PDCD1 and head and neck squamous cell carcinoma: In the present research, we discovered that HNSCC with a low-risk score exhibited significantly upmodulated expression of immune checkpoint genes including CD8A, HAVCR2, LAG3, IFNG (IFNγ), GZMB, CTLA4, TNF, CD274, PRF1, GZMA, and PDCD1. PDCD1 (PD1), CD274 (PD-L1), and CTLA4 are three already known immune checkpoints, numerous studies have achieved great success in immunotherapy targeting PD1/PDL1 therapy in different solid tumors in the past decade60, and other immune checkpoint inhibitors have also made substantial progress.