Abstract IA005: Tumor cell-based liquid biopsy to characterize prostate cancer

Abstract Circulating Tumor Cells (CTCs) hold the promise of comprehensive yet noninvasive molecular characterization of cancer cells during the course of tumor evolution and progression. To dissect the epigenetic profile of prostate CTCs, we undertook paired DNA methylation and RNA sequencing of single CTCs isolated from blood specimens of patients with prostate cancer. Across the genome, our study identified 40 core Partial Methylation Domains (PMDs) that arise early in tumorigenesis and are shared by all individual CTCs across multiple patients. Key among these is a single genomic locus harboring multiple interferon-inducible genes along with all the CD1 gene family members, implicated in innate immunity. Based on mouse models, we propose that early biallelic silencing of multiple genes residing within a single PMD may contribute to the escape from immune surveillance in prostate and potentially other cancers. Studies of CTC heterogeneity within individual patients are limited by the very small number of cells that can be isolated from standard 10ml blood volumes. To enable such analyses, we applied a new high throughput microfluidic platform, capable of processing an entire leukapheresis product, interrogating 2-3 L of blood volume equivalent. Applying this technology to patients with metastatic prostate cancer, we successfully enriched thousands of CTCs from individual cases, enabling the characterization of intra-patient heterogeneity at the level of cell morphology and marker expression, chromosome copy number variation and exome-wide genotyping, and transcriptionally-defined tumor cell subpopulations. Such high-volume microfluidic enrichment of CTCs constitutes a new dimension in liquid biopsies. Citation Format: Daniel A Haber, Shyamala Maheswaran, Hongshan Guo, Joanna Vuille, Shih-Bo Huang, Ben S Wittner, Lecia V Sequist, Richard J Lee, Patricia AR Brunker, David T Miyamoto, Avanish Mishra, Mehmet Toner. Tumor cell-based liquid biopsy to characterize prostate cancer [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 IA005.