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  • Title: More efficient induction of HLA-A*0201-restricted and carcinoembryonic antigen (CEA)-specific CTL response by immunization with exosomes prepared from heat-stressed CEA-positive tumor cells.
    Author: Dai S, Wan T, Wang B, Zhou X, Xiu F, Chen T, Wu Y, Cao X.
    Journal: Clin Cancer Res; 2005 Oct 15; 11(20):7554-63. PubMed ID: 16243831.
    Abstract:
    PURPOSE: Tumor-derived exosomes are proposed as a new type of cancer vaccine. Heat shock proteins are potent Th1 adjuvant, and heat stress can induce heat shock protein and MHC-I expression in tumor cells, leading to the increased immunogenicity of tumor cells. To improve the immunogenicity of exosomes as cancer vaccine, we prepared exosomes from heat-stressed carcinoembryonic antigen (CEA)-positive tumor cells (CEA+/HS-Exo) and tested the efficacy of these exosomes in the induction of CEA-specific antitumor immunity. EXPERIMENTAL DESIGN: First, we identified the composition of CEA+/HS-Exo and observed their effects on human dendritic cell maturation. Then, we evaluated their ability to induce a CEA-specific immune response in vivo in HLA-A2.1/Kb transgenic mice and CEA-specific CTL response in vitro in HLA-A*0201+ healthy donors and HLA-A*0201+CEA+ cancer patients. RESULTS: CEA+/HS-Exo contained CEA and more heat shock protein 70 and MHC-I and significantly induced dendritic cell maturation. Immunization of HLA-A2.1/Kb transgenic mice with CEA+/HS-Exo was more efficient in priming a CEA-specific CTL, and the CTL showed antitumor effect when adoptively transferred to SW480-bearing nude mice. Moreover, in vitro incubation of lymphocytes from HLA-A*0201+ healthy donors and HLA-A*0201+CEA+ cancer patients with CEA+/HS-Exo-pulsed autologous dendritic cells induces HLA-A*0201-restricted and CEA-specific CTL response. CONCLUSIONS: Our results show that CEA+/HS-Exo has superior immunogenicity than CEA+/Exo in inducing CEA-specific CTL response and suggest that exosomes derived from heat-stressed tumor cells may be used as efficient vaccine for cancer immunotherapy.
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