01557: Narrowing the Search for the Genetic Basis of Histiocytic Malignancies
Grant Status: Closed
This project has been completed. During this time we have performed all the experimental work that was planned for this phase of the project and are on schedule. Data representing high-resolution genome-wide assessment of DNA copy number changes have been obtained for all 50 cases of histiocytic malignancy (HM) we proposed, 25 each of Bernese mountain dog and flat-coated retriever. In addition we have generated data representing 20 cases of HM across three additional breeds, golden retriever, Labrador retriever and rottweiler. These data indicate that while there is a high degree of similarity between the genome-wide copy number profiles of four breeds, the golden retriever presents with a lower level of complexity in the extent of genome wide aberrations.
These data provided the basis for a custom-generated gene expression assay using the NanoString™ platform. Upon further assessment, we found that deregulation of DNA damage repair pathways and deregulation of the mitotic-spindle assembly was readily apparent in cases of canine HM compared to controls. These findings serve to explain, at least in part, the overall complexity of canine HM at the genomic level. Additionally, we found an increased expression of the well-characterized gene Matrix-metalloproteinase 9 (MMP-9), which has been shown to be involved in tumor progression and metastasis in human medicine. Further, we demonstrated that this increase in mRNA expression corresponded to a significant increase in MMP-9 protein levels. This protein may be responsible for the extreme tumor aggression seen in canine HM, particularly in the disseminated form. Of particular interest is the fact that a clinical trial of a monoclonal antibody directed against MMP-9 is currently underway in human medicine (Clinical trial identifier NCT018-3282).
We also have worked with human pathologists to determine the human counterpart of canine histiocytic sarcoma. A comparative histopathologic study, led by a team of experienced human pathologists, indicated that if the specimens were from the a human patient, canine HS would be diagnosed as an undifferentiated pleomorphic sarcoma (UPS), formerly known as malignant fibrous histiocytoma (MFH). These pathology data allowed us to move forward an assess genome wide copy number aberrations in human UPS (a very rare condition), which demonstrated broad similarity between the diseases, and the significant shared losses of the PTEN, MTAP/CDKN2A/B loci as well as other regions of the genome.
In parallel to the aims of this study, we have used the data to compare the genome wide changes evident in canine HMs with those present in canine lymphoma. This identified three small regions of the dog genome that collectively allowed us to propose a genetic test with >97% accuracy to separate HM from lymphoma, and 94% accuracy in separating HM from lymphoma and hemangiosarcoma. We are pursuing this with a view to releasing an assay that may be used to aid veterinarians and pathologists in avoiding inaccurate diagnoses.
We would like to thank the CHF and the donors to this project for their confidence in our ability to deliver the goals of this study. This is a project that has resulted in far more progress than we initially anticipated and we are delighted to be able to recognize the CHF as the funding source for the reach that this study will have. This award also helped to support Ms. Kennedy through her PhD studies and so we extend additional thanks for providing her that opportunity.
Kennedy, K., Thomas, R., & Breen, M. (2016). Canine Histiocytic Malignancies—Challenges and Opportunities. Veterinary Sciences, 3(1), 2. https://doi.org/10.3390/vetsci3010002
Kennedy, K., Thomas, R., Durrant, J., Jiang, T., Motsinger-Reif, A., & Breen, M. (2019). Genome-wide DNA copy number analysis and targeted transcriptional analysis of canine histiocytic malignancies identifies diagnostic signatures and highlights disruption of spindle assembly complex. Chromosome Research. https://doi.org/10.1007/s10577-019-09606-0
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