Lymphoma is the most common type of canine hematological malignancy where the multicentric (cMCL) form accounts for 75% of all cases. The standard treatment is the CHOP chemotherapy protocols that include cyclophosphamide, doxorubicin, vincristine and prednisone, where the majority of dogs achieve complete/partial response; however, it is very important to predict non-responsive cases to improve treatment and to develop new targeted therapies. Here we evaluate a liquid biopsy approach based on serum Small Extracellular Vesicles enriched for exosomes (SEVs) to predict cMCL chemotherapy response. Nineteen dogs at the end of the 19-week chemotherapy protocol (8 Complete Response and 11 Progressive Disease) were evaluated for serum SEVs size, concentration and screened for 95 oncomirs. PD patients had higher SEVs concentration at the diagnosis than CR patients (P = 0.034). The ROC curve was significant for SEVs concentration to predict the response to CHOP (AUC = 0.8011, P = 0.0287). A potential molecular signature based on oncomirs from SEVs (caf-miR-205, caf-miR-222, caf-mir-20a and caf-miR-93) is proposed. To the best of our knowledge, this is the first study demonstrating the potential of a liquid biopsy based on SEVs and their miRNAs content to predict the outcome of chemotherapy for canine multicentric lymphomas.

Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoma in dogs. We evaluated Ki67 immunoexpression and mitotic index (MI) in dogs diagnosed with DLBCL and treated with a 19-wk CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) protocol. Twenty-nine lymph node samples from dogs diagnosed with DLBCL were analyzed for Ki67 immunostaining, and positive cells present in 1 cm were counted in a grid reticle for comparison of survival times above and below the means. The Ki67 mean was 107, and the MI mean was 21. There was a significant ( p < 0.05) difference in median survival time between Ki67 immunostaining above and below the mean, with no difference in MI groups. Ki67 values >107 positive cells per 5 HPF counted in a grid reticle were associated with shorter survival times in dogs with DLBCL treated with a 19-wk CHOP-based protocol.