High COX-2 expression is associated with increased angiogenesis, proliferation and tumoural inflammatory infiltrate in canine malignant mammary tumours: a multivariate survival study.

COX-2 expression affects mammary tumourigenesis by promoting angiogenesis and cell proliferation, encouraging metastatic spread and tumour-associated inflammation. Samples of canine mammary tumours (n = 109) were submitted to immunohistochemistry to detect COX-2, CD31, VEGF, Ki-67, CD3 and MAC387 expression. Concurrent high expression of COX-2/CD31, COX-2/VEGF, COX-2/Ki-67, COX-2/CD3 and COX-2/MAC was associated with elevated grade of malignancy, presence of intravascular emboli and presence of lymph node metastasis. Tumours with high COX-2 (P < 0.001) and tumours with concurrent expression of high COX-2 and high CD31 (P = 0.008); high VEGF (P < 0.001); high Ki-67 (P < 0.001); high CD3+ T-lymphocytes (P = 0.002) and elevated MAC387 macrophages (P = 0.024) were associated with shorter overall survival (OS) time. Interestingly the groups with high COX-2/CD31 and high COX-2/VEGF retained their significance after multivariate analysis arising as independent predictors of OS. Present data highlight the importance of COX-2 in canine mammary tumourigenesis.