Furthermore, exosomes secreted from HNSCC are enriched with suppressive molecules such as inhibitory cytokines (IL-10 and TGF-β1), checkpoint receptor ligands (PD-L1), cyclooxygenase-2 (COX-2) and death receptor ligands (FasL), which can ultimately impair T and NK-cell function (Whiteside, 2016). This evidence concerns the gene PTGS2 and head and neck squamous cell carcinoma.