EXPRESSION OF TELOMERASE RNA COMPONENT CORRELATES WITH THE MIB-1 PROLIFERATION INDEX IN EPENDYMOMAS

Although there is general agreement that certain morphologic subtypes of ependymoma are benign, the biologic behavior of other ependymal neo plasms is poorly understood and not clearly related to conventional hi stopathologic criteria. The absence of universally accepted standards has prompted the search for more objective biologic markers. Telomeras e is an RNA-containing enzyme associated with immortality in prolifera ting stem cells and many tumors. We investigated the proliferative act ivity of 26 ependymomas as determined by MTB-1 immunolabeling and comp ared the results with the in situ expression of human telomerase RNA ( hTR) and WHO tumor grade. The study included 9 WHO grade I ependymomas (6 subependymomas and 3 myxopapillary ependymomas), 13 WHO grade II e pendymomas, and 4 anaplastic (WHO grade III) ependymomas. The prolifer ation index (PI) and telomerase RNA expression were significantly incr eased in grade III ependymomas (p < 0.0001 for PI and p = 0.0015 for h TR). In these tumors, the PI and hTR expression were highly correlated (p = 0.0001). Of note, a single case designated grade II showed both increased proliferative activity and the highest hTR expression detect ed in this series of ependymal neoplasms. Our results suggest that the PI and hTR expression may be important biologic markers, independent of other histopathologic criteria of tumor grade. Future studies exami ning the correlation of MIB-1 cell kinetics and hTR expression with cl inical parameters in selected ependymoma subtypes are needed to determ ine the prognostic relevance of these markers.