CD274 and head and neck squamous cell carcinoma: We further analyzed PD-L1 levels among seven HNSCC cell lines based on the RNA sequencing profiles of the GSE62027 cohort (three HPV-positive: 93VU147T, SCC047, SCC090; four HPV-negative: SCC61, HaCaT, SCC25, SQ20B) and found no distinct relationship between HPV status and PD-L1 expression in the HNSCC cell lines (Fig. 2c).