Expression of Peroxisome Proliferator‐activated Receptor Gamma (PPAR‐γ) in Canine Nasal Carcinomas

Summary Peroxisome proliferator‐activated receptor γ (PPAR‐γ) is a ligand‐activated transcriptional factor belonging to the steroid receptor superfamily. PPAR‐γ is expressed in multiple normal and neoplastic tissues, such as the breast, colon, lung, ovary and placenta. In addition to adipogenic and anti‐inflammatory effects, PPAR‐γ activation has been shown to be anti‐proliferative by its differentiation‐promoting effect, suggesting that activation of PPAR‐γ may be useful in slowing or arresting the proliferation of de‐differentiated tumour cells. In this study, we investigated the expression of PPAR‐γ in normal and neoplastic canine nasal epithelium. Twenty‐five samples composed of five normal nasal epithelia and 20 canine nasal carcinomas, were immunohistochemically stained for PPAR‐γ. The specificity of the antibody was verified by Western Blot analysis. Confocal laser scanning microscopical investigation was also performed. In normal epithelium, the staining pattern was cytoplasmic and polarized at the cellular free edge. In carcinomas, the neoplastic cells showed mainly strong cytoplasmatic PPAR‐γ expression; moreover, perinuclear immunoreactivity was also detected and few neoplastic cells exhibited a nuclear positivity. Our results demonstrate different patterns of PPAR‐γ expression in normal canine nasal epithelium when compared with canine nasal carcinoma. The importance of this transcription factor in the pathophysiology of several different tumours has stimulated much research in this field and has opened new opportunities for the treatment of the tumours.