Cyclooxygenase-2 expression in equine tumors.
Authors: Thamm D H, Ehrhart E J, Charles J B, Elce Y A
Journal: Veterinary pathology
Summary
# Editorial Summary: COX-2 Expression in Equine Tumours Cyclooxygenase-2 (COX-2) is an enzyme that promotes tumour growth, resists programmed cell death, stimulates blood vessel formation, and suppresses immune responses—making it an attractive therapeutic target in human and canine oncology. Thamm and colleagues examined COX-2 expression across three common equine tumour types using immunohistochemistry on archived tissue samples: 14 sarcoids, 11 melanomas, and 37 squamous-cell carcinomas (SCC) from various body sites. Their findings revealed marked differences in COX-2 prevalence: whilst only 14% of sarcoids expressed the enzyme, 64% of melanomas did so, and crucially, 86% of SCC samples were COX-2-positive—with over half of these showing moderate-to-strong staining intensity. Expression patterns were independent of tumour location, suggesting COX-2 inhibition could represent a broadly applicable adjunctive strategy for equine SCC and melanoma management. For practitioners managing horses with these malignancies, these results support investigation of COX-2-inhibiting drugs (such as firocoxib) as potential therapeutic options, particularly given the poor prognosis typically associated with equine SCC and the limited systemic treatment options currently available.
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Practical Takeaways
- •Squamous cell carcinomas and melanomas in horses frequently express COX-2, making them potential candidates for COX-2 inhibitor treatment as an adjunct or alternative therapy
- •Sarcoids show low COX-2 expression, suggesting COX-2 inhibitors may be less effective for this tumor type
- •COX-2 inhibitor therapy warrants investigation in equine oncology, particularly for SCC cases with moderate-to-strong COX-2 expression
Key Findings
- •COX-2 was expressed in 2 of 14 sarcoids (14%), 7 of 11 melanomas (64%), and 32 of 37 squamous cell carcinomas (86%)
- •56% of COX-2-positive squamous cell carcinomas demonstrated moderate-to-strong immunoreactivity
- •COX-2 expression did not differ significantly between anatomic sites
- •High COX-2 expression in equine SCC and melanomas suggests potential responsiveness to COX-2 inhibitor therapy