Telomerase activity in benign and malignant human thyroid nodules

Telomerase is a ribonucleoprotein polymerase which contains an integral RNA and synthesizes TTAGGG nucleotide repeats at the ends of chromosomes in vertebrates. Accumulated evidence has indicated that telomerase is stringently repressed in normal human somatic tissues but reactivated in immortal and cancer cells, suggesting that activation of telomerase may play an important role in carcinogenesis. In order to assess the role of telomerase in the development of thyroid cancer, we measured the telomerase activity in 19 frozen samples obtained from patients with benign and malignant thyroid nodules by employing a recently developed sensitive PCR-based telomerase assay (telomeric repeat amplification protocol: TRAP). Telomerase activity was detected in all the thyroid cancer tissues (9 of 9) and 4 out of 8 benign thyroid nodules showed telomerase activity. Three of thyroid cancers with high telomerase activity had an unfavorable prognosis, whereas six cancers with low telomerase activity were associated with a favorable prognosis. Interestingly, Hashimoto's thyroiditis tissues also showed telomerase activity. These results indicate that telomerase may play a key role during thyroid carcinogenesis.