High prevalence of cyclooxygenase 2 expression in papillary thyroid carcinoma.
BACKGROUND
Cyclooxygenase-2 (COX-2) seems to play a role in the development and carcinogenesis of papillary thyroid carcinoma. Its incidence of expression and potential application as a tumor marker remain to be elucidated.


METHODS
Immunohistochemical staining for COX-2 expression was performed for 30 papillary thyroid carcinoma (PTC) and 40 benign thyroid specimens. COX-2 mRNA expression was analyzed using a reverse transcriptase-polymerase chain reaction (RT-PCR) for paired fresh frozen tissues removed from surgically resected PTC specimens.


RESULTS
COX-2 expression was detected by immunohistochemistry in 27 of 30 (90%) PTC but was absent in 40 benign thyroid specimens, including 27 nodular hyperplasia, 7 follicular adenoma and 6 lymphocytic thyroiditis. Two of the three COX-2 negative carcinomas were follicular variant of PTC. RT-PCR analysis confirmed COX-2 mRNA over-expression in 14 of 20 (70%) paired specimens of PTC. Real-time quantitative RT-PCR showed that the level of COX-2 mRNA expression was significantly higher in PTC than in both the adjacent non-cancerous tissues and the benign thyroid specimens.


CONCLUSIONS
COX-2 is frequently expressed in PTC but not in benign thyroid specimens. COX-2 expression may serve as a useful molecular marker for PTC in cases of diagnostic difficulty.
Lo
Chung-Yau
CY
Department of Surgery, University of Hong Kong Medical Centre, Queen Mary Hospital, China. cylo@hku.hk
Lam
Kin-Yin
KY
Leung
Pauline P
PP
Luk
John M
JM
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000201:enzymology*; D051546:Cyclooxygenase 2; D005260:Female; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins; D008875:Middle Aged; D011451:Prostaglandin-Endoperoxide Synthases / Q000032:analysis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013961:Thyroid Gland / Q000201:enzymology; D013964:Thyroid Neoplasms / Q000201:enzymology*
D008565:Membrane Proteins; D012333:RNA, Messenger; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases