The expression ratio of miR-17-5p and miR-155 correlates with grading in canine splenic lymphoma

In dogs as in humans, microRNAs (miRNAs) play a key role in normal and neoplastic hematopoiesis regulation. The general miRNA expression framework varies among different stages of development and differentiation of tumors, and miRNAs are widely investigated as new molecular tools for cancer diagnosis and classification. Canine lymphomas are currently classified according with the WHO classification, but a comprehensive grading study of clinical samples is still lacking, and molecular tools for quick grading are not yet available. In the present work, a retrospective study of the expression profile of a panel of miRNAs in canine primary splenic lymphomas was performed. The formalin fixed, paraffin embedded (FFPE) lymphoma samples were accurately classified according with the WHO classification, and were analyzed for miRNA expression using stem-loop TaqMan real time RT-PCR. For each miRNA investigated, relative and absolute quantification were performed after selecting the best housekeeping genes using the NormFinder and geNorm algorithms. The results of this study show a diversity in miRNA expression in low (L) grade lymphomas compared to intermediate-high (I-H) grade lymphomas. The molar ratio between miR-17-5p and miR-155 correlated with WHO grading. These results highlight the potential use of miR-17-5p/miR-155 molar ratio as a new molecular tool for grading of canine splenic lymphomas. The data here reported further support the utility of monitoring miRNA expression in canine hematopoietic malignancies diagnosis and prognosis.