S100A8 and head and neck squamous cell carcinoma: In separate experiments, genes highly upregulated in HNSCC were further interrogated for their regulation by S100A8/A9 by ectopic overexpression in S100A8/A9-negative carcinoma cells and by knockdown of endogenous S100A8/A9 expression in HNSCC cells using short hairpin RNA (shRNA) interference.