Expression of E-cadherin, beta-catenin and APC protein in canine colorectal tumours.

The present study aimed at evaluating, through immunohistochemical staining, E-cadherin, beta-catenin and adenomatous polyposis coli (APC) expression and distribution in normal, dysplastic and neoplastic canine colon and rectum, and at correlating the protein expression with the histological grade of malignancy. In order to obtain a more thorough evaluation of the APC/beta catenin complex, both proteins were also assessed for colocalization in neoplastic cells through double immunofluorescence staining. Immunohistochemical investigation showed a marked decrease of E-cadherin and APC expression in malignant tumours, while a lack of membranous beta-catenin distribution and a cytoplasmic positivity, rather than a decrease of expression, was observed in less differentiated carcinomas. Confocal laser microscopical observation showed cytoplasmic beta-catenin distribution solely in APC-negative cells, demonstrating that the correct beta-catenin distribution on the cell membrane can be APC dependent, as in human colorectal carcinomas. Therefore, the changes in adhesion molecules can play a very important role both in colorectal carcinogenesis and in malignant progression; moreover, these proteins can also be considered powerful prognostic tools in veterinary oncology.