Assessment of cyclooxygenase-1 and 2 gene expression levels in chronic autoimmune thyroiditis, papillary thyroid carcinoma and nontoxic nodular goitre.

INTRODUCTION: The cyclooxygenases are a group of enzymes catalyzing the formation of prostaglandins from arachidonic acid. Cyclooxygenase-1 (COX-1) is a constitutive form, thought to be a "housekeeping gene", with constant levels of expression in most tissues. COX-1 expression in the thyroid gland, except for medullary thyroid carcinoma, has not been a subject of much interest. Cyclooxygenase-2 (COX-2) can be expressed in response to various stimuli, such as mitogens, hormones, cytokines, growth factors. The product of COX-2 activity has been implicated in carcinogenesis. Recent studies have shown that up-regulation of COX-2 is associated with numerous neoplasms. Hereby, we present a study analysing COX-1 and COX-2 expression in papillary thyroid carcinoma (PTC), Hashimoto thyroiditis (HT) and nontoxic nodular goitre (NNG) in fine needle aspiration biopsy (FNAB) washouts and in postoperative tissue. MATERIAL AND METHODS: Cytological specimens from 120 patients (105 females and 15 males) have been studied, including patients with HT, PTC and NNG. Moreover, we have examined postoperative tissue specimens from 51 patients with PTC and NNG. The methods of molecular analysis have included extraction of total RNA from FNAB cytological material and postoperative tissues, spectrophotometric assessment of the RNA purity, cDNA synthesis in reverse transcription reaction and an analysis of genes expression data by real-time PCR. RESULTS: The performed analysis has revealed statistically significant higher expression level of the COX-2 gene in PTC group, in comparison with HT and NNG groups (in both cytological and postoperative material). In PTC patients, COX-2 gene expression levels in the material obtained by FNAB were similar to those in the postoperative thyroid tissue. No correlations between COX-2 gene expression level and TNM staging in PTC samples have been observed. There were no correlations between COX-2 expression and anti-TPO antibodies level, or patient's sex or age in the studied groups. Also, there were no correlations of COX-1 gene expression level among PTC, HT and NNG groups. CONCLUSIONS: Our results suggest that COX-2 gene does not participate in the mechanisms involved in molecular association of HT with PTC. However, in case of PTC itself, it may play some role in neoplastic transformation.