CLDN1 and cystic fibrosis: Consistent with elevated TGF-β1 levels reported in CF airways (Xu et al., 2009; Harris et al., 2011), chronic exposure to this cytokine triggered a robust EMT response across all CFBE cell lines, characterized by a decrease of epithelial markers (E-cadherin, CK18, claudin-1) and increased N-cadherin expression.