Potential Blood and Tissue Protein Biomarkers of Canine Mammary Gland Tumours – A Review*

Canine mammary tumours (CMTs) represent one of the most common neoplastic conditions in dogs, occurring predominantly in intact females. Despite being a well-recognised issue for several decades, effective tools for the early detection of CMTs remain limited. Investigating tumour-associated biomarker proteins through quantitative and qualitative approaches may provide solutions to this diagnostic challenge. While some biomarkers for mammary tumours have been extensively studied in both human and veterinary medicine, this article focuses on describing less explored but potentially valuable proteins for diagnostic and prognostic purposes in dogs with CMTs. The studies collected primarily involve proteomic analyses of blood and tumour tissue samples collected from dogs with CMTs. Key proteins discussed include immune system proteins (e.g. interleukins), protein receptors (e.g. vitamin D receptor), signalling pathway proteins (e.g. Hedgehog signalling pathway proteins), membrane channel proteins (aquaporins) and extracellular matrix proteins (periostin and decorin). In addition to individual proteins, large-scale proteomic studies showing the broad CMT proteome and the potential of using autoantibodies as a diagnostic panel are discussed. Furthermore, four distinct patterns of protein expression changes relevant to CMTs are described, i.e. benign, malignant, non-metastatic, metastatic and linear expression profiles. Nonetheless, the current findings provide a strong foundation for future, more comprehensive research.