Small extracellular vesicles from the plasma of head and neck cancer patients induce dysfunctional T cell phenotypes.

BACKGROUND: Head and neck cancer (HNC) is highly immunosuppressive. Despite advances with immune checkpoint (IC) inhibitors, many HNC patients fail to respond. Tumour-derived small extracellular vesicles (sEVs) may contribute to immune evasion and therapy resistance, possibly by altering T-cell phenotypes. METHOD: Plasma sEVs were isolated from HNC patient samples and controls via size-exclusion chromatography. The plasma sEVs were characterised and analysed for their effects on CD4⁺ and CD8⁺ T-cell function, IC levels and gene expression. RESULTS: HNC patient-derived sEVs inhibit CD4+ and CD8+ T-cell function and promote CD8+ T-cell apoptosis, correlating with disease progression. Plasma sEVs can enhance the conversion of ATP to AMP and modulate the expression of ectonucleotidases. IC profiling revealed complex alterations, with CD4⁺ T cells showing increased TIGIT and CTLA-4 but decreased BTLA, PD-1, and LAG-3 expression, whereas CD8⁺ T cells showed a downregulation of both inhibitory and stimulatory ICs. PD-1 blockade did not completely prevent sEV-mediated T-cell suppression. CONCLUSIONS: Our findings suggest that plasma sEVs contribute to systemic immune modulation in HNC by inducing dysfunctional T-cell phenotypes. The ability of plasma-derived sEVs to modulate IC expression on T cells underscores the need for further investigation into their relevance for immunotherapeutic strategies in HNC.