Evaluation of tyrosine-kinase receptor c-kit mutations, mRNA and protein expression in canine lymphoma: might c-kit represent a therapeutic target?

Proposed Diagnostic Criteria and Classification of Canine Mast Cell Neoplasms: A Consensus Proposal

Mast cell neoplasms are one of the most frequently diagnosed malignancies in dogs. The clinical picture, course, and prognosis vary substantially among patients, depending on the anatomic site, grade and stage of the disease. The most frequently involved organ is the skin, followed by hematopoietic organs (lymph nodes, spleen, liver, and bone marrow) and mucosal sites of the oral cavity and the gastrointestinal tract. In cutaneous mast cell tumors, several grading and staging systems have been introduced. However, no comprehensive classification and no widely accepted diagnostic criteria have been proposed to date. To address these open issues and points we organized a Working Conference on canine mast cell neoplasms in Vienna in 2019. The outcomes of this meeting are summarized in this article. The proposed classification includes cutaneous mast cell tumors and their sub-variants defined by grading- and staging results, mucosal mast cell tumors, extracutaneous/extramucosal mast cell tumors without skin involvement, and mast cell leukemia (MCL). For each of these entities, diagnostic criteria are proposed. Moreover, we have refined grading and staging criteria for mast cell neoplasms in dogs based on consensus discussion. The criteria and classification proposed in this article should greatly facilitate diagnostic evaluation and prognostication in dogs with mast cell neoplasms and should thereby support management of these patients in daily practice and the conduct of clinical trials.

Flow Cytometry in the Diagnosis of Canine B-Cell Lymphoma

B cell lymphoma (BCL) is a heterogeneous group of lymphoid malignancies which comprise the majority of canine lymphomas. Diffuse large B cell lymphoma is the most common lymphoma subtype in dogs but other subtypes (e.g., marginal zone lymphoma, follicular lymphoma, mantle cell lymphoma, and others) have been described. This review aims to explore the use of flow cytometry to refine the diagnosis of canine BCL. Particular emphasis will be given to the possible identification of peculiar immunotypes, putative prognostic markers, staging and minimal residual disease.

Expression frequency of c-kit isoforms and its prognostic potential in canine mammary tumours

KIT is a tyrosine kinase receptor involved in carcinogenesis. Two alternatively spliced transcripts, differed from presence of four amino acids (GNSK) at exon 9 of c-kit, were identified in various human tumours and canine hemangiosarcoma (HSA). The biological function and clinical implications of these isoforms have not yet been elucidated in canine tumours. The current study aimed to validate the expression profile and ultimately to evaluate the correlation of c-kit isoform levels with clinicopathological factors of canine mammary tumours (CMTs). In total, the expression profiles of c-kit isoforms in 196 samples obtained from normal mammary glands (NMGs) of healthy controls and dogs with CMTs, benign and malignant CMTs, and HSAs were determined by polymerase chain reaction (PCR) and quantified via real-time PCR. Overall, the expression levels of the two isoforms were equivalent in NMGs, whereas the GNSK^- /GNSK⁺ ratio sharply increased to 7.44- and 8.33-fold, indicating abundant GNSK^- isoforms in benign and malignant CMTs, respectively. However, a significant decrease in GNSK^- expression was detected in dogs with high-grade malignant CMTs (mCMTs) and with metastatic CMTs compared with expression in those with a lower grade and non-metastatic CMTs. In addition, the median survival time was shorter in mCMT canines with a lower GNSK^- /GNSK⁺ ratio than that in mCMT canines with a higher ratio (899 days vs 1534 days). In conclusion, two c-kit isoforms are ubiquitously expressed with great variability in HSAs and CMTs with both benign and malignant status. The GNSK^- /GNSK⁺ ratio could serve as a prognostic indicator for dogs with mCMTs.

A retrospective study of flow cytometric characterization of suspected extranodal lymphomas in dogs

Flow cytometry (FC) is widely applied to characterize and stage nodal lymphomas in dogs because it has a short turnaround time, requires minimally invasive sampling, and allows contemporary evaluation of neoplastic cells in the primary lesion and of blood and marrow involvement. We investigated advantages and limitations of FC in suspected extranodal lymphomas in dogs. The likelihood of obtaining a suitable FC sample was significantly lower for aspirates of extranodal lesions than for lymph node aspirates. However, we noted no differences among different extranodal lesion sites. We also describe FC results for 39 samples compatible with extranodal lymphoma. A dominant population of large cells was easily identified on morphologic FC scattergrams in many cases. Phenotypic aberrancies were frequently present, mainly in T-cell lymphomas. Lymphoma cells were distinguishable from normal residual lymphocytes in >85% of cases, facilitating the quantification of putative blood and marrow involvement by FC. Despite the high percentage of non-diagnostic samples (32 of 73, >40%), we support the inclusion of FC in the diagnostic workup of suspected extranodal lymphomas in dogs, in conjunction with histopathology. Histopathology is the gold standard for diagnosing lymphoma, provides relevant information, including tissue invasion and epitheliotropism, but has a longer turnaround time.

Detection of Mutations in Selected Proto-Oncogenes of Canine Lymphoma

Lymphomas belong among the most frequently diagnosed tumours of the haematopoietic system in dogs. The clinical manifestations and genetic and molecular basis of canine lymphoma resembles those of human non-Hodgkin lymphoma and therefore it can serve as a suitable model for the study of this disease. Neoplastic diseases are the consequence of a number of genetic and epigenetic changes in somatic cells. One of such changes are gene mutations that can subsequently cause changes in the activity of proto-oncogenes and tumour suppressor genes. The aim of our study was to detect potential mutations in selected exons of proto-oncogenes in DNA isolated from samples of lymphoma obtained from two donors - a Bernese Mountain Dog and a female mongrel. On the basis of literary data descriptions of human and canine haematopoietic neoplastic diseases, our investigations of potential changes in DNA focused on proto- oncogenes C-KIT - exons 8, 17; NRAS - exons 1, 2;FLT3 - exons 14, 15 and 20. The investigated samples were amplified by polymerase chain reaction (PCR) and subjected to sequencing. The DNA sequences were compared with reference sequences in the database Ensembl. The comparison of sequences of the C-KIT gene revealed an A/G transition at the 35th nucleotide of exon 8 in the mongrel. It involved a synonymous exchange of the nucleotide in the codon that did not cause a change in the amino acid. In the same sample we recorded several point mutations in the intron regions surrounding the exons 14 and 20 of the FLT3 gene. Changes in the intron regions can affect the expression of genes and thus can play an important role in the origin and development of tumours. No genetic mutations were detected in any gene regions of the Bernese Mountain Dog. In the case of the NRAS gene, no changes were observed in any sample collected from the donors.

Effects of toceranib phosphate (Palladia) monotherapy on multidrug resistant lymphoma in dogs

We examined whether multidrug resistant (MDR) canine lymphoma increases gene expression for platelet-derived growth factor receptor α (PDGFRα), vascular endothelial growth factor receptor 2 (VEGFR2), and c-KIT, and whether toceranib phosphate (TOC) has potential as a treatment for MDR canine lymphoma. The clinical data showed that PDGFRα expression was higher in canine subjects with MDR T-cell lymphoma than in those with untreated T-cell lymphoma, and that c-KIT expression was greater in subjects with T-cell lymphoma than in those with B-cell lymphoma. TOC monotherapy was well tolerated without serious adverse effects, and two of the five subjects that received TOC exhibited partial responses. The data presented here could contribute to the assessment of TOC-based therapy for dogs with MDR or T-cell lymphoma.

Comprehensive genomic characterization of five canine lymphoid tumor cell lines

BACKGROUND

Leukemia/lymphoma cell lines have been critical in the investigation of the pathogenesis and therapy of hematological malignancies. While human LL cell lines have generally been found to recapitulate the primary tumors from which they were derived, appropriate characterization including cytogenetic and transcriptional assessment is crucial for assessing their clinical predictive value.

RESULTS

In the following study, five canine LL cell lines, CLBL-1, Ema, TL-1 (Nody-1), UL-1, and 3132, were characterized using extensive immunophenotyping, karyotypic analysis, oligonucleotide array comparative genomic hybridization (oaCGH), and gene expression profiling. Genome-wide DNA copy number data from the cell lines were also directly compared with 299 primary canine round cell tumors to determine whether the cell lines represent primary tumors, and, if so, what subtype each most closely resembled.

CONCLUSIONS

Based on integrated analyses, CLBL-1 was classified as B-cell lymphoma, Ema and TL-1 as T-cell lymphoma, and UL-1 as T-cell acute lymphoblastic leukemia. 3132, originally classified as a B-cell lymphoma, was reclassified as a histiocytic sarcoma based on characteristic cytogenomic properties. In combination, these data begin to elucidate the clinical predictive value of these cell lines which will enhance the appropriate selection of in vitro models for future studies of canine hematological malignancies.