Regional telomerase expression in oligodendrogliomas

Telomerase is a novel ribonucleoprotein enzyme which is expressed in the majority of solid human tumors and downregulated in non-neoplastic adult somatic tissues. Expression of telomerase may be one important mechanism by which neoplastic cells attain immortality. The highest grade primary glial neoplasms, the glioblastoma multiforme, are positive in 1/2 to 2/3 of cases while 19 of 19 oligodendrogliomas. a less malignant glial neoplasm, were reportedly positive for telomerase (Lancet 346:1267-1268, 1995; Am. I. Clin. Pathol, in press). In this study, we examined four to seven regions from each of four oligodendrogliomas and seven GBMs to test whether telomerase expression was uniform across different regions of these tumors. Tumor tissue was snap-frozen at the time of surgery and analyzed for telomerase expression using the TRAP assay (Science 266:12011-2015, 1994). Matching mirror image tissue sections were utilized to assess tissue adequacy and histological features. Oligodendrogliomas were uniformly positive or negative for telomerase expression across multiple regions of tumor, whereas GBMs showed regional heterogeneity by TRAP assay for telomerase expression. One primary moderately anaplastic oligodendroglioma demonstrated 6 of 6 regions positive for telomerase while a recurrent anaplastic oligoastrocytoma demonstrated 4 of 4 regions negative. A primary, grade 2 oligodendroglioma showed 5 of 5 regions negative. In contrast, only 1 of 7 GBMs thus far tested showed uniform telomerase expression in all 5 to 7 regions tested. This preliminary result suggests that further study is warranted regarding the homogeneity vs heterogeneity of telomerase expression in oligodendrogliomas vs GBMs.