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.
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