PTEN and neoplasm: Hypermethylation of tumor-related genes, such as cyclin-dependent kinase inhibitor 2A (CDKN2A), E-cadherin (CDH1), death-associated protein kinase (DAPK), phosphatase and tensin homolog (PTEN), and O6-methylguanine-DNA methyltransferase (MGMT), have been reported in HNC [8].