Expression of cyclooxygenase-2 in transitional cell carcinoma of the urinary bladder in dogs

Objective—To evaluate expression of cyclooxygenase (COX)-1 and COX-2 in the urinary bladder epithelium of clinically normal dogs and in transitional cell carcinoma cells of dogs. Animals—21 dogs with transitional cell carcinoma of the urinary bladder and 8 dogs with clinically normal urinary bladders. Procedure—COX-1 and COX-2 were evaluated by use of isoform-specific antibodies with standard immunohistochemical methods. Results—COX-1, but not COX-2, was constitutively expressed in normal urinary bladder epithelium; however, COX-2 was expressed in neoplastic epithelium in primary tumors and in metastatic lesions of all 21 dogs and in new proliferating blood vessels in 3 dogs. Also, COX-1 was expressed in the neoplastic cells. Conclusions and Clinical Relevance—Lack of expression of COX-2 in normal bladder epithelium and its substantial expression in transitional cell carcinoma cells suggest that this isoform may be involved in tumor cell growth. Inhibition of COX-2 is a likely mechanism of the antineoplas...