In situ detection of telomerase enzymatic activity in human hepatocellularcarcinogenesis

Telomerase enzymatic activity has been detected in most human malignant tum ours including hepatocellular carcinoma. In order to assess the cellular so urce, the topographic distribution, and the chronology of telomerase re-exp ression during human liver carcinogenesis, an in situ technique derived fro m the standard TRAP (telomeric repeat amplification protocol) assay was set up that allowed the detection of telomerase enzyme activity at the cellula r level on frozen liver tissue sections. In situ TRAP (ISTRAP) was performe d on 27 hepatocellular carcinomas (HCCs) and 57 non-tumour livers, includin g normal liver without HCC, liver samples adjacent to tumour with and witho ut hepatic cirrhosis, and biopsies of chronic hepatitis. In HCC, telomerase was detected in the nuclei of liver tumour cells in 23/27 cases (85%), wit h a heterogeneous distribution within the tumour. This signal was also dete cted in clusters of hepatocytes in 16/26 (61%) samples of liver adjacent to HCC, in 10/23 (43%) cases of chronic viral hepatitis without adjacent HCC, and in scattered nuclei of 2/8 histologically normal livers. Comparison of the results obtained with ISTRAP and standard TRAP assays on tissue extrac ts suggests a gain in sensitivity with the in situ technique. This study co nfirms that telomerase is expressed in most HCCs and suggests that focal te lomerase reactivation is an early event during human liver carcinogenesis. ISTRAP is a sensitive technique that allows the study of telomerase express ion in the morphological context. Copyright (C) 2001 John Wiley & Sons, Ltd .