Abstract 2287: Circulating extracellular vesicles from patients with advanced pancreatic cancer contain low levels of tumor-derived DNA

Abstract

Abstract Purpose: Extracellular vesicles (EVs) have been shown to contain nucleic acids, including DNA. Several studies have highlighted the potential of EV-derived DNA (evDNA) as a circulating biomarker, even demonstrating that evDNA can outperform circulating cell-free DNA (cfDNA) in terms of sensitivity. Here, we evaluated whether EVs could be a potential source of tumor-derived DNA in patients with advanced pancreatic cancer. Methods: evDNA from both DNase-treated and untreated circulating EVs, enriched from patients with advanced pancreatic cancer (n=10), was analyzed by fluorometry and digital droplet PCR to determine the level of evDNA inside and outside (surface-bound) the EVs. To also determine if choice of methodology affected the results, EVs were isolated using four different small EV isolation methods (differential ultracentrifugation, size-exclusion chromatography, affinity purification and precipitation) and differential centrifugation for isolation of large EVs. Western blotting, dynamic light scattering and transmission electron microscopy confirmed the enrichment of EVs. Results: Our results indicated that EVs enriched from patient blood samples contained significantly lower amounts of DNA compared to cfDNA (p < 0.001); >50-fold lower for untreated sEVs and >1000-fold lower for DNase-treated EVs. Thus, most of the detected vesicle-associated DNA seemed to be located outside of the vesicles. Further, tumor-derived DNA in EVs was barely detectable and the tumor-derived fraction in all evDNA samples was similar to that of cfDNA. Conclusion: Our results demonstrated that evDNA do not add any extra information compared with cfDNA as a source of tumor-derived DNA, at least not in patients with advanced pancreatic cancer. Citation Format: Morten Lapin, Kjersti Tjensvoll, Karoline Nedrebø, Eline Taksdal, Hans Janssen, Bjørnar Gilje, Oddmund Nordgard. Circulating extracellular vesicles from patients with advanced pancreatic cancer contain low levels of tumor-derived DNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2287.