The airway epithelium and submucosal glands are appealing targets for gene therapy of pulmonary manifestations of CF because they express high levels of CFTR in the tracheobronchial tree (with relatively lower levels of expression found in the respiratory epithelial cells as compared to higher levels in the SMG), and they have been characterized as a potential location of airway stem cells [6]–[10]. This evidence concerns the gene CFTR and cystic fibrosis.