Thus, since these cell lines are hardly comparable to each other due to different CFTR expression levels and to the diverse genetic background, further studies are needed to optimize culture conditions (i.e, passages) and treatment with CFTR agonists/inhibitors as well as to use wise pairs of non-CF/CF cells, as in the case of isogenic CFTR-deficient cells. This evidence concerns the gene CFTR and cystic fibrosis.