COX-1 and COX-2 expression in canine cutaneous, oral and ocular melanocytic tumours

In order to evaluate the potential value of non-steroidal anti-inflammatory drugs (NSAIDs) in the treatment of canine malignant melanoma, expression of cyclooxygenase (COX)-1 and COX-2 was determined in 20 cutaneous, nine oral and two ocular malignant melanomas, and in nine cutaneous melanocytomas. Almost all tumours expressed COX-1, but COX-2 expression was restricted to the malignant tumours being found in 11 of the 20 cutaneous malignant melanomas, all oral malignant melanomas and in one of two ocular malignant melanomas. COX-1 expression did not differ significantly between benign and malignant skin lesions, but COX-2 expression was significantly greater in cutaneous malignant melanoma compared with melanocytoma (P=0.047). COX-2 labelling was particularly intense in the more highly malignant oral tumours. The results of the study suggest that NSAIDs, particularly COX-2 inhibitors, may be useful in the treatment of canine malignant melanoma.