Characterization of Human NK Cell-Derived Exosomes: Role of DNAM1 Receptor in Exosome-Mediated Cytotoxicity against Tumor

Abstract

Despite the pivotal role of natural killer (NK) cells in defenses against tumors, their exploitation in cancer treatment is still limited due to their reduced ability to reaching tumor sites and the inhibitory effects of tumor microenvironment (TME) on their function. In this study, we have characterized the exosomes from IL2- or IL15-cultured human NK cells. Both cytokines induced comparable amounts of exosomes with similar cargo composition. Analysis of molecules contained within or exposed at the exosome surface, allowed the identification of molecules playing important roles in the NK cell function including IFN-γ, Lymphocyte Function-Associated Antigen (LFA-1), DNAX Accessory Molecule-1 (DNAM1) and Programmed Cell Death Protein (PD-1). Importantly, we show that DNAM1 is involved in exosome-mediated cytotoxicity as revealed by experiments using blocking antibodies to DNAM1 or DNAM1 ligands. In addition, antibody-mediated inhibition of exosome cytotoxicity results in a delay in target cell apoptosis. We also provide evidence that NK-exosomes may exert their cytolytic activity after short time interval and even at low concentrations. Regarding their possible use in immunotherapy, NK exosomes, detectable in peripheral blood, can diffuse into tissues and exert their cytolytic effect at tumor sites. This property offers a clue to integrate cancer treatments with NK exosomes.

Natural killer cell–derived extracellular vesicles in cancer therapy

“…Several studies have shown expression of NK cell receptors by NK‐EVs. Expression of FasL, DNAM‐1 and NKG2D are reported in several studies, while there is low and variable expression of NKp30, NKp46 and CD16 23,24,26 . Interestingly, NK‐EVs are also reported to contain the immune checkpoint B7‐H3/CD276 25 and CD47 27 .…”

“…EVs could also be taken up via phagocytosis or receptor‐independent endocytosis or micropinocytosis 22 . In vitro, NK‐EVs are shown to be internalized within haematological cell lines, 23,24 suggesting that NK‐EVs are endocytosed rather than fused with the target cell membranes.…”

“…NK‐EVs contain both FasL and perforin, and variable levels of granzyme A, granzyme B and granulysin 23‐25,28 . NK‐EVs are thus equipped for inducing both the extrinsic and intrinsic apoptotic pathways in cancer cells (Figure 1).…”

Exosome: A New Player in Translational Nanomedicine

“…Exosomes produced from NK cells and their apoptotic activity in tumor cells have also been studied. Exosomes obtained from IL-2-and IL-15-stimulated NK cells were detected in peripheral blood expressing the typical NK-related molecules CD16, CD69 and NKG2D which have high penetrance rates and a marked cytolytic effect on tumor sites [156]. NK-derived exosomes carrying the tumor suppressor microRNA (miR)-186 exhibit potent activity against neuroblastoma cell lines [157] and aggressive melanoma in vitro and in vivo [158], thus opening up the possibility of clinical applications using the antitumor activity of NK-derived exosomes [159].…”

Exosomal PD-L1 Derived From Osteosarcoma is Associated With Pulmonary Metastasis for Patients With Osteosarcoma

“…Inward budding of late endosomes develop into intracellular multivesicular endosomes and RNA, DNA, proteins and other small moleculars are encapsulated into exosomes during the formation of exosome [1,2]. Various types of cells such as immune cells, broblast and endothelial cells, release exosomes into the extracellular space and microenviroment, involving the tumor pathogenesis [3,4]. Recent studies reported that tumor cell-derived exosomes stimulated cancer and sarcoma cell growth, survival, metastasis, angiogenesis and chemotherapy resistance [5][6][7][8][9][10][11].…”