Significance of cyclooxygenase-2 expression in human primary hepatocellular carcinoma

AIM: To clarify the significance of cyclooxygenase-2 (COX-2) expression in human primary hepatocellular carcinoma (HCC) and adjacent nontumorous tissues. METHODS: The COX-2 protein and mRNA were investigated in 27 HCC tissues with adjacent nontumorous tissues, and 5 histologically normal liver tissues,using immunohistochemistry and in situ hybridization. RESULTS: The well-differentiated HCC expressed COX-2 protein (5.68 +/- 1.19) more strongly than moderated HCC (3.43 +/- 1.98) and poor differentiated HCC (3.33 +/- 1.50) (P<0.05 respectively), adjacent nontumorous tissues (4.93 +/- 1.05) and normal liver tissues (3.20 +/- 1.92) (P<0.01 respectively); More intensive staining of COX-2 in adjacent nontumorous tissues was observed than that in normal liver tissues (P<0.05). There was no significant difference among adjacent nontumorous tissues, moderately differentiated HCC and poorly differentiated HCC (P>0.05). The expression of COX-2 mRNA was observed in the cytoplasm of the cells of HCC and of the hepatocytes in adjacent nontumorous tissues in which COX-2 protein was positive. CONCLUSION: The overexpression of COX-2 in well-differentiated HCC suggests that COX-2 may play a role in the early stages of hepatocarcinogensis.