Chapman Emma J, Kelly Gavin, Knowles Margaret A
Cancer Research UK Clinical Centre, St. James's University Hospital, Leeds LS97TF, United Kingdom.
Mol Cancer Res. 2008 Jul;6(7):1154-68. doi: 10.1158/1541-7786.MCR-07-2168.
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.
端粒酶的催化亚基hTERT的表达可使正常人尿路上皮细胞（NHUC）永生化。一种无端粒维持功能的修饰型hTERT的表达未能使NHUC永生化，证实端粒处的作用是尿路上皮细胞永生化所必需的。先前的研究表明，在端粒磨损所需的足够分裂之前，端粒酶抑制对尿路上皮癌（UC）细胞系活力具有直接影响，这暗示了端粒酶在UC中的非端粒效应。我们分析了端粒酶对同基因的原代和hTERT转导的NHUC基因表达的影响。hTERT表达导致预测在肿瘤发生中具有表型意义的基因表达发生一致改变。在用hTERT转导后不久就检测到一部分表达变化，并随着持续培养而持续存在。这些基因（NME5、PSCA、TSPYL5、LY75、IGFBP2、IGF2、CEACAM6、XG、NOX5、KAL1和HPGD）包括8个先前被鉴定为多梳蛋白组靶标的基因。TERT-NHUC显示多梳蛋白抑制复合物（PRC1和PRC4）组分BMI1和SIRT1的过表达，以及多个PRC靶标和与分化相关基因的下调。100次群体倍增时的TERT-NHUC，但不是转导后不久，显示饱和密度增加和分化反应减弱，表明这些不是端粒酶表达的急性效应。所鉴定的一些基因表达变化可能有助于肿瘤发生。NME5和NDN的表达在UC细胞系和肿瘤中下调。我们的数据支持端粒酶基于端粒和非端粒效应的概念，并为在UC中使用端粒酶抑制剂提供了进一步的理论依据。
