In situ detection of telomerase catalytic subunit mRNA in glioblastoma multiforme

Activation of telomerase may allow unlimited cell proliferation and immorta lization, One of the telomerase protein subunits has a reverse transcriptas e (hTERT) activity that is essential for telomerase Function and regulation . In human gliomas, telomerase is frequently associated with malignant tumo r progression. In our study, we investigated the expression of hTERT at the cellular level in 34 primary de novo glioblastoma multiforme (GBM) by in s itu hybridization (ISH). The expression oh hTERT; in tumor tissue was also assessed by Ri-PCR, In addition, telomerase activity measured by telomeric repeat amplification protocol (TRAP) and telomere length polymorphism assay ed by telomere restriction fragment (TRF) Southern blot were investigated. We found that all GEM, including those with negative TRAP reaction, contain ed abundant amounts of cytoplasmic hTERT mRNA, interestingly, the ISH analy sis revealed that the hTERT mRNA was homogeneously expressed by the whole t umor cell population in about 60% of the GBM. In the remaining cases. hTERT was absent in subsets of tumor cells. TRF analysis, which shows that both TRAP-positive and TRAP-negative de novo GBM have elongated telomeres, furth er supports that telomerase activity is present in all de novo GEM. Correla tions with tumor size and extent of necrosis suggest that hTERT reactivatio n is an early event in GEM development and that telomerase activity may be lost in subpopulations of neoplastic cells during tumor progression. Finall y, ISH analysis of hTERT mRNA seems to provide a prognostic parameter for p rimary de novo GEM. int, J. Cancer 88:895-901, 2000. (C) 2000 Wiley-Liss, I nc.