STAT3 and head and neck squamous cell carcinoma: The purpose of this study is to clarify whether constitutive stimulation of human hypopharyngeal primary cells (HHPC) and immortalized human hypopharyngeal keratinocytes (HHK) with acidic (pH 4.0), weakly acidic (pH 5.0) or neutral (pH 7.0) pepsin is capable of inducing transcriptional activation of anti-apoptotic genes, including bcl-2, cell signaling TNF-α, oncogenic EGFR, STAT3, wnt5α, Tp63 or altering the expression of cell cycle control-related Tp53 linked to HNSCC [18–32].