CFTR and cystic fibrosis: In particular, we employed the human lung adenocarcinoma Calu-3 cell line in which CFTR was stably silenced by a short hairpin (sh)RNA (SH3 cells), as previously described27, the well-established CF bronchial epithelial cell line CFBE41o- (parental), in which CFTR expression is almost undetectable (null), and cell lines derived from CFBE41o- cells over-expressing wild-type CFTR (CFBE41o- WT) or F508del-CFTR (CFBE41o- F508del).