Comparison of telomerase and CD44 expression as diagnostic tumor markers in lesions of the thyroid.

The analysis of the tissue expression patterns of both the telomerase enzyme and the adhesion molecule CD44 has highlighted these molecules as potential tumor markers. In this study, the expression of these markers was analyzed in frozen tissue samples of the same human thyroid lesions, and the data were compared to evaluate their application to tumor diagnosis. The study analyzed 12 malignant specimens, including 5 papillary, 3 follicular, 2 anaplastic, 1 medullary, and 1 low-grade Hurthle cell carcinoma and 17 specimens from benign lesions, including cases of adenoma, hyperplasia, and Graves' disease. Telomerase expression was analyzed by assay of enzyme activity using the telomeric repeat amplification protocol and by reverse transcription-PCR detection of human telomerase reverse transcriptase (hTERT) mRNA. Nine of 12 (75%) malignant samples and the two Graves' disease samples were evaluated as positive for telomerase activity by the telomeric repeat amplification protocol assay. The presence of hTERT mRNA was detected in 8 (67%) of 12 malignant tissues and in 5 (29%) of 17 benign thyroid tissue samples. The expression of CD44 transcripts containing variant exons 7, 8, and 11 was evaluated by reverse transcription-PCR/Southern blot analysis. Of the 12 malignant samples, 9 (75%) included transcripts containing exon 7, 10 (83%) included transcripts containing exon 11, and 11 (92%) included transcripts containing exon 8. However, these CD44 exons were also present in transcripts in a high proportion of benign samples. Five (28%), 10 (59%), and 6 (35%) benign samples contained CD44 transcripts, including variant exons 7, 8, and 11, respectively. The measurement of telomerase activity proved to be the most specific for the detection of thyroid carcinoma in frozen tissue samples as a single analyte, but diagnostic accuracy was increased by the combination of telomerase and CD44 analyses.