An Immunosuppressive Effect of Melanoma-derived Exosomes on NY-ESO-1 Antigen-specific Human CD8⁺ T Cells is Dependent on IL-10 and Independent of BRAF^V600E Mutation in Melanoma Cell Lines

ABSTRACT

Exosomes, including human melanoma-derived exosomes (HMEX), are known to suppress the function of immune effector cells, which for HMEX has been associated with the surface presence of the immune checkpoint ligand PD-L1. This study investigated the relationship between the BRAF mutational status of melanoma cells and the inhibition of secreted HMEX exosomes on antigen-specific human T cells. Exosomes were isolated from two melanoma cell lines, 2183-Her4 and 888-mel, which are genetically wild-type BRAF^WT and BRAF^V600E, respectively. HMEX were isolated using a modified, size-exclusion chromatography (SEC) method shown to reduce co-isolation of non-exosome-associated cytokines compared to ultracentrifugation isolation. The immunoinhibitory effect of the exosomes was tested in vitro on patient-derived NY-ESO-1-specific CD8⁺ T cells challenged with NY-ESO-1 antigen. HMEX from both cell lines inhibited the immune response of antigen-specific T cells comparably, as evidenced by the reduction of IFN-γ and TNF-α in NY-ESO-1 tetramer-positive cells. This inhibition could be partially reversed by the presence of anti-PD-L1 and anti-IL-10 antibodies. IL-10 has been demonstrated to be a critical pathway for sustaining enhanced tumorigenesis in BRAF^V600E mutant cells compared to BRAF^WT melanoma cells. Thus, we demonstrate that HMEX inhibit antigen-specific T cell responses independent of the BRAF mutational status of the parent cells. In addition, PD-L1 and IL-10 contribute to the HMEX-mediated immunosuppression of antigen-specific human T cells. The inhibitory capacity of exosomes should be taken into consideration when developing therapies that are reliant upon the potency of customized, antigen-specific effector T cells.

KEYWORDS:

• NY-ESO-1
• T cells
• exosomes
• IL-10
• PD-L1 and immunosuppression

Declaration of interest statement

All authors (S.S., J.M., M.Y.W., A.C., S.B., C.L.A., M.K., S.B., A.O., H.M., and M.S.E) declare no potential conflict of interest.

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Additional information

Funding

This work was supported by the National Cancer Institute [1R50CA211108, P30CA16056, S10OD018048]; RPCI-UPCI Ovarian Cancer SPORE [P50CA159981-01A1]; The Katherine Anne Gioia Endowed Chair in Cancer Medicine, Roswell Park Comprehensive Cancer Center.