We therefore propose, based on the results obtained in this study with CFBE41o− cells improved to mimic the PC pattern observed in freshly isolated CF cells (Fig. 4B), that UPR induction is not related to F508del-CFTR expression per se, but to secondary alterations in the cellular lipid composition (lipointoxication) related to hypoxia. Here, CFTR is linked to cystic fibrosis.