Liquid biopsy based on small extracellular vesicles predicts chemotherapy response of canine multicentric lymphomas.

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.

Identification of two molecular subtypes in canine mast cell tumours through gene expression profiling.

Mast cell tumours (MCTs) are common neoplasms in dogs and are usually regarded as potentially malignant. Several studies have attempted to identify biomarkers to better predict biological behaviours for this tumour. The aim of this study was to identify pathways connected to clinical and histopathological malignancies, shorter survival times, and poor prognoses associated with MCTs. We performed genome-wide gene expression analyses on tissues obtained from 15 dogs with single MCTs, and identified two distinct tumour subtypes-high-risk and low-risk-associated with differences in histological grades, survival times, Ki67 indices, and occurrence of death due the disease. Comparative analyses of RNA sequence profiles revealed 71 genes that were differentially expressed between high- and low-risk MCTs. In addition to these analyses, we also examined gene co-expression networks to explore the biological functions of the identified genes. The network construction revealed 63 gene modules, of which 4 were significantly associated with the more aggressive tumour group. Two of the gene modules positively correlated with high-risk MCTs were also associated with cell proliferation and extracellular matrix-related terms. At the top of the extracellular matrix module category, genes with functions directly related to those of cancer-associated fibroblasts (CAFs) were identified. Immunohistochemical analyses also revealed a greater number of CAFs in high-risk MCTs. This study provides a method for the molecular characterisation of canine MCTs into two distinct subtypes. Our data indicate that proliferation pathways are significantly involved in malignant tumour behaviours, which are known to be relevant for the induction and maintenance of MCTs. Finally, animals presenting high-risk MCTs overexpress genes associated with the extracellular matrix that can be robustly linked to CAF functions. We suggest that CAFs in the MCT stroma contribute to cancer progression.

Intratumoral collagen index predicts mortality and survival in canine cutaneous mast cell tumours.

BACKGROUND: Mast cell tumours (MCTs) constitute almost 25% of cutaneous neoplasms in dogs. Their biological behaviour is predicted using histopathological grading which is based on several subjective criteria that are vulnerable to intra- and interobserver variability. To improve the prediction of the biological behaviour, several complementary markers have been studied. The integrity of the extracellular matrix (ECM) may play a protective role against tumoral progression, and favour cellular proliferation, angiogenesis, invasion and metastases when altered. HYPOTHESIS/OBJECTIVES: To evaluate the quantification of collagen and elastic fibres as prognostic markers for MCTs. ANIMALS: Thirty-eight random cases of canine cutaneous MCT surgically treated with wide margins were included. METHODS AND MATERIALS: Intratumoral collagen and elastic fibres were identified and quantified on histological sections stained with Masson's trichrome, Picrosirius red and Verhoeff; the results were compared with histopathological grades, mortality due to the disease and postsurgical survival. RESULTS: Morphometric analysis revealed a significant relationship between histopathological grade and intratumoral collagen index (CoI). In addition, the CoI was considered an independent indicator for mortality and postsurgical survival. CONCLUSIONS AND CLINICAL IMPORTANCE: These results support the importance of the CoI in the grading and prognosis of MCTs, suggesting that preservation and/or synthesis of collagen have the potential to become targets for MCT therapeutics.

Nanog Expression and Proliferation Indices in Canine Cutaneous Mast Cell Tumors.

Mast cell tumors are one of the most frequent skin tumors in dogs. Treatment decisions often depend on a wide range of clinical information and the main criteria for prognostic formulation are histological grade, mitotic count, Ki67 index, and KIT immunostaining pattern. NANOG is a pluripotency factor expressed by normal and cancer stem cells, which is a prognostic marker and a potential therapeutic target for several human tumors. In the present study, mast cell tumor samples from 41 dogs were evaluated for NANOG and Ki67 by immunohistochemistry. All samples were positive for NANOG but its expression was not correlated with Ki67 index and no significant differences were found with respect to histopathological grades, disease-related mortality, or survival. Our results suggest that, although related to pluripotency, NANOG expression does not correlate with proliferative activity, and is not a reliable prognostic factor for canine cutaneous mast cell tumors.