Cystic fibrosis—correct chloride conductance can cure cells



We have used retrovirus-mediated gene transfer to demonstrate complementation of the cystic fibrosis (CF) defect in vitro. Amphotropic retroviruses were used to transduce a functional cystic fibrosis transmembrane conductance regulator (CFTR) cDNA into CFPAC-1, a pancreatic adenocarcinoma cell line derived from a patient with CF that stably expresses the chloride transport abnormalities characteristic of CF. CFPAC-1 cells were exposed to control virus (PLJ) and CFTR-expressing virus (PLJ-CFTR); viral-transduced clones were isolated and subjected to molecular and physiologic analysis. RNA analysis detected a viralderived CFTR transcript in all of the PLJ-CFTR clones that contained unrearranged proviral sequences. Agents that increase intracellular cAMP stimulated 125I efflux in PLJ-CFTR clones but not PLJ clones. Whole-cell patch-clamp performed on three responding clones showed that the anion efflux responses were due to cAMP stimulation of Cl conductance. Our findings indicate the expression of the normal CFTR gene confers cAMP-dependent Cl channel regulation on CF epithelial cells.

The cystic fibrosis transmembrane conductance regulator (CFTR) was expressed in cultured cystic fibrosis airway epithelial cells and Cl channel activation assessed in single cells using a fluorescence microscopic assay and the patch-clamp technique. Expression of CFTR, but not of a mutant form of CFTR (ΔF508), corrected the Cl channel defect. Correction of the phenotypic defect demonstrates a causal relationship between mutations in the CFTR gene and defective Cl transport which is the hallmark of the disease.