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 BRAFV600E Mutation in Melanoma Cell Lines.

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 BRAFWT and BRAFV600E, 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 BRAFV600E mutant cells compared to BRAFWT 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.

Annexin-A1 controls an ERK-RhoA-NFκB activation loop in breast cancer cells.

Wound healing is critical for normal development and pathological processes including cancer cell metastasis. MAPK, Rho-GTPases and NFκB are important regulators of wound healing, but mechanisms for their integration are incompletely understood. Annexin-A1 (ANXA1) is upregulated in invasive breast cancer cells resulting in constitutive activation of NFκB. We show here that silencing ANXA1 increases the formation of stress fibers and focal adhesions, which may inhibit wound healing. ANXA1 regulated wound healing is dependent on the activation of ERK1/2. ANXA1 increases the activation of RhoA, which is dependent on ERK activation. Furthermore, active RhoA is important in NF-κB activation, where constitutively active RhoA potentiates NFκB activation, while dominant negative RhoA inhibits NFκB activation in response to CXCL12 stimulation and active MEKK plasmids. These findings establish a central role for ANXA1 in the cell migration through the activation of NFκB, ERK1/2 and RhoA.

Annexin-A1 regulates TLR-mediated IFN-ß production through an interaction with TANK-binding kinase 1.

TLRs play a pivotal role in the recognition of bacteria and viruses. Members of the family recognize specific pathogen sequences to trigger both MyD88 and TRIF-dependent pathways to stimulate a plethora of cells. Aberrant activation of these pathways is known to play a critical role in the development of autoimmunity and cancer. However, how these pathways are entirely regulated is not fully understood. In these studies, we have identified Annexin-A1 (ANXA1) as a novel regulator of TLR-induced IFN-ß and CXCL10 production. We demonstrate that in the absence of ANXA1, mice produce significantly less IFN-ß and CXCL10, and macrophages and plasmacytoid dendritic cells have a deficiency in activation following polyinosinic:polycytidylic acid administration in vivo. Furthermore, a deficiency in activation is observed in macrophages after LPS and polyinosinic:polycytidylic acid in vitro. In keeping with these findings, overexpression of ANXA1 resulted in enhanced IFN-ß and IFN-stimulated responsive element promoter activity, whereas silencing of ANXA1 impaired TLR3- and TLR4-induced IFN-ß and IFN-stimulated responsive element activation. In addition, we show that the C terminus of ANXA1 directly associates with TANK-binding kinase 1 to regulate IFN regulatory factor 3 translocation and phosphorylation. Our findings demonstrate that ANXA1 plays an important role in TLR activation, leading to an augmentation in the type 1 IFN antiviral cytokine response.