760: Cellular Genomics - Molecular Cytogenetic Investigation of Canine Soft Tissue Sarcomas
Grant Status: Closed
Histiocytic malignancies, often referred to as histiocytic sarcoma (HS) and/or malignant histiocytosis (MH) are of major health concern to a variety of breeds, including Bernese Mountain Dog and Flat coated Retriever. In this project we aimed to recruit and analyze 75 cases of MH/HS from these two breeds, using genome-wide array based comparative genomic hybridization (aCGH), multicolour fluorescence in situ hybridization (FISH) analysis and loss of heterozygosity (LOH) analysis. Importantly, this study included BMDs from both the USA and from France. As such we were able to determine that there are no significant differences the genome wide aberrations profiles of either population, suggesting that the Berner populations of the USA and Europe may be considered as a single large population for the purpose of genetic investigations. Due to additional resources becoming available, we were able to evaluate a total of 133 cases of MH/HS from BMDs and FCRs, and identify numerous recurrent DNA copy number that are shared between these breeds and unique to each breed, The regions of the genome recurrently involved have been interrogated and contain several key genes that are known to be associated with the cancer process. The data in this study revealed several key findings: 1) MH/HS from BMDs resident in the USA and in France have recurrent DNA copy number changes that do not differ significantly, suggesting that the strong association between breed and disease type is not affected by the gene pool of the breed. This indicates that we may be able to consider the BMDs in USA and Europe as a single population. Importantly, as we develop new treatments for this devastating cancer, they likely will apply to all BMDs with MH/HS, regardless of geographic origin. 2) Analysis of histiocytic malignancies from BMDs and FCRs indicates that, in general, there is a gross level of shared genetic changes, with 23 regions across both breeds being recurrent in >30% of the cases. The five most frequently occurring shared regions were highly recurrent in each breed (present in >50% of the cases) and so these data suggest that there is a strong association between genomic change and histiocytic malignancies. 3) At least three of these five highly recurrent shared regions contain genes that are known to be associated with cancers. 4) This study detected 13 aberrant region of the canine genome (on seven different chromosomes) that are significantly associated with the presence of HS affecting either internal organs or just a limb. This association also separated breed (BMD 'vs' FCR) and so it is not possible to determine if there is a correlation between 1) breed and cytogenetic profile, or between 2) anatomical location of the MH tumors internal masses and cytogenetic profiles, since there is such a strong association between BMDs and the presence of internal masses. To resolve this we would need to investigate the cytogenetic profiles of other breeds that present with internal MH masses. Further analysis would allow us to determine if it mass location or breed that drives the cytogenetic profiles. 5) Analysis of 25 cases of hemangiosarcoma in a range of breeds, using 1Mb resolution aCGH analysis, revealed the presence of highly chaotic genome reorganization. Many of the chromosome changes present are shared with other cancers, but we are unable to form any concrete conclusions about breed association or disease association without further case analysis. The next phase of this investigation will be to evaluate the status of the genes we have identified to be in regions of significance, both in affected and unaffected individuals.
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