Expression of hormone receptors, PTGS2 and KI-67 in canine vaginal tumours

Biomarkers are often used in diagnostics, deciding on possible treat-ment options and assessing the prognosis of tumours. However, lit-tle is known about the characterization of canine vaginal tumours (CVT). Therefore, we investigated the expression of oestrogen re-ceptor alpha (ESR1), progesterone receptor (PGR), prostaglandin- endoperoxide synthase 2 (PTGS2) and KI-67 in CVT by RT-qPCR and immunohistochemistry. Formalin-fixed, paraffine-embedded samples classified histologically (haematoxylin eosin and azan stain-ing) and immunohistochemically (alpha-smooth-muscle-actin) as leiomyoma (LM), leiomyosarcoma (LMS), fibroma or polyp were in-cluded. RNA from tumour tissue only was extracted, and RT-qPCR was performed using primers against ESR1, PR and PTGS2. Whereas mRNA expression of ESR1 and PTGS2 did not differ significantly be-tween LM (n = 7), LMS (n = 7), fibroma (n = 6) and polyp (n = 10), PGR expression did (Kruskal–Wallis, p < .05) with expression being signifi-cantly higher in fibromas than in LMS (Dunn's multiple comparison tests, p < .05). (Semi-)quantitative evaluation of protein expression revealed significant differences between groups (LM: n = 12, LMS: n = 11, fibroma: n = 16, polyp: n= 14) for ESR1, PTGS2 and KI-67 (Kruskal– Wallis, all p < .0001), but not PR. LMS was characterized by the highest KI-67 (p < .01) and lowest ESR1 expression (p < .01) compared to all other CVTs. Besides, KI-67 expression was higher in LMs than in fibromas (p < .05). LMS and LM had more PTGS2 stain-ing compared to fibroma (p < .001) and polyps (p < .0001). Our results provide a first step for a better characterization of CVT, but further research is required.