title: Immunosuppression in malignant melanoma induced by tumor-derived extracellular vesicles
creator: Fleming, Viktor
subject: ddc-570
subject: 570 Life sciences
description: The aim of this project was to investigate the role of tumor-derived extracellular vesicles (EV) in the induction of immunosuppression in malignant melanoma. Here, we focused on the effect of tumor-derived EV isolated from the Ret murine melanoma model (Ret) on bone marrow (BM)-derived immature myeloid cells (IMC). We demonstrated that IMC efficiently took up Ret-EV that resulted in the secretion of inflammatory molecules and upregulation of miRNA resembling an immunosuppressive phenotype. Furthermore, we found that Ret-EV upregulated the expression of PD-L1 on IMC. This PD-L1 expression was induced due the TLR signaling pathway, where TLR4 played a dominant role followed by TLR2 and TLR7. The TLR signaling led to the activation of NF-B, thereby inducing the transcription of PD-L1. Blocking the NF-B pathway diminished the Ret-EV-mediated PD-L1 upregulation on IMC. To test whether IMC becomes immunosuppressive upon the treatment with Ret-EV, we performed inhibition of T cell proliferation and IFN- secretion assays. Here, we demonstrated that IMC became immunosuppressive and converted into MDSC. The immunosuppressive activity of Ret-EV-treated IMC was mainly due to the induction of PD-L1. By blocking PD-L1 with neutralizing antibodies, we could almost completely abrogate the immunosuppressive properties of Ret-EV-treated IMC. Investigating the ligands for this TLR-dependent upregulation of PD-L1, we found that the inducible heat shock protein (HSP) 86 was the dominant ligand on Ret-EV, inducing TLR4 signaling in IMC upon Ret-EV treatment. Inhibition of all inducible HSP on EV by KNK-437 resulted in the reduction of the Ret-EV mediated conversion of IMC into MDSC. Furthermore, we stably knocked-down HSP86 on Ret cells. By co-culturing HSP86-deficient Ret cells with IMC, we could not observe a PD-L1 upregulation, whereas the scramble control showed a strong increase in PD-L1 expression. When using DMA to block EV secretion, the EV-mediated PD-L1 upregulation was strongly diminished. Finally, we observed an impaired tumor growth of HSP86-deficient Ret cells compared to wild type cells in vivo that was accompanied by reduced levels of MDSC expressing PD-L1 in the tumor microenvironment (TME).  Summary  VIII  Taken together, our findings demonstrate a critical role in converting IMC into MDSC for HSP86 on EV that could be a promising target for immunotherapy.
date: 2019
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/25844/1/PhD%20thesis%20Viktor%20Fleming.pdf
identifier: DOI:10.11588/heidok.00025844
identifier: urn:nbn:de:bsz:16-heidok-258445
identifier:   Fleming, Viktor  (2019) Immunosuppression in malignant melanoma induced by tumor-derived extracellular vesicles.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/25844/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng