Cyclooxygenase-2 in human malignant fibrous histiocytoma: correlations with intratumoral microvessel density, expression of vascular endothelial growth factor and thymidine phosphorylase

Cyclooxygenase-2 (COX-2) has been found to be up-regulated in several types of human malignant tumors and proposed to have a role in the angiogenic process. This study examined the expression of COX-2 in two human malignant fibrous histiocytoma (MFH) cell lines by Western blotting, which showed a specific single band at 72 kDa. Immunohistochemistry was conducted in 35 MFHs and 30 benign fibrohistiocytic tumors (BFHTs), comparing the expression of vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP), as well as intratumoral microvessel density (IMVD). COX-2 expression was noted in 22 (62.9%) MFHs, but in no BFHT. IMVD values were significantly higher in the MFHs (90.6+/-8.0) than BFHTs (27.9+/-3.1), and also in the COX-2 positive (104.5+/-11.3) than negative (67.2+/-5.8) MFHs. VEGF and TP expression was also associated with a significantly higher level of COX-2, as well as greater IMVD. The highest IMVD values were noted in the 17 MFHs (120.8+/-11.5) expressing all three factors. Clinical analysis demonstrated poorer survival in the 18 COX-2 positive MFHs than in the 10 negative ones, although the small number of cases did not reveal a significant difference. The results overall indicated that COX-2 expression is associated with intratumoral angiogenesis, which might provide favorable conditions for tumor progression in human MFHs.