Purpose <p>P-cadherin (CDH3) is a transmembrane protein that plays a crucial role in maintaining the structural integrity of epithelial tissue and homeostasis. Its role in carcinogenesis remains a subject of debate, as its behavior can vary depending on the molecular context and the specific tumor cell model under study. In this study, we explored the role of P-cadherin in head and neck squamous cell carcinoma (HNSCC) and the mechanisms underlying its function.</p> Methods <p>We analyzed P-cadherin expression in HNSCC patients using The Cancer Genome Atlas (TCGA), The Chungnam National University Hospital (CNUH) cohort and Gene Expression Omnibus (GEO) database. For in vitro functional analysis, we conducted proliferation, migration, invasion, and western blot assays after either suppressing or overexpressing P-cadherin. For in vivo functional analysis, we utilized mouse xenograft models.</p> Results <p>P-cadherin was significantly overexpressed in tumor samples compared to normal samples in the TCGA-HNSCC and CNUH-HNSCC cohorts. P-cadherin knockdown resulted in decreased proliferation, migration, and invasion compared to control cells, while P-cadherin overexpression increased cell proliferation and migration in HNSCC cells. We discovered that c-Met functions as an upstream regulator of P-cadherin. Surprisingly, we found that P-cadherin knockdown increased the phosphorylation of c-Met and STAT3. Combining P-cadherin siRNA with the c-Met inhibitor SU11274 or c-Met siRNA resulted in a more effective reduction in HNSCC cell growth, both in vitro and in vivo, compared to either treatment alone.</p> Conclusion <p>Our study uncovered a previously unknown aspect of P-cadherin-mediated c-Met regulation. The enhanced activation of c-Met/STAT3 following P-cadherin inhibition could be responsible for the survival of resistant tumor cells. Therefore, dual inhibition of P-cadherin and c-Met may be an effective approach for treating HNSCC.</p>