Aberrant Expression of E-cadherin/β-catenin During Epidermal Tumourigenesis in Dogs.

Clinically relevant epidermal tumours in dogs include cutaneous papillomas (CPs) and cutaneous squamous cell carcinomas (CSCCs). The development of CPs and CSCCs involves dysregulation in expression of E-cadherin/β-catenin; however, knowledge about the contribution of these molecules to epidermal tumourigenesis in dogs is limited. This study examined the immunohistochemical expression pattern of E-cadherin/β-catenin in samples of normal canine epidermis, CPs, preneoplastic epidermis and CSCCs, using tissue microarrays, in order to elucidate whether the dysregulated expression of these molecules may contribute to the pathogenesis of clinically relevant epidermal tumours in dogs. We also investigated the correlation between the immunohistochemical expression pattern of E-cadherin/β-catenin in these tissue microarrays to further evaluate whether the disruption of the adherens junction interactions plays a relevant role in canine epidermal tumourigenesis. In samples of CP and preneoplastic epidermis, the membrane immunoreactivity of E-cadherin/β-catenin was conserved, while in CSCC, the immunoreactivity of these molecules was significantly reduced, independently of the tumour location. There was significant correlation between the membrane expression of E-cadherin/β-catenin in CSCC. β-catenin also showed cytoplasmic and nuclear expression in samples of CP, preneoplastic epidermis and CSCC. These results support the hypothesis that dysregulated expression of E-cadherin/β-catenin may play a critical role in the pathogenesis of relevant canine epidermal tumours, not only due to the disruption of the intercellular adherens junctions, but also due to the dysregulated activity of the signalling pathways in which these molecules are involved.