GDNF and head and neck squamous cell carcinoma: Our findings were validated in an independent cohort confirming that the expression levels of FABP4, HMGA2, S100A10, GDNF, SLC7A,2 and GPR18 genes were associated with overall survival (OS) exclusively in HPV-positive HNSCC patients, while ST6GALNAC1 expression was associated with OS in HPV-negative HNSCC.