NOS2 and head and neck squamous cell carcinoma: To verify the difference in NOS2, IL17REL, TMSB15A, and TUBB4A expression between non-HPV-related HNSCC and normal tonsil tissue, we performed qRT‒PCR to measure the expression of NOS2, IL17REL, TMSB15A, and TUBB4A at the transcriptional level and found that NOS2, IL17REL, TMSB15A, and TUBB4A expression in non-HPV-related HNSCC tissues was significantly lower than that in normal head and neck tissues (P value < 0.05, Fig. 3).