Objective: Serum samples from patients with head and neck squamous cell carcinoma (HNSCC) contain 50- to 100-nm membranous microvesicles (MV), which induce apoptosis of activated T cells. Our objective was to study the molecular profile and tumor origin of these MVs.
Design: We isolated MVs by exclusion chromatography and ultracentrifugation from serum samples of 20 patients with HNSCC, 20 healthy donors, and supernatants of tumor cell lines. Western blot analyses were performed with antibodies to MAGE 3/6, FasL, MHC classes I and II molecules, and other antigens. The MVs were tested in JAM (DNA fragmentation); caspase activation and CFSE proliferation assays were performed with activated T cells. The MVs released by tumor cells were visualized by electron microscopy and imaging. The MVs in MAGE 3/6-positive tumor supernatants and paired serum samples were compared, as were MVs derived from tumor or dendritic cells.