Enhancement of Anti-Leukemia Immunity by Leukemia–Derived Exosomes Via Downregulation of TGF-β1 Expression

Abstract

Background/Aims: Minimal residual leukemia cells (MRLs) are difficult to eradicate through traditional treatment and therefore remain to be a major threat to the long-term survival of leukemia patients. Tumor-derived exosomes (TEXs), which carry tumor associated antigens (TAA), may be a potential cell-free tumor vaccine for the specific eradication of MRLs. However, TEXs are intended to be less immunogenic due to exosomal TGF-β1. To further optimize the efficacy of TEX-based vaccines, we investigated whether exosomes from TGF-β1 silenced leukemia cells (LEX_TGF-β1si) had an increased potential to induce a specific antitumor effect compared with non-modified exosomes. Methods: Exosomal TGF-β1 was downregulated via lentiviral shRNA silencing of TGF-β1 in leukemia cells. The characteristics of LEX_TGF-β1si were determined via electron microscopy, western blot analysis, and flow cytometry. The antitumor effect of LEX_TGF-β1si was evaluated by detecting the properties of LEX_TGF-β1si-pulsed dendritic cells (DCs), CD4⁺ T-cell proliferation, Th1 cytokine secretion, specific CTL activity, and NK cell function. Moreover, to verify the superiority of LEX_TGF-β1si immunization, LEX_TGF-β1si was subcutaneously injected into DBA/2 mice: either followed by tumor challenge or tumor bearing. Results: The lentiviral shRNA silencing of TGF-β1 in parental leukemia cells successfully downregulated the TGF-β1 level in leukemia cell derived exosomes (LEX). LEX_TGF-β1si was uptaken by DCs and was more potent in promoting DC function by upregulating the surface expression of costimulatory factors and MHC class II molecules, while inducing the secretion of IL-12p70 and TNF-α. Furthermore, immunization with LEX_TGF-β1si facilitated CD4⁺ T-cell proliferation and Th1 cytokine secretion, and stimulated stronger specific cytotoxic lymphocyte (CTL) response and nature killer (NK) cell cytotoxicity more efficiently compared to non-modified LEX. In mice models, immunization with LEX_TGF-β1si resulted in a more potent capability to inhibit tumor growth and to prolong survival, suggesting that LEX_TGF-β1si was more effective in both protective and therapeutic antitumor tests than non-modified LEX. Conclusions: These data suggested that down-regulation of exosomal TGF-β1 effectively induced potent anti-tumor immunity. Our strategy of optimizing exosome vaccine may have promising potential for leukemia immunotherapy.

Adipocyte-Derived Exosomes Carrying Sonic Hedgehog Mediate M1 Macrophage Polarization-Induced Insulin Resistance via Ptch and PI3K Pathways

“…Exosomes are endosome-derived vesicles with a diameter of 30~100 nm [9] that are widely involved in tissue repair [10,11] and the inflammatory reaction [12,13]. Carrying signalling molecules [14,15], exosomes have been accepted as markers of disease [16,17] or information vectors [18].…”

CD8+ T�cells stimulated by exosomes derived from RenCa cells mediate specific immune responses through the FasL/Fas signaling pathway and, combined with GM‑CSF and IL‑12, enhance the anti‑renal cortical adenocarcinoma effect

“…TEXs are not only involved in establishing a favorable microenvironment surrounding the tumor but also induce a comprehensive alteration of the immune system (27,28). A full understanding of TEX immunization includes the observation that TEXs are a source of shared TAA and stimulatory molecules for the innate immune response, which can induce T cell-dependent immunity in mice or human tumor models under some conditions (8)(9)(10)(11)(16)(17)(18). This property makes TEXs novel potential vaccines for the treatment of tumors.…”

“…As expected, RDE antigen-specific splenic CD8 + T cells displayed stronger cytotoxicity for the autologous tumor cells than the other types of tumor cells at any E/T ratio. In vitro experiments have shown that TEXs may need to rely on host DCs for the induction of an immune response (8)(9)(10)(11)(12)(13)(14); however, TEXs can be taken up by CD8 + T cells, although a lack of DC participation was reported in some experiments, and TEXs can directly induce specific killing activity of CD8 + T cells via exosomal MHC molecules (35). Notably, we observed a dramatic phenomenon in which RDE-stimulated CD8 + T cells displayed a slightly weaker lethality for CT26 cells and 4T1 cells.…”

“…Exosomes, especially tumor-derived exosomes (TEXs), which are membrane-bound extracellular vesicles 30-100 nm in size secreted by all tumor cells (3), have attracted considerable attention as potential tools for diagnosing cancer and delivering therapeutic anti-cancer drugs (4,5). However, some studies have shown that TEXs alone are less efficient in promoting T cell activation, and may even induce T cell apoptosis; moreover, tumor progression is enhanced and immune escape is promoted due to the expression of immunosuppressive mediators, such as FasL, TNF-associated apoptosis inducing ligand (TRAIL) (6), programmed death-ligand 1 (PD-L1) (7), transforming growth factor-β (TGF-β) (8)(9)(10)(11) and HSP72 (12). TEXs are highly enriched in tumor-associated antigens (TAAs) and a series of immune-associated proteins involved in antigen presentation, such as major histocompatibility complex (MHC) molecules (13), inducible co-stimulatory molecules (ICOS) (14) and heat shock proteins (HSP) (15).…”

Exosome: From leukemia progression to a novel therapeutic approach in leukemia treatment

“…Therefore, in order to have efficient vaccination based on TDEs, the TDEs-derived TGF-β1 should be counteracted. 32 It would be a novel exosomes-based tumor vaccination. Moreover, utilizing exosomes can be a helpful strategy to eliminate minimal residual diseases (MRDs).…”