These studies demonstrate the feasibility of transforming human airway epithelial cells while inducing only modest changes in function. Features central to the pathophysiology of cystic fibrosis, i.e., abnormal regulation of a chloride permeability in the apical cell membrane, appear to be preserved in the CF/T43 transformed cell line. This work indicates that additional cystic fibrosis and normal cell lines may be developed, as well as epithelial cell lines from other diseases of interest. In addition to SV40T gene, temperature-sensitive viral genes,41or genes driven by inducible promoters (e.g., glucocorticoids, heavy metals42) may produce cell lines in which proliferation or differentiation can be controlled. For example, the temperature-selective SV40A gene is expressed in cells cultured at the permissive (33°) temperature but is degraded at the nonpermissive (40°) temperature.41Thus, the transfected gene may induce proliferation to increase cell number, and then be suppressed to permit expression of a differentiated phenotype. Out strategy of initially selecting clones by G418 resistance and then selecting clones that develop functional tight junctions (and a transepithelial resistance) was useful in identifying a cell line with highly differentiated phenotypic properties. Cell lines that do not form transepithelial resistances may be valuable for studies that do not depend on cell polarization. Initial evidence suggests that some of the differentiated properties of CF/T43, i.e., formation of functional tight junctions and a transepithelial resistance, are lost at late passages. Although these properties may be a function of the culture medium constituents and the nature of the culture substrate, it is possible that the transforming gene caused further mutations that resulted in subclones that have increased growth rate but different phenotypic properties. The continuing expression of the CFTR messenger RNA in these late passage cells indicates that they will be an important tool for future CF research. © 1990, Elsevier Inc. All rights reserved.
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