β-Catenin Functions Mainly as an Adhesion Molecule in Patients with Squamous Cell Cancer of the Head and Neck

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Abstract
Background: β-catenin, depending on subcellular localization, plays a dual role in carcinogenesis: as a signaling factor (in the nucleus) and as an adhesion molecule (in cell membrane). In this study, we sought to determine the role of β-catenin in head and neck carcinogenesis. Methods: First, we studied the incidence of mutations of β-catenin in a cohort of 60 head and neck squamous cell cancers (HNSCC). We subsequently evaluated the protein expression levels of β-catenin in a cohort of oropharyngeal squamous cell cancer tissue microarray using a novel in situ method of quantitative protein analysis and correlated those with cyclin D1 levels and clinical and pathologic data. Results: The mean follow-up time for survivors was 45 months and for all patients was 35 months. We found no mutations in the cohort of 60 HNSCC. β-catenin displayed primarily membranous expression pattern. Patients with high tumor-node-metastasis stage were more likely to have high expression of β-catenin (P = 0.040). Patients with low β-catenin expression had a local recurrence rate of 79% compared with 29% for patients with high β-catenin tumors (P = 0.0021). Univariate Cox regression revealed a hazard ratio for low β-catenin tumors of 3.6 (P = 0.004). Kaplan-Meier analysis showed that patients with low β-catenin expressing tumors trended toward worse 5-year disease-free survival (P = 0.06). In multivariate analysis, only β-catenin expression status was an independent prognostic factor (P = 0.044) for local recurrence. Tumors with high β-catenin had low cyclin D1 and vice versa (P = 0.007). Conclusions: The absence of activating β-catenin mutations combined with the inverse correlation between β-catenin levels with cyclin D1 levels and outcome suggest that β-catenin mainly functions as an adhesion and not signaling molecule in HNSCC.