The functional links we identified between β-catenin signalling, E-cadherin inhibition via Twist, Slug and Snail, and airway basal cell growth and differentiation may explain how canonical Wnt signalling pathway components become over-expressed in squamous cell carcinomas, despite a paucity of identified β-catenin mutations in this disease [47]. The gene discussed is TWIST1; the disease is squamous cell carcinoma.