phenotypic significance in tumorigenesis. A subset of expression changes were detected soon after transduction with hTERT and persisted with continued culture. These genes (NME5, PSCA, TSPYL5, LY75, IGFBP2, IGF2, CEACAM6, XG, NOX5, KAL1, and HPGD) include eight previously identified as polycomb group targets. TERT-NHUC showed overexpression of the polycomb repressor complex (PRC1 and PRC4) components, BMI1 and SIRT1, and down-regulation of multiple PRC targets and genes associated with differentiation. TERT-NHUC at 100 population doublings, but not soon after transduction, showed increased saturation density and an attenuated differentiation response, indicating that these are not acute effects of telomerase expression. Some of the changes in gene expression identified may contribute to tumorigenesis. Expression of NME5 and NDN was down-regulated in UC cell lines and tumors. Our data supports the concept of both telomere-based and non–telomere effects of telomerase and provides further rationale for the use of telomerase inhibitors in UC. (Mol Cancer Res 2008;6(7):1154–68)