The expression of immune-checkpoints, including CD274, CTLA4, HAVCR2, LAG3, PDCD1, PDCD1LG2, TIGIT, and SIGLEC15 (Fig. 6A), were further investigated in the World Health Organization (WHO) grade II and III of HNSCC. Here, SIGLEC15 is linked to head and neck squamous cell carcinoma.