Differentiating alternative splice variant patterns of human telomerase reverse transcriptase in thyroid neoplasms.
BACKGROUND
Although fine-needle aspiration (FNA) biopsy of thyroid nodules is very sensitive in detecting thyroid malignancy, it remains ambiguous in 20-30% of cases. Current biomarkers for thyroid cancer lack either the sensitivity or specificity to substantially address this clinical problem. The aim of this study was to investigate the gene expression patterns of human telomerase reverse transcriptase (hTERT) alternative splice variants in benign and malignant thyroid tumors in an attempt to find a more reliable biomarker in the differential diagnosis of thyroid nodules.


METHODS
One hundred and thirty-three thyroid tumors from eight histopathological tumor types were collected from patients undergoing thyroid surgery at Johns Hopkins Hospital. Gene expression patterns of hTERT alternative splice variants were investigated in the tumors by nested reverse transcriptase-PCR. Telomerase enzyme activity was evaluated in a subset of 16 samples associated with the different hTERT patterns. Association of c-myc expression and hTERT patterns was also examined.


RESULTS
Malignant thyroid tumors exhibited a greater proportion of the active full-length hTERT transcript (0.57 +/- 0.15) than inactive splice variants, alpha(-) (0.13 +/- 0.02), or beta(-)/alpha(-)beta(-) deletion transcripts (0.30 +/- 0.11; p < 0.001). The opposite was observed in benign tumors, which exhibited greater proportions of beta(-)/alpha(-)beta(-) deletion transcripts (0.64 +/- 0.08) than either the full-length (0.19 +/- 0.06) or alpha(-) deletion transcripts (0.17 +/- 0.02; p < 0.001). Similar results were observed among a diagnostically challenging subset of 50 thyroid tumors that were suspicious for malignancy on FNA. Further, increased telomerase enzymatic activity was only associated with expression of the full-length hTERT isoform. In contrast, c-myc expression, which has been implicated in hTERT regulation, correlated with overall hTERT transcription without specificity for expression of the full-length isoform.


CONCLUSIONS
These differences in gene expression patterns of hTERT alternative splice variants may provide a useful adjunct to FNA diagnosis of suspicious thyroid tumors.
Wang
Yongchun
Y
Department of Surgery, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21287, USA.
Kowalski
Jeanne
J
Tsai
Hua-Ling
HL
Marik
Radharani
R
Prasad
Nijaguna
N
Somervell
Helina
H
Lo
Pang-Kuo
PK
Sangenario
Lauren E
LE
Dyrskjot
Lars
L
Orntoft
Torben F
TF
Westra
William H
WH
Meeker
Alan K
AK
Eshleman
James R
JR
Umbricht
Christopher B
CB
Zeiger
Martha A
MA
D000236:Adenoma / Q000235:genetics; D018249:Adenoma, Oxyphilic / Q000235:genetics; D017398:Alternative Splicing; D018265:Carcinoma, Papillary, Follicular / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000096:biosynthesis; D012372:ROC Curve; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019098:Telomerase / Q000096:biosynthesis / Q000235:genetics*; D013964:Thyroid Neoplasms / Q000235:genetics*
D016271:Proto-Oncogene Proteins c-myc; D019098:Telomerase