An Overview of Epithelial-to-Mesenchymal Transition and Mesenchymal-to-Epithelial Transition in Canine Tumors: How Far Have We Come?

SIMPLE SUMMARY: This review deals with the general notion of EMT and the main factors regulating this process, including transcription factors, microRNAs, reactive oxygen species, exosomes, microvesicles, and viruses. Articles dealing with EMT in embryonic life, EMT in fibrosis, as well as in cancer metastasis are discussed, including those dealing with EMT and the tumor microenvironment, pre-metastatic niches, and cancer stem cells. Subsequently, a more in depth analysis of articles reporting EMT in relevant epithelial cancers such as mammary gland carcinomas, prostatic carcinomas, and others is provided. Articles that reported results on the use of EMT as a prognostic marker are also selected and discussed. In addition, the general notion of MET and, in more detail, of MET in sarcomas is discussed. Finally, the use of therapeutic approaches for EMT and MET is addressed. ABSTRACT: Historically, pre-clinical and clinical studies in human medicine have provided new insights, pushing forward the contemporary knowledge. The new results represented a motivation for investigators in specific fields of veterinary medicine, who addressed the same research topics from different perspectives in studies based on experimental and spontaneous animal disease models. The study of different pheno-genotypic contexts contributes to the confirmation of translational models of pathologic mechanisms. This review provides an overview of EMT and MET processes in both human and canine species. While human medicine rapidly advances, having a large amount of information available, veterinary medicine is not at the same level. This situation should provide motivation for the veterinary medicine research field, to apply the knowledge on humans to research in pets. By merging the knowledge of these two disciplines, better and faster results can be achieved, thus improving human and canine health.