Membrane‐bound HSP70‐engineered myeloma cell‐derived exosomes stimulate more efficient CD8⁺ CTL‐ and NK‐mediated antitumour immunity than exosomes released from heat‐shocked tumour cells expressing cytoplasmic HSP70

Abstract

Exosomes (EXO) derived from tumour cells have been used to stimulate antitumour immune responses, but only resulting in prophylatic immunity. Tumour-derived heat shock protein 70 (HSP70) molecules are molecular chaperones with a broad repertoire of tumour antigen peptides capable of stimulating dendritic cell (DC) maturation and T-cell immune responses. To enhance EXO-based antitumour immunity, we generated an engineered myeloma cell line J558HSP expressing endogenous P1A tumour antigen and transgenic form of membrane-bound HSP70 and heat-shocked J558HS expressing cytoplasmic HSP70, and purified EXOHSP and EXOHS from J558HSP and J558HS tumour cell culture supernatants by ultracentrifugation. We found that EXOHSP were able to more efficiently stimulate maturation of DCs with up-regulation of Iab, CD40, CD80 and inflammatory cytokines than EXOHS after overnight incubation of immature bone-marrow-derived DCs (5 × 106 cells) with EXO (100 μg), respectively. We also i.v. immunized BALB/c mice with EXO (30 μg/mouse) and assessed P1A-specific T-cell responses after immunization. We demonstrate that EXOHSP are able to stimulate type 1 CD4+ helper T (Th1) cell responses, and more efficient P1A-specific CD8+ cytotoxic T lymphocyte (CTL) responses and antitumour immunity than EXOHS. In addition, we further elucidate that EXOHSP-stimulated antitumour immunity is mediated by both P1A-specific CD8+ CTL and non-P1A-specific natural killer (NK) responses. Therefore, membrane-bound HSP70-expressing tumour cell-released EXO may represent a more effective EXO-based vaccine in induction of antitumour immunity.

Extracellular vesicles as a platform for membrane‐associated therapeutic protein delivery

“…For example, the addition of exosome membrane-bound HSP70 has been suggested as a method to maximize the vaccination effect of tumour cell-derived exosomes and induce a stronger immune response [111]. The engineering of exosomes for the surface expression of non-mutated tumour-associated antigen (TAA) has also been used to improve vaccine potency.…”

Exosomes as intercellular signalosomes and pharmacological effectors

“…The heat shock protein Hsp 70 is also involved in antigen presentation by enhancing peptide transfer on MHCs, and overexpression of Hsp 70 in tumor cells reverses the deleterious effects of tumor exosomes [105]. Thus the phenotypic modification of exosomes represents an alternative strategy to switch tumorogenic exosomes into anti-tumor ones.…”

TLR2-Mediated Expansion of MDSCs Is Dependent on the Source of Tumor Exosomes

“…In particular, tumor cells communicate with immune cells, leading to immune suppression. [1][2][3][4][5][6] One of the challenging issues is that the data generated from tumor cellderived exosomes released from in vitro cultured tumor cells may not represent the real effects caused by exosomes released from tumor cells being grown under immune pressure (a true physiological microenvironment). However, due to technical obstacles, it is difficult to isolate exosomes from solid tumor tissues.…”