Precancerous hepatic nodules had significant levels of telomerase activitydetermined by sensitive quantitation using a hybridization protection assay

BACKGROUND. Telomeric repeat amplification protocol using internal telomera se assay standard (ITAS) (conventional TRAP) has detected telomerase activi ty in various malignant tumors. With conventional TRAP, it is difficult to differentiate quantitatively low levels of telomerase activity between well -differentiated hepa tocellular carcinomas (HCCs) and dysplastic nodules be cause of quantitative limitation. To apply a telomerase assay for different ial diagnosis, we used a hybridization protection assay combined with TRAP (TRAP/HPA). This combination had better sensitivity and wider linearity tha n conventional TRAP. METHODS. TRAP/HPA was applied for quantitative measurement of telomerase ac tivity in Various hepatic tissues. Telomerase activity was evaluated in 10 precancerous hepatic nodules, 17 well-differentiated HCCs, 19 moderately di fferentiated HCCs, 5 poorly differentiated HCCs, 22 nontumorous chronic hep atic disease samples, and 2 normal liver tissues. RESULTS. Telomerase activity in HCCs tended to increase according to the ma lignant transformation. The average relative telomerase activity in 0.6 mu g protein, which was expressed as cell equivalent activity of MKN-1, a gast ric carcinoma cell line, was 8.5 in precancerous hepatic nodules, 87 in wel l-differentiated HCCs, 265 in moderately differentiated HCCs, 447 in poorly differentiated HCCs, and 0.4 in nontumorous hepatic tissues, including chr onic liver diseases. CONCLUSIONS. TRAP/HPA was sensitive enough to distinguish the telomerase ac tivity in precancerous hepatic nodules from that in other lesions. Telomera se activity in precancerous hepatic nodules was higher than that in nontumo rous hepatic tissues. However, the activity in precancerous hepatic nodules was lower than that in well-differentiated HCCs, although statistically no t significant. The authors suggest that precancerous hepatic nodules with t elomerase activity above the diagnostic cutoff level (twice the highest act ivity in nontumorous hepatic tissues, or the 2 cell equivalent activity of MKN-1) should be treated as malignancy. (C) 2000 American Cancer Society.