Expression of cyclooxygenase-2 in gastric cancer and its relation to liver metastasis and long-term prognosis

AIM： To investigate the expression of cyclooxygenase-2 （COX-2） in gastric cancer and its relation with the liver metastasis and prognosis. METHODS： Expression of COX-2 mRNA and protein was examined in gastric cancer and its paired substantial normal tissue by semi-quantitative reverse transcription- polymerase chain reaction and immunohistochemistry. The relation between COX-2 expression and prognosis was investigated in 195 cases. RESULTS： The expression of COX-2 mRNA in gastric cancer tissue was significantly higher than that in normal tissue in 47 cases （w = 792, P〈0.01）. The COX-2 mRNA in pT3-4 tissue expressed higher than that in pT1-2 tissue （w = 204, P〈0.05）. The positive expression rate of COX-2 protein was 57.9% （113/195）. The COX-2 expression was significantly related to histological type, lymphnode metastasis, venous invasion and liver metastasis （P〈0.05）. No relation was found between COX-2 expression and invasion depth, peritoneal metastasis and International Union against Cancer TNM stage. The multiple regression analysis showed that the COX-2 expression and venous invasion were obviously associated with liver metastasis （P〈0.05）. However, there was no significant correlation between COX-2 immunoreactivity and prognosis. CONCLUSION： COX-2 may play an important role in the development of gastric cancer, and the over-expression of COX-2 protein may be a high risk factor for liver metastasis.