Uptake Characterization of Tumor Cell-derived Exosomes by Natural Killer Cells

Background: Cancer is the leading cause of death in human disease and is a major public health problem around the world. Exosomes are a promising cancer biomarker and therapy target. Recent evidence demon-strate that tumor cells could inhibit natural killer (NK) cells’ immune surveillance function by releasing exo-somes into tumor microenvironment. The intercelluar uptake of tumor cell-derived exosomes by NK cells is vital for using these exosomes in tumor diagnose and therapy. We aimed to investigate the efficiency of NK cell uptake of tumor exosomes. Methods: Exosomes derived from different tumor cells, RAW264.7 cells and NK cells were labeled by fluo-rescent dye and co-cultured with NK cells. The uptake rates of NK cells were observed by fluorescence micro-scope and analyzed by flow cytometry. Results: NK cells could take up more exosomes from themselves and cell lines originating from bone marrow. Epithelial cell lines can take up more exosomes from epithelial cells. There was no significant difference in up-take efficiency between Jurkat cells and RAW264.7 cells by NK cells, indicating that maybe the origin other than species affects the efficiency of recipient cell uptake of exosomes. Different tumor cells derived exosomes had different uptake efficiency by NK cells. Conclusion: There is certain pattern of NK cells uptake tumor exosomes, which provide important insights on how tumors affect NK cells and develop appropriate countermeasures. In addition, it can be also helpful to select and design proper exosomes as a drug carrier in future.