In situ detection of hTERT mRNA relates to Ki-67 labeling index in papillary thyroid carcinoma

Background. Telomerase is activated in most human cancers but is inactivate in adult somatic tissues except for some proliferating cell lineages. The maintenance of telomerase activity may be a critical step of cellular immortalization and transformation. Materials and methods. We analyzed the expression of human telomerase reverse transcriptase (hTERT) using in situ hybridization and compared it to Ki-67 immunoreactivity in 29 cases of papillary thyroid carcinoma (PTC) and 17 cases of benign thyroid disease. Results. The hTERT messenger RNA (mRNA) was expressed in the cytoplasm of carcinoma cells with moderate (n = 10) to strong intensity (n = 10) in 69% (20 of 29) PTC cases. Human TERT was found in only 29% (5 of 17) cases of benign thyroid disease. Human TERT gene expression was preferentially detected in PTC (P = 0.021). The Ki-67 labeling index was observed in 16 cases of PTC (16 of 29; 55.2%). This result was significantly different from that of benign thyroid disease (P = 0.014). The Ki-67 labeling index related to the intensity of hTERT mRNA expression (r = 0.51; P = 0.005) and was inversely associated with the follicular variant of PTC (r = -0.413; P = 0.026). No statistically significant difference was found between hTERT expression and histological subtype of PTC. Conclusions. Our results demonstrated that expression of hTERT could be detected using in situ hybridization in PTCs and was significantly distinguishable from that of benign thyroid disease. Human TERT expression was related to the Ki-67 labeling index, indicating that coupling of telomerase activation with cell proliferation was the associated mechanism for tumorigenesis. (C) 2001 Academic Press.