Cyclooxygenase-2 is Involved in the Progression of Thyroid Cancer

Although the inducible form of cyclooxygenase (COX), COX-2, is highly expressed in various cancers and it is also involved in cancer progression, its role in thyroid cancer is not fully understood. We assessed in the situ cyclooxygenase expression in normal thyroids (n=6), Graves' thyroids (n=6), thyroid adenomas (n=12), thyroid follicular (n=15) and papillary carcinomas (n=30). In comparison to the constitutive expression of COX-1, COX-2 was highly expressed in thyroid cancers (90.0% of thyroid papillary carcinomas and 73.3% of thyroid follicular carcinomas) and moderately in thyroid adenomas (25.5%), but barely expressed in normal and Graves' thyroid tissues. This quantitative assessment employed immunohistochemical methods. Thereafter we compared the effect of COX-2 inhibition on a human follicular thyroid carcinoma cell line (WRO), and a human papillary carcinoma cell line (NPA), using selective COX-2 inhibitor(NS-398). The treatment with 50 μM NS-398 suppressed the growth of the COX-2 expressing cells, NPA cells (37.7%;p<0.01) and WRO cells (10.1%;p