Introduction

Head and neck squamous cell carcinoma (HNSCC) ranks as the seventh most common cancer worldwide. Exosomes play a key role in the progression of tumors including HNSCC. This study investigated the role of exosomes derived from the HNSCC cell line (UD5), with a focus on characterizing their surface markers and assessing their immunomodulatory potential on natural killer (NK) cells

Methods

Cell surface markers were determined on UD5 tumor cells by flow cytometry and extracellular vesicles were isolated from cell culture supernatants. Size and morphology were measured by dynamic light scattering and transmission electron microscopy, and typical exosomal surface markers were determined by flow cytometry. The binding affinity of Hsp70-positive exosomes to cmHsp70.1 mAb was assessed by microscale thermophoresis. The impact of exosomes on the cytotoxic activity of NK cells against UD5 cells was investigated in cell death assays.

Results

UD5 cells express immunosuppressive ligands for NK cells such as PD-L1 and HLA-E. Extracellular vesicles of UD5 cells present typical exosomal markers (CD9, CD63, CD81, Hsp70), PD-L1 and HLA-E, show a uniform size distribution of around 100 nm and bind the cmHsp70.1 mAb with a high affinity. A co-incubation of the exosomes with NK cells results in a down-regulation of the activatory receptor NKG2D.

Discussion

We characterized extracellular vesicles derived from the supernatant of the HNSCC cell line UD5 as exosomes, showed a phenotypical characterization of their surface markers and provided evidence for an immunosuppressive activity of tumor cell-derived exosomes to NK cells. Our findings provide valuable insights into the interaction of exosomes with NK cells and their potential to modulate anti-cancer immune responses.

The authors declare that there is no conflict of interest.