CFTR and cystic fibrosis: Interestingly, a trend for higher proliferation (as assessed by Ki-67 staining) was found in polarized F508del-CFTR CFBE cells than in wt-CFTR-CFBE cells, while more striking results were observed for primary bronchial epithelial cells, since CF cells (with three different CFTR genotypes: F508del/F508del, R347P/711 +5 G > A and M1101K/1609delCA) exhibited 3-fold higher cell proliferation rates vs. control cells.