Expression of COX-2 is increased with age in papillary thyroid cancer.

ABSTRACT

AIMS: To study cyclooxygenase-2 (COX-2) and matrix metalloproteinase-2 (MMP-2) expression in papillary thyroid cancer (PTC). Expression of COX-2 is elevated in various human tumours and it has an important role in carcinogenesis. MMP-2 is also an important component of the metastatic potential of tumours. In PTC the most important factor affecting survival is age, but it is poorly understood why older PTC patients have a worse prognosis. METHODS AND RESULTS: This retrospective study comprised 108 patients with PTC, and we compared patients who were either younger than 35 (n = 59) or older than 55 (n = 49). Paraffin-embedded tumour samples were analysed for COX-2 and MMP-2 protein expression using immunohistochemistry. High (scores 2-3) COX-2 immunostaining was observed in 38/108 (35%) of the tumours, and COX-2 expression was significantly (P = 0.002) higher in the older age group (25/49; 51%) than in the young one (13/59; 22%). CONCLUSIONS: Our study shows that COX-2 expression increases with age. It is possible that the age-related increase in COX-2 expression could explain the more aggressive behaviour of PTC in the older age group compared with the young one.