KRAS and head and neck squamous cell carcinoma: Importantly, a recent study demonstrated that PD-L1 expression in NSCLC cell lines is mediated by constitutively active mutant EGFR/KRAS-MAPK pathway (Akbay et al., 2013), whereas in the setting of HNSCC, overexpressed wild-type EGFR induced the expression of PD-L1 in a JAK2/STAT1 dependent manner.