Telomere length and telomerase catalytic subunit expression in non-astrocytic gliomas

Telomerase activation has been implicated as a major factor in the development of cancer. In our previous study we reported on the telomerase activity of a variety of gliomas. To further investigate the role of telomere and telomerase regulation in the pathogenesis of nonastrocytic gliomas, we examined the telomere length and the mRNA expression of telomerase reverse transcriptase gene (hTERT) and telomerase-associated protein (hTEP) in a series of 27 oligodendroglial and 18 ependymal tumors in this study. No statistical difference was found between the mean telomere length in telomerase-positive and telomerase-negative tumors (11.5 kb vs 13.1 kb; p = 0.424), although a slightly shorter length was observed in telomerase-positive oligodendroglial tumors. mRNA expression of hTERT was highly correlated with the telomerase activity status. hTERT was expressed in 8/8 (100%) and 2/2 (100%) telomerase-positive oligodendroglial and ependymal tumors, respectively, whereas 3/6 (50%) telomerase-negative oligodendroglial tumors and no telomerase-negative ependymal tumors showed expression. In contrast, hTEP1 mRNA was widely expressed in both telomerase-positive and telomerase-negative oligodendroglial and ependymal tumors. Our data support the notion that hTERT plays a critical role in determining the enzymatic activity of human telomerase. It has recently been proposed that both p16(INK4a)/Rb pathway inactivation and telomerase activity were required for immortalization of epithelial cells. Although lack of p16(INK4a) expression was detected in a substantial proportion of tumors, no correlation between the p16(INK4a) or pRb protein expression and telomerase activity was observed in our series of non-astrocytic tumors.