EGF and head and neck squamous cell carcinoma: Epidermal growth factor (EGF) signaling is frequently overactivated in various carcinoma cells, including HNSCC cells; thus, we cultured HSC-3 cells under serum-free conditions, treated them with EGF to mimic tumor progression in vivo, and identified genes whose expression was significantly altered using DNA chip analysis followed by quantitative real-time polymerase chain reaction [7].