Cohort study of COX-1 and COX-2 expression in canine rectal and bladder tumours.
OBJECTIVE
To determine the role that cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) play in malignant transformation in canine transitional cell carcinoma and rectal tumours.


METHODS
Histological sections of 21 canine rectal adenocarcinomas and 18 canine transitional cell carcinomas were stained for COX-1 and COX-2. Mann-Whitney non-parametric tests were applied to determine if there was any relationship between the percentage of cells expressing COX-1 or COX-2, and between COX-1 and COX-2 staining intensity and age, breed or sex.


RESULTS
For rectal adenocarcinomas, 19.0 per cent of the sections were negative for COX-1 and COX-2. A further 38.1 per cent of the sections were negative for COX-2 but positive for COX-1, and 38.1 per cent of the sections had rare or occasional single cells positive for COX-2. No significant differences were found in COX staining when compared with age, breed or sex. For transitional cell carcinomas, all of the sections were positive for COX-1 and COX-2. For COX-2 staining, 16.7 per cent had more than 30 per cent positive cells. For COX-1 staining, 38.9 per cent had more than 30 per cent positive cells. There was a significant increase in the percentage of COX-1 positive cells in small breed dogs (P = 0.0337).


CONCLUSIONS
The variations in COX expression reported in this study may explain the differences in the clinical response of transitional cell carcinomas and rectal adenocarcinomas following treatment with non-steroidal anti-inflammatory drugs.
Knottenbelt
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C
Department of Veterinary Clinical Studies, Institute of Comparative Medicine, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow G61 1QH.
Mellor
D
D
Nixon
C
C
Thompson
H
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Argyle
D J
DJ
D000230:Adenocarcinoma / Q000201:enzymology / Q000235:genetics / Q000662:veterinary*; D000367:Age Factors; D000818:Animals; D002295:Carcinoma, Transitional Cell / Q000201:enzymology / Q000235:genetics / Q000662:veterinary*; D002471:Cell Transformation, Neoplastic; D015331:Cohort Studies; D051545:Cyclooxygenase 1 / Q000235:genetics / Q000378:metabolism; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D004283:Dog Diseases / Q000201:enzymology* / Q000235:genetics; D004285:Dogs; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D007150:Immunohistochemistry; D008297:Male; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics* / Q000378:metabolism; D012004:Rectal Neoplasms / Q000201:enzymology / Q000235:genetics / Q000662:veterinary*; D001749:Urinary Bladder Neoplasms / Q000201:enzymology / Q000235:genetics / Q000662:veterinary*
D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases