CFTR and cystic fibrosis: In summary, the results reported herein suggest that the inclusion of an S/MAR element to a canonical plasmid-based vector improves long term CFTR production and function in polarized epithelial cells opening the possibility that S/MAR elements could contribute to further improve more advanced CF gene therapy vectors such as the pGM169 plasmid or the retroviral rSIV.F/HN-hCEF-CFTR [15].