PTEN and head and neck squamous cell carcinoma: PI3K/AKT/mTOR pathway activation and signal transduction leads to the inactivation of tumor suppressor phosphatase and tensin homolog gene (PTEN), mutation or overexpression of genes including PI3KCA, AKT, and MTOR, and activates various growth factor receptors (Courtney et al., 2010); common alterations in this pathway that are found in HNSCC include reduced expression of PTEN and amplification of AKT (Vander Broek et al., 2013).