Background: Cancer-induced immunosuppression is antigen-specific rather than systemic and the mechanisms for the antigen specificity are incompletely understood.,Here we explore the option that tumor-associated antigens (TAAs) may be transferred to antigen-presenting cells (APCs), together with immunosuppressive molecules, through cancer-derived small extracellular vesicles (sEVs), such as exosomes.,Stimulation of a suppressive phenotype in the very same APCs that take up TAAs may yield antigen-specific tolerance.,Methods: sEVs isolated from patient-derived or well-established melanoma cell lines were used to demonstrate the transfer of major histocompatibility complex (MHC) molecules to the surface of APCs.,The immunosuppressive influence of sEVs was assessed by flow cytometry analysis of activation markers, cytokine expression, and mixed lymphocyte reactions.,Results: MHC class I molecules were transferred from melanoma cells to the cell surface of APCs by sEVs.,Concomitantly, CD86 and CD40 co-stimulatory molecules were down-regulated and IL-6 production was strongly induced.,TGF-β transported by sEVs contributed to the promotion of a suppressive phenotype of APCs.,Conclusion: The presented results indicate the existence of a hitherto undescribed mechanism that offers an explanation for antigen-specific tolerance induction mediated by cancer-derived sEVs.
Local acidification of stroma is proposed to favour pre-metastatic niche formation but the mechanism of initiation is unclear.,We investigated whether Human Melanoma-derived exosomes (HMEX) could reprogram human adult dermal fibroblasts (HADF) and cause extracellular acidification.,HMEX were isolated from supernatants of six melanoma cell lines (3 BRAF V600E mutant cell lines and 3 BRAF wild-type cell lines) using ultracentrifugation or Size Exclusion Chromatography (SEC).,Rapid uptake of exosomes by HADF was demonstrated following 18 hours co-incubation.,Exposure of HDAF to HMEX leads to an increase in aerobic glycolysis and decrease in oxidative phosphorylation (OXPHOS) in HADF, consequently increasing extracellular acidification.,Using a novel immuno-biochip, exosomal miR-155 and miR-210 were detected in HMEX.,These miRNAs were present in HMEX from all six melanoma cell lines and were instrumental in promoting glycolysis and inhibiting OXPHOS in tumour cells.,Inhibition of miR-155 and miR-210 activity by transfection of miRNA inhibitors into HMEX reversed the exosome-induced metabolic reprogramming of HADF.,The data indicate that melanoma-derived exosomes modulate stromal cell metabolism and may contribute to the creation of a pre-metastatic niche that promotes the development of metastasis.