Exosome in ascites can be a potential therapeutic target for gastric cancer with malignant ascites.

person Sujin Hyung Samgsung Medical Center, Seoul, South Korea info_outline Sujin Hyung, Jihoon Ko, Seung KIM, Won Ki Kang, Jeeyun Lee

Authors person Sujin Hyung Samgsung Medical Center, Seoul, South Korea info_outline Sujin Hyung, Jihoon Ko, Seung KIM, Won Ki Kang, Jeeyun Lee Organizations Samgsung Medical Center, Seoul, South Korea, Samsung Medical Center, Korea, CA, South Korea, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea, Division of Hematology-Oncology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea Abstract Disclosures Research Funding Other Background: Recently, exosomes widely distributed in body fluids, including blood, urine, saliva, and ascites, serve as an essential biomarker in cancers. Exosomes are considered as a cargo of potential oncogenic protein such as MET during cancer progression. Methods: Exosomes from the malignant ascites (exo Ascites ) of four patients with stage IV gastric cancers (GCs) were isolated by different serial centrifugation steps (300 g , 2000 g , 10,000 g , and 110,000 g at 4). After ultracentrifugation, nanoparticle tracking analysis, western blotting, and immunocytochemistry were performed for characterization of the exo Ascites . Results: In this study, we enrolled 4 patients with malignant ascites which needed to be drained for symptom control. In all 4 patients, we successfully isolated highly concentrated exosomes in 50 ml of ascites (range, 5510 8 – 260 10 8 exosomes/ml). (pt#1, 14010 8 particles/ml; pt#2, 138 10 8 , pt#3, 55.6 10 8 ; pt#4, 260 10 8 exosomes/ml). In twopatients with MET amplification (MET amp ) in tumor specimens, exo Ascites retrieved from the ascites harbored cMET protein in exosomes. In addition, the in-vitro cancer microenvironment model showed that tropism of exo Ascites harboring cMET oncogenic protein had the potential to induce cancer progression (EpCAM immunofluorescent intensity value; a 2.4-fold increase compared to control). In this model, the cancer invasiveness and angiogenesis were significantly enhanced by treatment with exo Ascites with over time. (2.4-(EpCAM immunofluorescent intensity) and 3.6-(CD31 immunofluorescent intensity) fold increase, respectively). Furthermore, the cancer invasiveness was substantially increased as the exosome concentration increased from 0, 10 1 , 10 3 , 10 5 , 10 7 exosome particles/ml. Cancer invasiveness measured by EpCAM immunofluorescent intensity was significantly decreased upon exo siMET treatment in MET amplified GC cells when compared to the control. Conclusions: For the first time, we demonstrated that exosomes from malignant ascites carry MET protein in their exosomes. Exosomes may be early mediators of cancer spread in GC.