Exosomes of MF are cancer prone immune modulators

Introduction- Primary cutaneous T-cell lymphomas (CTCLs) are a heterogeneous group of non-Hodgkin lymphomas. Mycosis fungoides (MF) and Sézary syndrome are the most common CTCL. Cancer exosomes are endosome-derived nano-sized extra-cellular vesicles that create a favorable tumor microenvironment (TME). We previously showed that MF-exosomes promote cell motility and enriched with miR-155 and miR-1246. Herein, we aimed to explore the protein content of MF-exosomes and their involvement in drug resistance and the immune regulation.
Methods- Exosomes were isolated from CTCL cell lines,plasma of MF patients, and healthy individuals, bydifferential ultracentrifugation, validated by Nanosight and FACS. The exosomes were profiled by proteomicmass spectrometry, validated with FACS analysis. The delivery of exosomal proteins into MF-cell line and healthy PBMCs was analyzed by immunostaining of the recipient cells. Survival assay was done by MTT, apoptosis by FACS of PI+annexin-V, and polarization ofimmune cells by cyTOF and FACS.
Results- Proteomic analysis of MF-exosomes revealedenriched cargo of immune related and lymphoma related proteins such as OX40, GITR, CXCR4, CD44 and CD30. The uptake of those exosomal proteins was validated by their immunostaining in the recipient cells. MF-exosomes desensitize cells to doxorubicin in dependency on CXCR4. MF-exosomes reduced the viability of T cells, increased their apoptosis, and polarized them into T-regs. Applying cyTOF analysiswith 41 antibodies showed that MF-exosomes deliver inhibitory signal to different immune cell subsets by upregulating PDL-1, CTLA-4 and, CD47 in the target cells. Conclusions- MF-exosomes mediate chemoresistance, remodel immune cell activity and polarization towardsimmune suppression and evasion.