TELOMERASE ACTIVITY IN HUMAN THYROID CARCINOMAS ORIGINATING FROM THE FOLLICULAR CELLS

Telomerase activity is known to be absent from most normal and well-di fferentiated tissues, although being detectable in the vast majority o f malignant tumors. An increasing number of reports demonstrate that t elomerase may be activated in benign tumors, such as adenomas. We have investigated a series of normal and neoplastic thyroid tissues for th e presence of telomerase activity. As expected, all normal thyroid tis sues (n = 20) had no display of telomerase activity. Amongst cancers, the incidence of telomerase activity varied with the histological subt ypes. Telomerase activity was present in only 3/15 cases (20%) of papi llary carcinomas. Telomerase activity was more frequently detected in follicular (4/6) and in undifferentiated (2/3) carcinomas. Unexpectedl y, one case (1/12) of adenoma contained high levels of telomerase acti vity. Taken together, these results indicate that telomerase may play some role in the pathogenesis of thyroid tumors, in particular in foll icular and undifferentiated carcinomas that are known to have the most aggressive behavior.