Immortalization of subpopulations of respiratory epithelial cells from transgenic mice bearing SV40 large T antigen.

Murine lung epithelial (MLE) cell lines were produced from lung tumors derived from transgenic mice bearing the viral oncogene, SV40 large T antigen, under transcriptional control of the promoter-enhancer region of the human surfactant protein C (SP-C) gene. Cells were selected on the basis of increased murine cystic fibrosis transmembrane conductance regulator (mCFTR) mRNA content and were dilution cloned to produce distinct immortalized epithelial cell lines. MLE-13a3 cell lines expressing high levels of mCFTR mRNA also expressed apolipoprotein J (apoJ) mRNA, a developmentally regulated glycoprotein expressed preferentially in fetal lung. SP-A, -B, and -C were not detected or were present at low levels in the MLE cells that contained abundant CFTR and apoJ mRNA. In contrast, MLE cells, cloned on the basis of abundant surfactant protein mRNAs, expressed apoJ and mCFTR mRNAs at low levels. Forskolin-stimulated short-circuit current, typical of CFTR-mediated chloride transport activity, was generated by monolayers of subclones of the MLE-13a3 cell lines. Tumor necrosis factor-alpha stimulated mCFTR mRNA, whereas dexamethasone, retinoic acid, and phorbol ester had no effect on the levels of mCFTR mRNA in MLE-13a3 cells.