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

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

miR-762 promotes HNSCC progression by targeting PHLPP2 and FOXO4. Therefore, miR-762 might be a potential diagnostic or therapeutic target for HNSCC.

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.

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.