Abstract 3215: Expression of hTERT predicts immortalization of glioma-derived primary cell cultures and is associated with shorter overall survival in glioblastoma patients

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Abstract hTERT represents the catalytic subunit of telomerase leading to cell immortalization by stabilizing telomere lengths. Aim of this study was to characterise hTERT expression in gliomas and the derived cell cultures with a focus on glioblastomas (GBM) and to investigate its relation with tumor cell immortalization in vitro and disease progression in vivo. During the last nine years primary cell cultures were established from 265 tumor tissues obtained during surgery and histologically verified according to WHO criteria as low grade glioma WHO I/II (n=22) and anaplastic astrocytoma WHO III (n=15), GBM WHO IV (n=219), gliosarcoma (n=7) and giant cell glioblastoma (n=2). hTERT gene expression was investigated in all primary cell cultures and additionally in GBM tumor tissues (n=80) by RT-PCR. hTERT mRNA expression levels were calculated relatively to GAPDH mRNA amplified concomitantly and in subgroups verified by real-time RT-PCR. Telomerase enzyme activity was confirmed using the Telomeric Repeat Amplification Protocol (TRAP) of the TRAPeze Telomerase Detection Kit (Chemicon). hTERT expression data were compared to overall survival of GBM patients. Thirty-one percent (81/265) of the analysed cell cultures displayed hTERT gene expression. All of the hTERT-expressing primocultures, which were exclusively high grade gliomas (WHO III/ IV), developed into stable, immortal cell lines whereas hTERT negative cells failed to grow in vitro or ceased growth between passages 1 to 10. In contrast, all low grade gliomas (WHO I/II; n=22) were negative with respect to hTERT expression and characterised by limited in vitro cultivation demonstrating the less aggressive potential of these tumors. In parallel in vivo hTERT expression was analysed in 80 GBM tumor samples. 37/80 (46%) showed detectable hTERT expression and 54% (43/80) were negative with respect to hTERT. Kaplan-Meier survival estimates revealed a significant survival benefit for patients whose tumors lacked hTERT expression (p< 0.04) with a median survival of 20.1 months versus 14.3 months for patients whose tumors expressed hTERT. Summing up our data show that a) telomerase activity, reflected by hTERT expression is essential for successful in vitro growth of brain glioma-derived primocultures/cell lines. Thus in vitro studies on GBM generally focus exclusively on the hTERT-positive patient subgroup. b) hTERT gene expression can predict the potential to establish a stable, immortal cell model from a brain tumor specimen. Focussing on hTERT expression in vivo our data revealed that hTERT expression is associated with significantly shorter overall survival in GBM patients. Thus hTERT might have quality as prognostic biomarker predicting tumor aggressiveness. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3215.