Immunohistochemical expression of testin protein in testicular tumours in dogs

Testin (TES), a protein localised in the cytoplasm and belonging to the LIM family of proteins, is part of the cytoskeleton localised along stress fibres and recruited to focal adhesions. It is considered a tumour suppressor protein in humans and decreased TES expression has been shown to increase cell motility and decrease cell-cell contact. In veterinary medicine, TES has only been studied in rat testes and, more recently, also in canine testes. The expression of this protein in testicular tumours is unknown. As the dog has been proposed as an animal model for the study of human testicular tumours, studies on canine TES may provide useful information for both species. Therefore, the purpose of the present study was to demonstrate the expression of TES in the most common types of canine testicular tumours. For this study, paraffin blocks of 166 canine testicular tumours (53 Sertoli cell tumours, 50 Leydig cell tumours, and 63 seminomas) were retrieved from the archive of the Department of Pathology of Wroclaw University of Environmental and Life Sciences. Sections were obtained for complete description of the tumours, confirmation of the histological diagnosis, and immunohistochemical TES antigen location. Sections from 10 normal canine testes were examined as controls. The presence of TES was also demonstrated in fresh tissue from three types of canine testicular tumour. The diagnosis was confirmed in the 166 tumours, and TES was immunohistochemically demonstrated in 98 % of them and in all 10 normal testes. All tumour types had reduced expression of TES, even if not related to the tumour growth pattern or mitotic index, demonstrating that TES expression is reduced in canine as well in human testicular tumours. However, the reduction of TES expression appeared to be moderate, and these features were consistent with the evidence that testicular tumours in dogs are often well-differentiated. A complete understanding of the function of TES in cancer processes requires further investigation, but the relative parallelism between normal and neoplastic cells in well-differentiated, mostly benign testicular tumours provides a good basis for studying TES expression in more aggressive tumours, such as prostatic or urinary tract neoplasms.