19 Effect of nasopharyngeal carcinoma-derived exosomes on human regulatory T cells

Abstract

Introduction Exosomes are nanovesicles found in large quantities in biological fluids and tumors of patients with nasopharyngeal carcinoma (NPC). These tumor exosomes play an important role in tumor progression due to their immunosuppressive properties. In addition, it has been reported that the frequency and suppressor functions of CD4 + CD25highFOXP3 + CD127low regulatory T cells (Treg) are also higher in NPC patients than healthy donors. Interactions between NPC-derived exosomes and Treg remain unknown. Here we investigated their ability to induce, expand, activate and recruit human Treg. Material and methods Treg recruitment by exosomes derived from NPC cell lines (C15/C17-Exo), exosomes isolated from NPC patients’ plasma (Patient-Exo), and CCL20 was tested in vitro using Boyden chamber assays and in vivo using a xenograft SCID mouse model ( N = 5), both in the presence and absence of anti-CCL20 monoclonal antibodies (mAb). Impact of these NPC exosomes (NPC-Exo) on Treg phenotype and function was determined using adapted assays (FACS, Q-PCR, ELISA and MLR). Experiments were performed in comparison with exosomes derived from plasma of healthy donors (HD-Exo). Results CCL20 allowed the intra-tumoral recruitment of human Treg. NPC-Exo also facilitated Treg recruitment (3.30 ± 0.34-fold increase, P P P = 0.0048) the expansion of human Treg, inducing the generation of Tim3Low Treg with increased expression of CD25 and FOXP3. Finally, NPC-Exo induced an overexpression of cell markers associated with Treg phenotype, properties and recruitment capacity. For example, GZMB mean fold change was 21.45 ± 1.75. These results were consistent with a stronger suppression of responder cells’ proliferation ( P Conclusion Interactions between NPC-Exo and Treg represent a newly defined mechanism that may be involved in regulating peripheral tolerance by tumors and in supporting immune evasion in human NPC.