Abstract 1489: Increased levels of systemic LPS-positive bacterial extracellular vesicles in cancer patients with chemotherapy-induced intestinal barrier dysfunction

Abstract

Abstract Bacterial extracellular vesicles (EV) are nanometer-sized membrane particles transporting nucleic acids, metabolites, proteins and endotoxins (lipopolysaccharide (LPS)). As such, bacterial EV that enter the systemic circulation may deliver and elicit a variety of immunological and metabolic responses in different organs including the brain. To date, the systemic presence and activity of bacterial EV in patients with intestinal barrier dysfunction have not been investigated. We combined size exclusion chromatography and density gradient (DG) centrifugation to fractionate plasma LPS in two dimensions to separate bacterial EV-associated LPS from other LPS products. We evaluated plasma from healthy donors asymptomatic of intestinal barrier dysfunction versus cancer patients with radiation- or chemotherapy (with or without gastrointestinal mucositis). We quantitatively measured bacterial EV-associated LPS and other LPS products by performing Limulus Amebocyte Lysate (LAL) and Toll-like receptor 4 (TLR4) reporter assays and qualitatively confirmed the results by immunoelectron microscopy. LAL analysis of DG fractions corresponding to the density of bacterial EV, demonstrated significantly increased LPS activity in patients diagnosed with therapy-induced gastrointestinal mucositis compared to respective controls. In accordance, we detected elevated amounts of microbial pattern recognition receptor (PRR) ligands by determining TLR4 agonistic activity. Immunoelectron microscopy confirmed bacterial EV-associated LPS. In conclusion, LPS-positive bacterial EV are present in plasma, and correlate with impaired barrier integrity in cancer therapy-induced intestinal mucositis. Further studies are needed to understand systemic functions of circulating bacterial EV in cancer patients and cancer therapy-induced conditions. Citation Format: Joeri Tulkens, Olivier De Wever, An Hendrix. Increased levels of systemic LPS-positive bacterial extracellular vesicles in cancer patients with chemotherapy-induced intestinal barrier dysfunction [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1489.