Objectives/Hypothesis The presence of regional metastases in head and neck squamous cell carcinoma (HNSCC) patients is a common and adverse event associated with poor prognosis. Understanding the molecular mechanisms that mediate HNSCC metastasis may enable identification of novel therapeutic targets. E‐cadherin plays a key role in epithelial intercellular adhesion; its downregulation is a hallmark of the epithelial‐to‐mesenchymal transition (EMT) (an essential process during tumor progression); and it is associated with invasion, metastasis, and decreased survival. Inflammatory cytokines have been implicated in the progression of HNSCC. Herein, the mechanisms by which the inflammatory mediator, Interleukin‐1β (IL‐1β), might contribute to EMT in HNSCC is investigated. The pathways involved in E‐cadherin regulation in HNSCC had not previously been defined. It is hypothesized that 1) inflammatory mediators upregulate cyclooxygenase‐2/prostaglandin E2 (COX‐2/PGE2), which then in turn regulate E‐cadherin expression in HNSCC; and 2) PGE2 downregulates E‐cadherin via transcriptional repressors of E‐cadherin (such as Snail) in HNSCC. The outcome of the proposed research will allow us to define how resistance to epidermal growth factor receptor (EGFR)‐selective tyrosine kinase inhibitors is mediated and whether the benefits of combination therapy are due to the capacity of COX‐2 inhibitors to increase E‐cadherin expression and thus create a more sensitive target for EGFR TK inhibition. Study Design Basic science, molecular biology, animal model, immunohistochemistry. Methods We evaluated the effect of IL‐1β on the molecular events of EMT in surgical specimens and HNSCC cell lines. We examined the correlation with tumor histologic features, and a severely compromised immunodeficient (SCID) xenograft model was used to assess the effects in vivo. Results COX‐2‐dependent pathways contribute to the modulation of E‐cadherin expression in HNSCC. An inverse relationship between COX‐2 and E‐cadherin was demonstrated in situ by double immunohistochemical staining of human HNSCC tissue sections. Treatment of HNSCC cells with IL‐1β caused the downregulation of E‐cadherin expression and upregulation of COX‐2 expression. This effect was blocked in the presence of COX‐2 small hairpin RNA (shRNA). IL‐1β ‐treated HNSCC cell lines demonstrated a significant decrease in E‐cadherin messenger RNA (mRNA) and an increase in the mRNA expression of the transcriptional repressor Snail. IL‐1β exposure led to enhanced Snail binding at the chromatin level. ShRNA‐mediated knockdown of Snail interrupted the capacity of IL‐1β to downregulate E‐cadherin. Snail overexpression in normal oral keratinocytes and HNSCC cells is sufficient to drive EMT and confers resistance to erlotinib. In a SCID xenograft model, HNSCC Snail overexpressing cells demonstrated significantly increased primary and metastatic tumor burdens. Conclusions The inflammatory mediator IL‐1β modulates Snail and thereby regulates COX‐2‐dependent E‐cadherin expression in HNSCC. This is the first report indicating the role of Snail in the inflammation‐induced promotion of EMT in HNSCC. This newly defined pathway for transcriptional regulation of E‐cadherin in HNSCC has important implications for targeted chemoprevention and therapy. Level of Evidence N/A Laryngoscope, 125:S1–S11, 2015