Enhanced induction of dendritic cell maturation and HLA-A*0201-restricted CEA-specific CD8+ CTL response by exosomes derived from IL-18 gene-modified CEA-positive tumor cells

Abstract

Dendritic cells (DC)-derived or tumor-derived exosomes are a population of nanometer sized membrane vesicles that can induce specific anti-tumor immunity. However, the immunogenic potential and efficiency of exosomes-based tumor vaccine are not satisfactory enough to achieve a curative effect in clinical trials. In this article we investigated whether IL-18 genetic modification of tumor cells can increase the efficacy of exosomes derived from IL-18 gene-modified tumor cells. We transfected carcinoembryonic antigen (CEA)-expressing tumor cells with a recombinant adenovirus encoding human IL-18 (AdhIL-18) and prepared the exosomes, Exo/IL-18, from IL-18 gene-modified tumor cells. We found that Exo/IL-18 naturally contain CEA and bioactive IL-18. Moreover, Exo-IL-18 are potent in chemoattracting DC and T cells, enhancing the proliferation and Th1 cytokine release of PBMC, and promoting the phenotypic and functional maturation of DC. Furthermore, Exo/IL-18-pulsed DC are quite potent to induce HLA-A*0201-restricted, CEA-specific CD8(+) CTL from the PBMC of HLA-A*0201 CEA(+) cancer patients in vitro. In almost all of these experiments, Exo/IL-18 show more potent functions than the conventionally prepared exosomes derived from parent tumor cells without IL-18 gene modification. Our findings suggest that Exo/IL-18 has more potent capability to induce specific anti-tumor immunity, and our strategy of IL-18 modification of exosomes is a feasible approach to develop exosomes-based tumor vaccines.

The exosomes in tumor immunity

“…For example, we extracted exosomes from tumor cells genetically modified with cytokine genes (IL-2 and IL-18). 82,83 These exosomes were found to induce DC maturation and CTL responses efficiently. Exosomes from Rab27a-overexpressing lung cancer cells and OVAexpressing EG7 elicited efficient antitumor immune responses.…”

Heat Shock Protein 70, Released from Heat-Stressed Tumor Cells, Initiates Antitumor Immunity by Inducing Tumor Cell Chemokine Production and Activating Dendritic Cells via TLR4 Pathway

“…To evaluate the functional status of tumor-infiltrating T cells, CD3 ϩ cells isolated from TIMC using immunomagnetic beads were cultured in vitro and stimulated with 2 g/ml anti-CD3 and anti-CD28 mAb (BD Pharmingen) and then examined for the proliferation and cytokine production capacity as described previously (18,19).…”

“…Every 2 days, 0.5 ml of supernatant was replaced with fresh medium. Seven days later, functions of stimulated CD8 ϩ T cells were evaluated by IFN-␥ release assay and cytotoxicity assay as described previously (18,19). To examine 3LL-specific CTL induction, we prepared BMDC from normal wild-type mice after in vitro cultured for 5 days, matured them with 100 ng/ml LPS stimulation for 48 h, pulsed them with 50 g/ml synthetic MHC-I-restricted peptides MUT1 (FEYNYAQL, high affinity for H-2K b ) and OVA (257-264, SIINFEKL, H-2K b ) at the final 1 h (20,21), and irradiated (5000 rad) them.…”

“…Forty-eight hours later, the SN were tested for the level of IFN-␥ by ELISA. Cytotoxicity assays were performed using standard 4-h 51 Cr release assay against labeled target cells as described (14,19). Targets for CTL activity were mature DC pulsed with MUT1 or OVA peptides for 1 h.…”

Therapeutic and diagnostic applications of extracellular vesicles

“…This can be stimulated by combining tumor-derived EVs with synthetic adjuvants [200] or using EVs derived from (genetically) modified tumor cells to enhance the presence of adjuvant-like components (e.g. heat treatment to enhance hsp70 in tumor-derived EVs [201] or genetically engineer tumor cells to release IL18 [202] or IL12 [203] in EVs). It appears that for both strategies of EV-mediated anticancer vaccination, vesicles have to be modified to enhance their immune stimulatory effect.…”