Expression of cyclo-oxygenases-1 and -2, and microsomal prostaglandin E synthase-1 in penile and preputial papillomas and squamous cell carcinomas in the horse.

This study examines the expression of specific enzymes in horse penile and preputial papillomas and carcinomas, and determines that these enzymes may have little value for prevention or treatment, but holds potential for further research in cancer treatment strategies.

Research Background and Objectives

• The research focuses on papillomas and squamous cell carcinoma (SCC), both common diagnoses in horses.
• The potential for papillomas to turn into more dangerous SCCs has sparked interest in understanding the pathogenic mechanisms behind this progression, in hopes of finding preventive measures and treatment targets.
• For this goal, the study focuses on determining the expression (how large a role the enzyme plays) of cyclo-oxygenase 1 (COX-1), cyclo-oxygenase 2 (COX-2), and microsomal prostaglandin E synthase-1 (mPGES-1) in normal tissue, papillomas, and SCCs in horses.
• The researchers also aim to understand if inflammation and tumor differentiation grades influence the expression of these enzymes.

Methods and Results

• Using formalin-fixed paraffin embedded samples from 68 horses, the researchers examined tumor differentiation grade, inflammation degree, and the expression of the aforementioned enzymes by histopathology and immunohistochemistry.
• Inflammation was more pronounced in SCCs compared to papillomas, but it did not appear correlated with the expression of COX-1 or COX-2.
• mPGES-1 expression was weakly correlated with inflammation.
• Expression of COX-1, COX-2, and mPGES-1 were found in a significant portion of lesions. However, very few cells were immunopositive (indicative of the enzymes’ presence) for COX-1 and COX-2.
• COX-1 expression was moderately negatively correlated with tumor differentiation; that is, the lesser the expression of COX-1, the more differentiated the tumor was. Conversely, there was no correlation between COX-2 expression and tumor differentiation. mPGES-1 expression showed a weak negative correlation with tumor differentiation.

Conclusions and Future Implications

• The study concluded that there is poor expression of COX-1 and COX-2 in the horse penile and preputial SCCs, indicating these enzymes may not be of much value as treatment targets.
• mPGES-1 was found to be more prominently expressed in well-differentiated tissue than in poorly-differentiated tissue, suggesting further research into the enzyme’s role in carcinogenesis could be valuable.
• The findings contribute to the existing knowledge of the arachidonic pathway enzyme expression and may advance the development of preventive and therapeutic strategies for equine penile and preputial carcinogenesis.