Telomerase activity in brain tumors.

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Telomerase activity in brain tumors was analyzed. Telomerase activity was examined in surgically resected 41 brain tumors, A172 human glioblastoma cells, and C6 rat glioma cells by means of telomeric repeat amplification protocol (TRAP) assay. In the 41 tumors, the activity of telomerase was compared with histologic diagnosis, the MIB-1 proliferative cell index and patient's prognosis. In A 172 glioblastoma cells and C6 glioma cells, the changes in the telomerase activity of the cells were analyzed during differentiation induced by dibutyryl cyclic AMP, theophylline and retinoic acid. Telomerase activity in rat gliomas induced by ethylnitrosourea administration in pregnant rats was also examined.Twelve of 20 glioblastomas, 2 of 2 oligodendrogliomas and 3 of 3 metastatic brain tumors demonstrated telomerase activity. However, anaplastic astrocytoma, low grade astrocytoma and meningioma exhibited no activity. Although no clear relations were confirmed in glioblastoma between telomerase activity and the MIB-1 proliferative cell index, the telomerase activity tended to correlate with patient's prognosis. After the cell differentiation, the telomerase activities of A 172 glioblastoma cells and C6 glioma cells were strongly decreased. There were no different telomerase activities among growth stages of rat gliomas induced by ethylnitrosourea.These results suggest that telomerase activity may be an important marker of brain tumor malignancy and that functional inhibition of the activity may play a role during differentiation of glioma cells.