PTEN and head and neck squamous cell carcinoma: Due to the capability of increasing cell proliferation and invasion and reducing apoptosis by targeting the 3’-UTR of the genes tropomyosin 1 (TPM1), phosphatase and tensin homolog (PTEN), cyclin dependent kinase 2 associated protein 1 (CDK2AP1), reversion inducing cysteine rich protein with kazal motifs (RECK), and Clusterin (CLU) [9–12], upregulation of miR-21 has been associated with resistance to the favoring HNSCC, ovarian cancer, oral squamous cell cancer, gastric malignancy and non-small cell lung cancer (NSCLC) development and patients’ poor prognosis [13].