Abstract A038 Plasma exosome concentrations in healthy canines and dogs with osteosarcoma

Canine osteosarcoma is a common disease that shares many clinical and biological features with human osteosarcoma. We have previously demonstrated the potential of using mRNA signatures derived from exosome cargo to detect minimal residual disease in dogs undergoing treatment for osteosarcoma. Our goal is to continue exploring the potential of exosomes in cancer diagnosis and treatment by understanding how exosomes contribute to the biology of osteosarcoma. For this study, we compared exosome concentrations in the plasma of 26 healthy dogs and 29 dogs with various cancers, including 8 dogs with osteosarcoma. Dogs with cancer had higher exosome concentrations than the healthy dogs (p=0.0007), as did the subset of dogs with osteosarcoma. Specifically, the average exosome concentration in the samples from healthy dogs was 5x1011 (+/-2.72x1011) particles/mL, with a normal distribution ranging from 7.22x1010 to 1x1012, whereas the average exosome concentration in the samples from dogs with osteosarcoma was 1.14x1012 (+/-1.41x1012) particles/mL, with a non-parametric distribution ranging from 1.16x1011 to 4.4x1012. Ongoing work includes expanding the data set with archival samples, as well as evaluating potential relationships between exosome concentrations and disease-free survival in dogs with osteosarcoma. In conclusion, the difference in plasma exosome concentrations between healthy dogs and dogs with osteosarcoma, and specifically the heterogeneous distribution of exosomes in the plasma of dogs with osteosarcoma suggests that this could be one feature used in combination with analyses of exosome cargo to aid in prognosis and manage treatment of patients with osteosarcoma. Citation Format: Jaron M. Magstadt, Courtney H. Labé, Meagan Wojtysiak, Kyle DuVal, Ali Khammanivong, Lauren J. Mills, Amber Winter, Caitlin Feiock, Kelly Reid, Mitzi Lewellen, Logan G. Spector, Brenda J. Weigel, Jaime F. Modiano, Kelly M. Makielski. Plasma exosome concentrations in healthy canines and dogs with osteosarcoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pediatric Cancer Research; 2024 Sep 5-8; Toronto, Ontario, Canada. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl):Abstract nr A038.