Abstract A036: Next gen liquid biopsy: Comprehensive analysis from a single tube of blood

Abstract Introduction There remains a largely untapped potential for utilizing liquid biopsy as a non- invasive, real-time window into tumor biology. In this study, we report on the use of the high- multiplex protein quantitation capability of the OrionTM spatial biology platform (RareCyte®, Inc) and cell picking capability of the CyteFinder® rare cell platform, to perform a comprehensive liquid biopsy analysis of whole blood that provides a deeper understanding of samples. This novel technology was used to characterize circulating tumor cells (CTCs), perform immune profiling of white blood cells (WBCs), and perform targeted mutation profiling of CTCs and cell-free DNA (cfDNA). All of these analytes can be measured from one 7.5 mL draw of blood. This array of tests was applied to cancer samples to demonstrate clinical feasibility. MethodsBlood samples were collected into AccuCyte® blood collection tubes. Buffy coats were processed to microscope slides using AccuCyte® blood processing kits. Slides were fixed and stained with an 18-plex immuno-oncology panel and imaged using the Orion Spatial Biology platform to evaluate protein biomarker expression on CTCs and to profile WBCs. Individual CTCs and WBCs from clinical samples were isolated using the CytePicker® for downstream molecular analysis. cfDNA was isolated from plasma collected during the AccuCyte process. Picked CTCs, WBCs, and cfDNA were sequenced using the CleanPlex® OncoZoom® Cancer Hotspot Kit. ResultsCancer patient blood was tested with a high-plex immunofluorescence assay using the Orion spatial biology system. CTCs were identified and phenotypically characterized in multiple cancer types. On the same slides, immunophenotyping of WBCs was performed. T- cell, B-cell, and macrophage populations were quantified. Additional sub-populations of T-cells (regulatory and memory) and proliferating cells (Ki67+) were enumerated. Expression of checkpoint-specific markers PD-L1 and PD-1 was measured on CTCs and WBCs. Sequencing results from individual picked CTCs showed evidence of minor clones representative of tumor heterogeneity that were not detectable in the cfDNA analysis. Conclusions This novel application of a high-plex spatial biology imaging system to liquid biopsies, in conjunction with the proven capabilities of rare cell detection and genomic analysis of single cells and cfDNA, has the potential to revolutionize liquid biopsy testing. From a single blood sample, this approach allows one to ask important questions about the complex interactions between the immune system and the tumor and to follow these interactions longitudinally in real time over the course of the disease. The goal is to leverage this unprecedented depth of analysis to improve patient outcomes and better understand the biological complexity of disease. Future directions of this work are to study rare types of WBCs that indicate immune activation and response to the tumor, and the detection and longitudinal monitoring of cell therapies such as CAR T cells after infusion. Citation Format: Arturo B Ramirez, Jon Ladd, Erin Bayer, Brock Bartels, Rachel Ponting, Arista Tischner. Next gen liquid biopsy: Comprehensive analysis from a single tube of blood [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 A036.