Expression of thymidine phosphorylase and cyclooxygenase-2 in melanoma

Abstract

Several studies have reported an increase in vascular structures in malignant melanoma. Neovascularization can be enhanced by several factors. Among them, thymidine phosphorylase (TP) and cyclooxygenase-2 (COX-2) have been reported to play a role. The expressions of TP and COX-2 were evaluated trough immunohistochemistry in a series of 78 primary cutaneous melanomas diagnosed between 2000 and 2004. The expressions of TP and COX-2 through mRNA and western blot analysis were also evaluated in several melanoma cell lines. TP expression and COX-2 expression were considered positive in 25 cases (32%) and 22 cases (28.2%), respectively. TP-positive melanomas showed a lower mitotic rate (P=0.008), smaller thickness (P=0.01), and absence of lymphovascular invasion (P=0.04). COX-2-positive melanomas showed a higher mitotic rate (P=0.01) and higher thickness (P=0.03). COX-2 expression was associated with reduced disease-free survival (P=0.01). COX-2-positive cases showed a trend toward reduced survival, whereas TP was not correlated with overall survival. COX-2 expression was detected in four of 11 melanoma cell lines both by mRNA and by western blot analysis. Our data show that TP expression is associated with more favorable prognostic factors (such as thin melanoma, low mitotic count, and absence of lymphovascular invasion), whereas COX-2 expression is associated with poor prognostic factors (thicker melanoma and high mitotic count).