ADO and head and neck squamous cell carcinoma: Thirdly, CD73 has been implicated in central aspects of tumor progression including the suppression of immune cells via ADO production, the regulation of proliferation, migration, angiogenesis, EMT, and a potential involvement in metastasis formation in various cancers including HNSCC [6, 10, 12, 18, 26, 29–33, 37, 52, 55, 56, 59, 60, 62, 63, 65].