Abstract: Objective To investigate the expression of cyclooxygenase-2 (COX-2) in malignant melanoma.Methods The expression of COX-2 was determined by immunohistochemistry in 45 cases of malignant melanoma and 25 intradermal nevi.The correlation between the immunohistochemistry findings and clinical data (including age,gender,TNM staging,and presence of lymph node metastases) was also analyzed.The COX-2 expression in three human melanoma cell lines (A375,CRL-1585,and Libr) and cultured human melanocytes was assessed by Western blot.Results Thirty six of the 45 malignant melanoma samples and none of the 25 intradermal nevi were positive for COX-2.The positivity rates of COX-2 in lymph node metastasis group and in advanced stage (TNM stagesⅢandⅣ) were significant higher than those in lymph node negative group and in early stage (TNM stagesⅠandⅡ)(92.3% versus 63.2%,89.7% versus 62.5%,respectively;P<0.05).The expression of COX-2 was significantly associated with the ectopic expression of β-catenin (r=0.45).Western blot analysis confirmed negative COX-2 expression in normal human melanocytes and Libr melanoma cell line,whereas the expression of COX-2 was markedly elevated in A375 and CRL-1585 melanoma cells.Conclusions The results indicate that COX-2 is overexpressed in human malignant melanoma and melanocytes,and may be involved in the development and progress of melanoma.

Key words: Melanoma, Prostaglandin-endoperoxide synthase, Beta-catenin