LAUSR

Histiocytic sarcoma (HS) is a rare human hematopoietic neoplasm that accounts for less than 1% of hematolymphoid cancers and occurs either concurrently with or subsequently to B- or T-lymphoblastic lymphoma and other B-cell cancers. As such, its genetic etiology has been difficult to establish. HS in dogs, by comparison, shows strong breed specificity with 20% of flat-coated retrievers and 25% of Bernese mountain dogs (BMD) estimated to develop the disease in their lifetime. These two affected breeds share no recent common ancestors and display differences in disease presentation, offering a unique system in which to investigate the genetic predisposition and progression of HS. Our lab has previously undertaken genome wide association study (GWAS) on both BMD and FCR collected in North America and Europe and identified four significantly associated loci, two in BMD and two in FCR. In each breed, only one locus was segregating with disease in the American population while both were present in the European populations. There were no loci in common between the two breeds. Fine mapping of the common BMD HS locus on canine chromosome (CFA) CFA11 revealed a single haplotype spanning the MTAP (methylthioadenosine phosphorylase) gene and part of the cyclin-dependent kinase inhibitor 2A (CDKN2A) gene, which was present in 96% of BMD with HS. The European BMD also showed a significant locus on CFA14 that may be approaching fixation in the American dogs based on allele frequency calculations. We have done targeted resequencing of the CFA14 locus in a subset of European BMD and are in the process of filtering the identified mutations. Promising candidate genes in this region include GRM8, which inhibits the cyclic AMP cascade in the central nervous system and has shown to be involved in several of cancers; POT1, which is involved in telomere length maintenance and protection; and HYAL4, a hyaluronidase potentially involved in extracellular matrix degradation. In addition, the laboratory has generated 30x sequence from two HS cases and a control BMD, two FCR cases, and a control and low pass sequence from 16 dogs (8 cases and controls) in order to identify the likely causative mutations in each of the associated loci as well as breed specific mutations that may predispose the dogs to aggressive cancers. Citation Format: Heidi G. Parker, Edouard Cadieu, Abigail Shearin, Gerard Rutteman, Elaine A. Ostrander. Analysis of a histiocytic carcinoma in the dog: The canine9s utility in fetching disease genes [abstract]. In: Proceedings of the AACR Conference on Advances in Sarcomas: From Basic Science to Clinical Translation; May 16-19, 2017; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(2_Suppl):Abstract nr IA08.