STAT3 and head and neck squamous cell carcinoma: Not surprisingly, activated STAT3 alone can also increase PD-L1 expression by directly acting on the promoter of PD-L1 in HNSCC and lymphoma cells (267, 274, 275), and STAT3 silencing leads to the downregulation of PD-L1 in ALK-negative ALCL cells and KRAS-mutant NSCLC cells (267, 271).