Abstract 995: Preservation of patient whole blood preserves cancer immune cell biology at single cell resolution

Abstract Blood is an easily accessible clinical sample type that helps inform treatments, investigate disease mechanisms, and monitor outcomes. Logistical challenges in the transportation and processing of blood samples impact data output from single cell RNA sequencing (scRNA-seq). Recent scRNA-seq studies have shown that significant changes in gene expression and immune cell populations occur in as little as a few hours post collection. Thus, there is a need for rapid preservation of blood upon collection before biological changes can occur. Existing preservation approaches compromise the cell membrane, making samples incompatible with single cell transcriptomic analyses. Here, we describe a novel workflow for fixation and long-term storage of whole blood, and isolation of peripheral blood mononuclear cells (PBMCs) from the fixed blood using a readily available, low-cost, high-throughput procedure. We then profile the gene expression of these cells using the fixation-compatible Single Cell Gene Expression Flex workflow. Importantly, this novel blood collection and preparation workflow eases blood transportation logistical constraints, allowing distributed sample collection and batched shipping of blood samples for scRNA-seq and potentially enabling large-scale translational research studies. We compared whole blood fixed immediately after collection using our workflow with clinical blood samples stored at ambient temperature. This revealed that immune cell populations and biological pathways shift significantly as early as five hours following sample collection, if not immediately stabilized. Across a time course of ambient temperature storage of whole blood without immediate stabilization, we observe significant upregulation of stress-related genes (FOS, JUN, CIRBP) in samples using Single Cell Gene Expression Flex profiling. Additionally, expression of a proto-oncogene TNFAIP3 was upregulated in whole blood stored at 20°C compared to samples stored at 4°C for the same lengths of time, unless samples were stabilized using the novel workflow shown here. This novel whole blood fixation method, coupled with automatable cell isolation methods and Single Cell Gene Expression Flex-enabled multiplexed single cell sequencing, will usher in a new age of economical, large-scale translational research studies that result in valuable clinical insights. Citation Format: Kelly Martin, Connor Kunihiro, Jawad Abousoud, Tingsheng Drennon, Yina Li, Sean Marrache, Nandhini Raman, Veronica Rodriguez, Paul Lund, Jens Durruthy Durruthy, Sarah Taylor, Andrew Kohlway, Peter Smibert, Dagmar Walter, Jill Herschleb. Preservation of patient whole blood preserves cancer immune cell biology at single cell resolution abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 995.