CDKN1A and head and neck squamous cell carcinoma: Compared to virus-negative cases, virus-positive cases have fewer mutations of TP53, CDKN2A, and deletions of 9p21.3/CDKN2A-CDKN1A while exhibiting more mutations in RNA helicases DDX3X and EIF4A1. Furthermore, an analysis of clinical trials of PD-(L)1 inhibitors suggests an association of virus-positivity with higher treatment response rate, particularly evident in gastric cancer and head and neck squamous cell carcinoma.