AKT1 and head and neck squamous cell carcinoma: Adding physiologically relevant concentrations of 4-(methylnitrosamino)-1-(3-pyridyl)-1- 1butanone (NNK), a major tobacco carcinogen, to the normal head and neck epithelial cells and HNSCC cell lines, rapidly and constitutively activated AKT through phosphorylation in a dose- and time-dependent manner.