Dual effect of DLBCL-derived EXOs in lymphoma to improve DC vaccine efficacy in vitro while favor tumorgenesis in vivo.

BACKGROUND: Exosomes derived from tumor cells (TEXs) are involved in both immune suppression, angiogenesis, metastasis and anticancer stimulatory, but the biological characteristics and role of diffuse large B cell lymphoma (DLBCL)-derived exosomes have been less investigated.

METHODS: Exosomes (EXOs) were isolated from OCI-LY3, SU-DHL-16, and Raji cells and biological characteristics of EXOs were investigated using electron microscopy, flow cytometry analysis, and Western blot analysis. The protein expression of EXOs was determined by an antibody array. Next, the communication between EXOs and lymphoma cell, stromal cell, dendritic cells (DCs), and T cells was evaluated. Finally, effect of DLBCL TEXs on tumor growth in vivo was investigated.

RESULTS: We demonstrated that EXOs derived from DLBCL cell lines displayed malignancy molecules such as c-Myc, Bcl-2, Mcl-1, CD19, and CD20. There was a different protein expression pattern between DLBCL TEXs and Burkitt lymphoma TEXs. DLBCL TEXs were easily captured by DCs and lymphoma cells, and mainly acted as an immunosuppressive mediator, evidenced by induction of apoptosis and upregulation of PD-1 in T cells. Furthermore, the TEXs stimulated not only cell proliferation, migration of stromal cells but also angiogenesis. As a result, the TEXs promoted tumor growth in vivo. On other hand, DLBCL TEXs did not induce apoptosis of DCs. After pulsed with the TEXs, DCs could stimulate clonal expansion of T cells, increase the secretion of IL-6 and TNFα, and decrease the production of immunosuppressive cytokine IL-4 and IL-10. The T cells from tumor bearing mice immunized by TEX were shown to possess superior antilymphoma potency relative to immunization of tumor lysates.

CONCLUSIONS: This study provides the framework for novel immunotherapies targeting TEXs in DLBCL.