CYTOKINE-INDUCED NITRIC-OXIDE FORMATION IN NORMAL BUT NOT IN NEOPLASTIC MURINE LUNG EPITHELIAL-CELL LINES

Cytomix, a mixture of interferon-gamma, tumor necrosis factor-alpha, a nd interleukin-1 beta, induces nitric oxide (NO) production in lung ep ithelial cell lines. It is not known whether neoplastic transformation alters a cell's ability to form NO in response to cytokines. The pres ent study investigated NO formation in two murine lines of immortalize d ''normal'' (nontumorigenic) lung epithelial cells of alveolar type I I origin, E10 and C10, and their sibling spontaneous transformants, E9 and A5. Nontumorigenic cells elaborated much more NO after cytomix ex posure than did their tumorigenic counterparts. NO production was prev ented by inhibiting protein synthesis and NO synthase and attenuated b y dexamethasone. Northern and Western blot analyses of inducible NO sy nthase (iNOS) demonstrated cytomix-induced induction of iNOS only in n ontumorigenic cells. The deficiency in NO production in tumorigenic ce lls was not associated with reduced iNOS mRNA stability or with differ ences in cytomix-induced nuclear factor-kappa B activation. Although c ytomix caused a greater production of NO in E10 cells than in E9 cells , the same treatment induced equivalent proliferation in both cell lin es. These results indicate a specific deficiency in cytokine-induced N O synthesis in transformed murine lung epithelial cells relative to th eir normal progenitor cells and provide a model for investigating iNOS regulation.