Abstract A051: Identifying patterns of cell-free DNA associated with elevated risk of diffuse large B-cell lymphoma in adult dogs
Authors: Burt Lauren E , Treeful Amy E , Lewellen Mitzi , Demos-Davies Kimberly , Chehadeh Andrea , Pracht Sara , Schulte Ashley J , Feiock Caitlin , Medland Julia , Seelig Davis , Makielski Kelly M , Khammanivong Ali , Borgatti Antonella , Henson Michael S , Linden Michael , Vallera Daniel , Cutter Gary R , Sarver Aaron L , Modiano Jaime F 
Published: November 2024

Abstract
Background: Nonrandom patterns of cell-free DNA (cfDNA) are closely associated with malignancy. We hypothesize that they are also found in the systemic microenvironment that gives rise to cancer, and that such signatures can inform a risk stratification test. To achieve this, we have initiated the Lymphoma Risk Assessment (LyRA) study, using machine learning on a training set of dogs with known health status and a test set of otherwise healthy adult pet dogs to identify cfDNA signatures that are associated with elevated risk of developing diffuse large B- cell lymphoma (DLBCL). We will validate the predictive accuracy of these signatures, including the persistence of the risk environment and the interval between risk detection and development of clinical disease. Since cfDNA is the primary input of the LyRA test, we first performed a pilot study to assess how sample characteristics affect cfDNA quality and subsequent low-pass whole genome sequencing (WGS) data. Methods: Blood samples were collected from pet dogs with the owner’s informed consent. Paired samples were collected into potassium (K3)EDTA tubes and additive-free red top tubes (n = 5 dogs) or K3EDTA tubes and Cell-free DNA BCT® Streck Tubes (n = 6 dogs). Additional serum samples (n=3) were generously provided by the Morris Animal Foundation Golden Retriever Lifetime Study. cfDNA was isolated using the QIAamp® Circulating Nucleic Acid kit. Total cfDNA concentration was measured by PicoGreen™ and fragment distribution by Agilent High Sensitivity D500 ScreenTape® Assay, with comparisons made by starting material (plasma vs. serum) and collection tubes. Results: Serum had both higher total concentrations of cfDNA (PicoGreen™) and calibrated concentrations of long fragment cfDNA (515-658 bp Agilent traces) compared to plasma. In addition, total cfDNA concentrations increased with malignancy, following the pattern: no cancer &lt; cancer &lt; hematological cancer. Median fragment lengths of Agilent peaks also increased with malignancy for short (125-181 bp) and medium (340-425 bp) fragments, in both serum and plasma, but decreased for long fragments. In these pilot data the trends seen were consistent with our hypothesis and with prior studies, although due to sample size, no statistical testing was performed. Conclusions: The pilot study demonstrated that the effects of sample parameters on cfDNA quality are consistent with existing literature, validating our methods and supporting the rationale for the LyRA study. These features may prove valuable when integrated with genomic data to identify high-risk microenvironments. Recent research has shown that a majority of cfDNA in tumor patients originates from non-malignant cells and current methods often overlook potentially important patterns in this so-called 'discard cfDNA.' By focusing on these overlooked patterns, with an emphasis on risk stratification, the LyRA test could shift clinical management to a prevention-focused approach, serving as a model of testing and interception for DLBCL and other cancers in dogs, and potentially in humans.
Citation Format: Lauren E Burt, Amy E Treeful, Mitzi Lewellen, Kimberly Demos-Davies, Andrea Chehadeh, Sara Pracht, Ashley J Schulte, Caitlin Feiock, Julia Medland, Davis Seelig, Kelly M Makielski, Ali Khammanivong, Antonella Borgatti, Michael S Henson, Michael Linden, Daniel Vallera, Gary R Cutter, Aaron L Sarver, Jaime F Modiano. Identifying patterns of cell-free DNA associated with elevated risk of diffuse large B-cell lymphoma in adult dogs [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr A051.