TGFB1 and cystic fibrosis: Examples include the plasminogen activator inhibitor 1 (PAI-1, SERPINE1), which is a pivotal pro-fibrotic YAP1-TEAD4 transcriptional target (53, 54), is increased in CF lungs and primary airway epithelial cells in conjunction with increased TGFβ signaling (49, 50).