miR-762 Promotes Malignant Development of Head and Neck Squamous Cell Carcinoma by Targeting PHLPP2 and FOXO4

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) is among the most common malignant tumors worldwide. This study, investigated the role of microRNA (miR)-762 in regulating HNSCC progression. MATERIALS AND METHODS: The expression levels of miR-762 in HNSCC tissues were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Statistical analyses were performed to investigate the association of miR-762 with clinicopathological features in patients with HNSCC. Cell proliferation and migration were examined by cell counting (CCK-8) and IncuCyte assays. Target genes of miR-762 were screened using bioinformatics tools and microarrays, and confirmed using a luciferase activity reporter assay, qRT-PCR and Western blot analysis. Recuse experiments were performed to detect whether target genes mediated the effects of miR-762 on HNSCC cells. The in vivo effects of miR-762 were verified using tumor xenografts. RESULTS: HNSCC clinical specimens showed high expression levels of miR-762, which positively correlated with tumor-node-metastasis (TNM) stage and poor prognosis of HNSCC. miR-762 overexpression promoted the proliferation and migration of HNSCC cells in vitro. In addition, overexpression of miR-762 upregulated the expression of phosphorylated AKT (p-AKT) and mesenchymal markers (N-cadherin and vimentin), but suppressed epithelial marker (E-cadherin) expression. miR-762 also promoted HNSCC tumor growth in vivo. PH domain and leucine-rich repeat protein phosphatase 2 (PHLPP2) and Forkhead box O4 (FOXO4) were direct target genes of miR-762. HNSCC tissues had low expression levels of PHLPP2 and FOXO4, showing a negative correlation with miR-762 expression. Moreover, silencing of PHLPP2 and FOXO4 mimicked the tumor-promotive effects of miR-762 on HNSCC cells. Notably, overexpression of PHLPP2 and FOXO4 abolished the pro-tumoral function of miR-762 on cell proliferation and migration. CONCLUSION: miR-762 promotes HNSCC progression by targeting PHLPP2 and FOXO4. Therefore, miR-762 might be a potential diagnostic or therapeutic target for HNSCC.