RT Journal Article SR Electronic T1 Development of an exosomal biomarker signature to detect minimal residual disease in dogs with osteosarcoma using a novel xenograft platform and machine learning JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.02.11.429432 DO 10.1101/2021.02.11.429432 A1 Kelly M. Makielski A1 Alicia J. Donnelly A1 Ali Khammanivong A1 Milcah C. Scott A1 Andrea R. Ortiz A1 Dana C. Galvan A1 Hirotaka Tomiyasu A1 Clarissa Amaya A1 Kristi Ward A1 Alexa Montoya A1 John R. Garbe A1 Lauren J. Mills A1 Gary R. Cutter A1 Joelle M. Fenger A1 William C. Kisseberth A1 Timothy D. O’Brien A1 Logan G. Spector A1 Brad A. Bryan A1 Subbaya Subramanian A1 Jaime F. Modiano YR 2021 UL http://biorxiv.org/content/early/2021/02/12/2021.02.11.429432.abstract AB Osteosarcoma has a guarded prognosis. A major hurdle in developing more effective osteosarcoma therapies is the lack of disease-specific biomarkers to predict risk, prognosis, or therapeutic response. Exosomes are secreted extracellular microvesicles emerging as powerful diagnostic tools. However, their clinical application is precluded by challenges in identifying disease-associated cargo from the vastly larger background of normal exosome cargo. We developed a method using canine osteosarcoma in mouse xenografts to distinguish tumor-derived from host-response exosomal mRNAs. The model allows for the identification of canine osteosarcoma-specific gene signatures by RNA sequencing and a species-differentiating bioinformatics pipeline. An osteosarcoma-associated signature consisting of five gene transcripts (SKA2, NEU1, PAF1, PSMG2, and NOB1) was validated in dogs with spontaneous osteosarcoma by qRT-PCR, while a machine learning model assigned dogs into healthy or disease groups. Serum/plasma exosomes were isolated from 53 dogs in distinct clinical groups (“healthy”, “osteosarcoma”, “other bone tumor”, or “non-neoplastic disease”). Pre-treatment samples from osteosarcoma cases were used as the training set and a validation set from post-treatment samples was used for testing, classifying as “osteosarcoma–detected” or “osteosarcoma–NOT detected”. Dogs in a validation set whose post-treatment samples were classified as “osteosarcoma–NOT detected” had longer remissions, up to 15 months after treatment. In conclusion, we identified a gene signature predictive of molecular remissions with potential applications in the early detection and minimal residual disease settings. These results provide proof-of-concept for our discovery platform and its utilization in future studies to inform cancer risk, diagnosis, prognosis, and therapeutic response.Competing Interest StatementThe authors declare that patent Identifying Presence and Composition of Cell Free Nucleic Acids, related to this work and listing Milcah C. Scott, John R. Garbe, and Jaime F. Modiano as inventors has been filed by the Office of Technology Commercialization of the University of Minnesota. US Patent Application 15/783,776 filed on October 13, 2017 The authors declare that patent Biological Status Determination Using Cell-Free Nucleic Acids, related to this work and listing Kelly M. Makielski, Alicia J. Donnelly, Ali Khammanivong, Milcah C. Scott, Hiro Tomiyasu, and Jaime F. Modiano as inventors has been filed by the Office of Technology Commercialization of the University of Minnesota. US Patent Application 16/600,486 filed on October 12, 2019