TGF-β1-silenced leukemia cell-derived exosomes target dendritic cells to induce potent anti-leukemic immunity in a...

Tumor-derived exosomes (TEX) can induce a specific antitumor immune response and have been developed as a promising tumor vaccine. Despite promising preclinical data, TEX exhibit relatively low efficacy and limited clinical benefit in clinical trials. In the present study, we investigated whether exosomes from the TGF-β1 silenced L1210 cells (LEX_TGF-β1si) can enhance the efficacy of DC-based vaccines. We silenced TGF-β1 in L1210 cells with a lentiviral shRNA vector and prepared the LEX_TGF-β1si. It was shown that LEX_TGF-β1si can significantly decrease TGF-β1 expression of dendritic cells (DC) and effectively promote their maturation and immune function. In addition, DC pulsed with LEX_TGF-β1si (DC_{LEX-TGF-β1si}) more effectively promoted CD4⁺ T cell proliferation in vitro and Th1 cytokine secretion and induced tumor-specific CTL response. This response was higher in potency compared to that noted by the other two formulations. Moreover, DC_{LEX-TGF-β1si} inhibited tumor growth more efficiently than other formulations did as the preventive or therapeutic tumor vaccine. Accordingly, these findings revealed that DC_{LEX-TGF-β1si} induced a more potent antigen-specific anti-leukemic immunity than DC pulsed with exosomes from non-manipulated L1210 cells. This indicated that the targeting of DC by LEX_TGF-β1si may be used as a promising approach for leukemia immunotherapy.