Exosomes: A new delivery system for tumor antigens in cancer immunotherapy

Abstract

Exosomes are small membrane vesicles that are released into the extracellular environment during fusion of multivesicular bodies with plasma membrane. Exosomes are secreted by various cell types including hematopoietic cells, normal epithelial cells and even some tumor cells. They are known to carry MHC class I, various costimulatory molecules and some tetraspanins. Recent studies have shown the potential of using native exosomes as immunologic stimulants. Here, we demonstrate a novel means of using exosomes engineered to express a specific tumor antigen to generate an immune response against tumors. We expressed a target tumor antigen, human MUC1 (hMUC1), in 2 MHC typedistinct mouse cell lines, CT26 and TA3HA. Analysis of exosomes purified from these cells revealed that exosomes contained the target MUC1 antigen on their surfaces as well as other welldescribed exosomal proteins, including Hsc70 and MHC class I molecules. In addition, both autologous and allogenic exosomes were able to stimulate the activation of immune cells and suppress hMUC1-expressing tumor growth in a MUC1-specific and doserelated manner. Therefore, these data suggest that exosomes can be engineered from tumor cell lines to deliver a target immunogen capable of inducing an effective immune response and that they may represent a new cell-free tumor vaccine. © 2004 Wiley-Liss, Inc. Key words: exosomes; membrane vesicles; hMUC1; Hsc70; cell-free tumor vaccine Exosomes were initially described as small membrane vesicles (40 -90 nm in diameter), which are released from reticulocytes in order to eliminate unnecessary proteins, such as transferrin receptor (TfR) or acetylcholine esterase, during the process of their final maturation into red blood cells. [1][2][3][4] These extracellular vesicles are also produced by various kinds of hematopoietic cells, including mast cells, platelets, T lymphocytes, B lymphocytes and dendritic cells (DCs), as well as by intestinal epithelial cells. [5][6][7][8][9][10][11][12][13] Exosomes are known to originate from the inward budding of limiting membrane of multivesicular bodies (MVBs), and these internal vesicles of MVBs are released into the extracellular space by fusion of MVBs with the plasma membrane. 14 Proteomic analysis of DC-or B-cell-derived exosomes revealed selective enrichment of a subset of cellular proteins, including antigen-presenting proteins such as MHC class I and II molecules, heat shock proteins (HSPs), targeting-related MFG-E8 and tetraspanins such as CD9, CD63, CD81 and CD82. [15][16][17][18] In addition, a recent study by Hegman et al. has demonstrated that exosomes secreted by human mesothelioma cells contain a discrete set of proteins associated with antigen presentation, signal transduction, migration and adhesion. 19 The function(s) of exosomes are not well defined but have been reflected by their protein composition and cellular origins. 14,20 Although exosomes are known to discard membrane proteins such as transferrin receptors in reticulocytes, several lines of studies have sug...

Introduction of theCIITAgene into tumor cells produces exosomes with enhanced anti-tumor effects

“…To alleviate the negative effects as well as to increase the anti-tumor effects, it is necessary to develop an innovative method for tumor-derived exosomes. Previously, we have reported improved anti-tumor effects of manipulated tumor-derived exosomes by enrichment with human tumor antigen MUC-1 and Hsp70 that efficiently suppressed tumor growth (Cho et al, 2005(Cho et al, , 2009). Therefore, tumor-derived exosomes-based immunotherapy needs to be modified to increase therapeutic efficacy and enhance immunogenicity.…”

“…Tumor-derived exosomes contain tumor-specific antigens and tumor peptide/ MHC class I complexes that can prime tumor-specific CTLs and can elicit a potent tumor-specific immune response (Wolfers et al, 2001). Malignant effusions accumulate exosomes bearing tumor antigens and antigenpresenting molecules that can generate anti-tumor T cell responses (Andre et al, 2002), and exosomes from different tumor cells showed that exosomes prohibited not only syngeneic but also allogeneic tumor growth (Andre et al, 2002;Cho et al, 2005). These studies provide a rationale that tumor-derived exosomes have the potential as an efficient cell-free therapeutic vaccine.…”

Mucin 1 enhances the tumor angiogenic response by activation of the AKT signaling pathway

“…Full-length human MUC1 (MUC1) expression using a retroviral construction was prepared, as described previously (Cho et al, 2005). Supernatants that contain MUC1 encoding retroviral particles were transduced into MDA-MB-231 and T47D human breast adenocarcinoma cell lines.…”

Novel Exosome-Targeted CD4+ T Cell Vaccine Counteracting CD4+25+ Regulatory T Cell-Mediated Immune Suppression and Stimulating Efficient Central Memory CD8+ CTL Responses

“…Zitvogel et al (3) first demonstrated vaccination of DC-derived EXO in eradication of tumors in animal models. Subsequently, EXO-based vaccines have been confirmed to stimulate strong CTL responses and induce antitumor immunity in different animal models (6,7). However, its therapeutic efficiency is still limited to only production of prophylactic immunity against tumors possibly due to lacking capacity of breaking immune tolerance (8).…”