miRNA Profiles of Canine Intestinal Carcinomas, Lymphomas and Enteritis Analysed by Digital Droplet PCR from FFPE Material

SIMPLE SUMMARY: Carcinomas and lymphomas are the most common intestinal tumours in dogs. To distinguish them from each other and from intestinal inflammation, non-invasive biomarkers such as microRNAs would be helpful. In this study, miRNA expression of two oncogenic miRNAs (miR-18b, 20b), two tumour-suppressive miRNAs (miR-192, 194) and two potential biomarkers (miR-126, 214) in carcinomas, lymphomas, enteritis and normal tissue of the small and large intestine were measured. Significant shifts in miRNA expression patterns were observed between the groups. However, the expected dysregulation of miR-18b, 20b, 126 and 214 was not found in all tissues. Further studies are needed to clarify the role of different miRNAs in various types of tissue and cancer. ABSTRACT: Most canine intestinal tumours are B-cell or T-cell lymphomas or carcinomas. They have to be distinguished from cases of enteritis. Non-invasive biomarkers such as miRNAs would be a step towards faster diagnosis. The aim of this study was to investigate shifts in miRNA expression in tissue samples collected from cases of enteritis, carcinoma and lymphoma of the small and large intestine to better understand the potential of miRNA as biomarkers for tumour diagnosis and classification. We selected two oncogenic miRNAs (miR-18b and 20b), two tumour suppressive miRNAs (miR-192 and 194) and two potential biomarkers for neoplasms (miR-126 and 214). They were isolated from FFPE material, quantified by ddPCR, normalised with RNU6B and compared with normal tissue values. Our results confirmed that ddPCR is a suitable method for quantifying miRNA from FFPE material. Expression of miR-18b and miR-192 was higher in carcinomas of the small intestine than in those of the large intestine. Specific miRNA patterns were observed in cases of enteritis, B-cell and T-cell lymphoma and carcinoma. However, oncogenic miR-18b and 20b were not elevated in any group and miR-126 and 214 were down-regulated in T-cell and B-cell lymphoma, as well as in carcinomas and lymphoplasmacytic enteritis of the small intestine.