Cyclooxygenase-2 Immunoreactivity in Equine Ocular Squamous-Cell Carcinoma

Abstract

Abstract. Squamous-cell carcinoma (SCC) is the second most common tumor in horses, and 40%-50% may occur in ocular and adnexal structures. Cyclooxygenase (COX)-2 is an inducible enzyme responsible for the production of prostaglandins that control cell growth and the development and progression of cancer. Mechanisms responsible for the initial upregulation of COX-2 in neoplasia are unclear; prolonged sunlight exposure and mutations in the p53 gene may be possibilities. Because the etiopathogenesis of ocular SCC in horses may involve ultraviolet sunlight and p53 mutations, the purpose of this study was to characterize the immunoreactivity of COX-2 in these tumors. Cyclooxygenase-2 expression was found in 6 of 22 (27%) paraffin-embedded equine SCCs. Cyclooxygenase-2 immunoreactivity was associated with the mitotic index (P , 0.001). Strategies to inhibit COX-2 by the use of topical or systemic COX-2 inhibitors might prove to be a safe and economical treatment in some horses with SCC.

Cyclooxygenase-2 Expression in Animal Cancers

“…Another group reported that a small percentage (<10%) of neoplastic cells from 27% of corneal SCCs were only weakly positive. 95 In agreement with this observation, Smith et al 110 recently reported that less than 1% of the neoplastic cells from SCCs originating from the corneoscleral limbus, the third eyelid, and the eyelids were positive for COX-2. Finally, a study reported that the majority (32/37) of SCCs (eye/periocular, prepuce/penis, vulva) were positive for COX-2, with 56% of them having moderate to strong staining, but there was no mention of the localization in the eye and the number of ocular tumors that were positive.…”

Primary Corneal Squamous Cell Carcinoma in a Dog: Clinical and Histopathological Evaluation

“…Our case showed a weak and focal immunoreactivity to COX-2 in less than 10% of neoplastic cells and was considered as a non-COX-2-overexpressing tumor [22,[38][39][40]. Previous studies have described COX-2 expression in SCC of the cornea in horses [23,24]. Since the methodologies, as well as the scoring methods, adopted are different, it is still unclear whether COX-2 plays a role in the development and progression of this type of corneal tumor.…”

“…Since the etiopathogenesis of ocular SCC is still unclear, some authors have evaluated the expression of COX, especially COX-2, in corneal neoplastic tissues of horses and have suggested a possible role of the enzyme in oncogenesis and/or progression of this type of corneal tumor [23,24].…”

“…Only three canine SCCs have been characterized by the use of immunohistochemistry, and p53 protein was generally investigated with varying results [7,9]. Cyclooxygenase (COX) overexpression has been identified in various neoplastic tissues in humans [12][13][14][15][16][17][18] and domestic animals [19][20][21][22][23][24][25][26]. COX-2 has been found to be strongly expressed in all the cases of canine SCC of the cutis [27].…”

Equine periocular neoplasia: Current concepts in aetiopathogenesis and emerging treatment modalities

“…Cycloxygenases are a family of enzymes responsible for conversion of arachidonic acid to prostaglandins and multiple isoforms of COX exist, with COX-1 and COX-2 being the most biologically active (Rassnick and Njaa 2007). Cycloxygenases are a family of enzymes responsible for conversion of arachidonic acid to prostaglandins and multiple isoforms of COX exist, with COX-1 and COX-2 being the most biologically active (Rassnick and Njaa 2007).…”