CD8A and head and neck squamous cell carcinoma: Ma et al. reported that the expression levels of A2a in HNSCC were related to tumor volume, lymph node metastasis, recurrence, and preoperative adjuvant chemotherapy, and that the application of A2a receptor antagonists could enhance the antitumor effects of CD8+ T cells and reduce Treg infiltration, thus markedly impeding tumor growth.77