Exosomes in HNSCC Plasma As Surrogate Markers of Tumour Progression and Immune Competence

Exosomes in plasma of head and neck squamous cell carcinoma (HNSCC) patients comprise subsets of vesicles derived from various cells. Recently, we separated CD3 from CD3 exosomes by immune capture. CD3 exosomes were largely tumour-derived (CD44v3 ). Both subsets carried immunosuppressive proteins and inhibited functions of human immune cells. The role of these subsets in immune cell reprogramming by the tumour was investigated by focusing on the adenosine pathway components. Spontaneous adenosine production by CD3 or CD3 exosomes was measured by mass spectrometry, as was the production of adenosine by CD4 CD39 regulatory T cells (T ) co-incubated with these exosomes. The highest level of CD39/CD73 ectoenzymes and of adenosine production was found in CD3 exosomes in patients with the stages III/IV HNSCCs). Also, the production of 5'-AMP and purines was significantly higher in T co-incubated with CD3 than CD3 exosomes. Consistently, CD26 and adenosine deaminase (ADA) levels were higher in CD3 than CD3 exosomes. ADA and CD26 levels in CD3 exosomes were significantly higher in patients with early (stages I/II) than advanced (stages III/IV) disease. HNSCC patients receiving and responding to photodynamic therapy had increased ADA levels in CD3 exosomes with no increase in CD3 exosomes. The opposite roles of CD3 ADA CD26 and CD3 CD44v3 adenosine-producing exosomes in early versus advanced HNSCC suggest that, like their parent cells, these exosomes serve as surrogates of immune suppression in cancer.