Stabilization of Slug by NF-κB is Essential for TNF-α -Induced Migration and Epithelial-Mesenchymal Transition in Head and Neck Squamous Cell Carcinoma Cells

BACKGROUND/AIMS: Slug protein, a transcription factor for the induction of epithelial-mesenchymal transition (EMT) and cancer cell invasion and metastasis, is frequently upregulated in human epithelial cancers. However, mutation of this gene in cancer is rare, and the mechanism of its dysregulation remains unknown, especially in head and neck squamous cell carcinoma (HNSCC). METHODS: We examined the role of TNF-α in the stabilization of Slug by immunoprecipitation-westernblot analysis. Migration of HNSCC cells with or without knockdown of Slug gene expression was assayed by a wound healing assay. Immunohistochemical staining analysis was used to measurement Slug levels in both normal and HNSCC tumor tissues. RESULTS: The inflammatory cytokine TNF-α stabilized Slug protein by inhibiting its ubiquitination through the NF-κB pathway. Inhibition of NF-κB or knockdown of p65 abrogated the TNF-α-induced stabilization of Slug. Knockdown of Slug expression inhibited cancer cell migration and EMT characteristics induced by TNF-α. Moreover, increased levels of Slug were found to correlate with lymph node metastasis and predict poor prognosis in patients with HNSCC. CONCLUSIONS: NF-κB-mediated stabilization of Slug underlies the inflammation-induced EMT and metastasis in HNSCC, which may serve as a therapeutic target for metastatic HNSCC.