Cyclooxygenase-2 Expression is Associated with Histologic Tumor Type in Canine Mammary Carcinoma

• Published in: Veterinary pathology 2005-11, Vol.42 (6), p.776-780
• Main Authors: Heller, D. A, Clifford, C. A, Goldschmidt, M. H, Holt, D. E, Shofer, F. S, Smith, A, Sorenmo, K. U
• Format: Article
• Language: English
• Subjects: adenocarcinoma; Adenocarcinoma - enzymology; Adenocarcinoma - veterinary; Animals; Carcinoma - enzymology; Carcinoma - veterinary; Cyclooxygenase 2 - metabolism; Dog Diseases - enzymology; Dogs; enzyme inhibitors; Female; gene expression; Gene Expression Regulation, Neoplastic; Immunohistochemistry - veterinary; mammary neoplasms (animal); Mammary Neoplasms, Animal - enzymology; prostaglandin synthase
• ISSN: 0300-9858; 1544-2217
• DOI: 10.1354/vp.42-6-776

Cyclooxygenase-2 (COX-2) is an inducible member of the family of cyclooxygenase enzymes that has been implicated in the genesis of numerous cancers. The role of COX-2 in canine mammary neoplasia remains to be more clearly elucidated. The goal of the study reported here was to determine whether a direct association between levels of COX-2 expression and tumor histologic subtype exists in canine mammary carcinoma. Immunohistochemical analysis was performed using a polyclonal antiprostaglandin G/H synthase 2 IgG COX-2 antibody. Sections from the kidneys of young dogs, which stain positive for COX-2 in the macula densa, served as positive controls. Slides were reviewed by a single pathologist, and were evaluated for COX-2 expression according to previously established scales. Positive-staining tumors were given a COX-2 staining distribution (on the basis of the percentage of positive staining cells in five 400x fields) and intensity score according to previously established scales. The product of the COX-2 staining distribution and intensity scores was calculated to create a COX-2 staining index. COX-2 expression was detected in 28 of 50 (56%) samples evaluated. Anaplastic carcinomas had a significantly higher COX-2 staining distribution, intensity, and index, compared with those for adenocarcinomas (P < 0.0001). The overall percentage of positive tumors (56%) was consistent with that of prior studies. To the authors' knowledge, these results indicate, for the first time, a direct association between COX-2 expression and tumor histologic subtype in canine mammary carcinomas. Future research directed at measuring tumor response in canine mammary carcinoma patients treated with a selective COX-2 inhibitor is indicated.