Up-regulation of NGEF via the BRAF /ERK/AP1 pathway enhances invasion and migration abilities of BRAF-mutant thyroid cancer.

The BRAF mutation is one of the most common genetic alterations in thyroid tumors, and intrinsic feedback mechanisms have limited the clinical application of BRAF-specific inhibitors. This study aims to investigate the potential biological function of the downstream overexpressed molecule NGEF following the BRAF mutation and its regulatory mechanisms. By integrating data from the CEO database, TCGA database, and clinical samples, we found that NGEF is highly expressed in thyroid cancer and is positively correlated with tumor size, local lymph node metastasis, clinical stage, and disease-free survival. Intriguingly, analysis of TCGA data revealed that NGEF expression is significantly higher in BRAF-mutant thyroid cancers. Subsequent validation demonstrated that NGEF expression is markedly elevated in BRAF-mutant cancer cell lines and BRAF-engineered cellular models compared to normal cells and BRAF-negative cancer cells. Functional experiments, pathway enrichment analysis, and investigations into phenotype-associated biomarkers further revealed that NGEF promotes invasion and migration of BRAF-mutant thyroid cancer cells through the epithelial-mesenchymal transition (EMT) pathway. To explore the regulatory relationship between the BRAF mutation and NGEF expression, we used bioinformatics tools to predict transcription factors, conducted pathway inhibition experiments, and performed dual-luciferase reporter assays. These studies confirmed that BRAF regulates NGEF expression via the ERK/AP1 pathway. These findings suggest that NGEF enhances the invasive and migratory abilities of BRAF-mutant thyroid cancer cells through BRAF/ERK/AP1 upregulation and may serve as a potential therapeutic target for BRAF-mutant thyroid cancer cells.