ICCFGG 2022
#9 Concordance of Somatic Mutations between Blood Biopsy and primary tumor samples in Canine Osteosarcoma Christopher Husted1,2 , Kate Megquier1, Michelle White1,2, Heather L. Gardner1,2,3, Viktor Adalsteinsson1, Cheryl A. London1,3, Elinor K. Karlsson1,2 christopher.husted@umassmed.edu 1Broad Institute of MIT and Harvard, Cambridge, MA, USA; 2UMass Chan Medical School, Worcester, MA, USA; 3Tufts University Cummings School of Veterinary Medicine, North Grafton, MA, USA Introduction: Blood biopsy represents an important advancement in cancer diagnostics and patient monitoring. It has the potential to be used as a non-invasive and inexpensive proxy for tumor biopsy, and has been shown to detect relapse prior to the emergence of clinical signs. Studies in human patients have shown concordance between circulating cell-free tumor DNA (ctDNA) and primary tumor tissue biopsies, but this has not yet been evaluated exome-wide in canine samples. Methods: We performed ultra-low-pass whole genome sequencing and whole exome sequencing on banked plasma samples from six dogs diagnosed with osteosarcoma where tumor and normal whole genome sequencing had already been published. We performed simple somatic variant calling in order to assess concordance between patient matched tumor and ctDNA samples Results: An average of 34 (1-56 variants) and 74 SNPs/INDELs (51-90 variants) were identified across the tumor and ctDNA samples, respectively. Tumor and ctDNA samples were highly concor- dant in most patients, with 57% of the SNPs/INDELs (0-89%) in the tumor samples overlapping the ctDNA and 30% of the SNPs/INDELS (0-49%) in the ctDNA overlapping the tumor samples. Conclusions: The study of osteosarcoma in dogs is important due to its rarity in human populations. Identifying actionable mutations could lead to new treatments for both canines and humans. This data supports the promise of dogs as a model for the development of blood biopsy as a tool for detection and patient monitoring in canine and human cancers. #10 Evidence for variability at myxomatous mitral valve risk loci in Australian Cavalier King Charles Spaniels Claire M. Wade1 , Sophie E. Mead1, Niek Beijerink2, and Mitchell O’Brien3 claire.wade@sydney.edu.au 1The University of Sydney, Faculty of Science, School of Life and Environmental Sciences Camperdown, NSW Australia, 2Veterinaire Specialisten Vught, Reutsedijk 8a, Vught, PC, The Netherlands, 3Transformations Bioinformatics, Health and Biosecurity, Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW, Australia The most common cardiopathy in domestic dogs is myxomatous mitral valve disease (MMVD), accounting for 75% of all cardiac disease. An increase in age is generally associated with increased incidence of the disease, but Cavalier King Charles Spaniels (CKCS) exhibit an unusually high prevalence of early-onset MMVD. Previous research has suggested that some candidate risk alleles for MMVD are fixed in the CKCS, including six locations within the nebulette (NEBL) gene on CFA2.
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