Although checkpoint inhibitors (CPI) have recently extended the treatment options and improved clinical response of advanced stage head and neck squamous cell carcinoma (HNSCC), treatment success remains unpredictable. Programmed cell death ligandβ1 (PDβL1) is a key player in immunotherapy. Tumor cells, and exosomes derived therefrom, are carriers of PDβL1 and efficiently suppress immune responses. The aim of the present study was to analyze the influence of established therapies on β¦