Differential induction of early response genes by adrenomedullin and transforming growth factor-beta1 in human lung cancer cells.
ABSTRACT Adrenomedullin (AM) is a hypotensive polypeptide that has been shown to stimulate cyclic AMP and intracellular free Ca2+ agents that are known to induce expression of proto-oncogenes, in various cell types. Transforming growth factor-beta 1 (TGF-beta1) is a multifunctional polypeptide that regulates proliferation, differentiation and cell cycle progression in both normal and malignant epithelial cells. The diverse biological actions of AM and TGF-beta1 may be related to their capacities to initiate different genomic programs in target cells via the induction of expression of multiple genes including early response genes and proto-oncogenes. AM, TGF-beta1 and phorbol-12-myristate-13-acetate (PMA) exert both positive and negative effects on mitogenesis. The effects of AM, TGF-beta1 and PMA were examined in human non-small cell lung cancer (NSCLC) cells. AM caused an increase in its mRNA transcript that peaked by 6 hours and persisted to 24 hours. While expression of TGF-beta1 mRNA was not affected by AM in these cells, the mRNAs for TGF-beta1 and TGF-beta3 decreased by 3 hours. In contrast, TGF-beta1 had no effect on expression of AM mRNA. Interestingly, PMA caused an increase in AM and TGF-beta1 mRNAs in NSCLC cells. While both TGF-beta1 and PMA caused a transient increase in expression of the mRNAs for early response genes including c-fos, c-jun and egr-1 that peaked by 1 hour following treatment, the increase in expression of these mRNAs following treatment with AM peaked only after 3-6 hours. Western blotting analysis showed increases in the levels of c-jun protein following treatment with AM, TGF-beta1 and PMA. The increase in c-jun protein from treatment with AM occurred 10 hours after that from TGF-beta1 and PMA. Activator protein 1 (AP-1) DNA binding activity was also demonstrated to increase following treatment with AM, TGF-beta1 and PMA, with the increase in AP-1 DNA binding activity following AM treatment occurring 10 hours later than that from TGF-beta1 and PMA treatment. These data show that AM can regulate expression of its mRNA transcript in NSCLC cells. Our study suggests that NSCLC cells are important targets of AM and TGF-beta1 and that AM and TGF-beta1 may regulate activities in these malignant lung cells through differential induction of various early response genes.
Article: Early growth response gene 1-mediated apoptosis is essential for transforming growth factor beta1-induced pulmonary fibrosis.[show abstract] [hide abstract]
ABSTRACT: Fibrosis and apoptosis are juxtaposed in pulmonary disorders such as asthma and the interstitial diseases, and transforming growth factor (TGF)-beta(1) has been implicated in the pathogenesis of these responses. However, the in vivo effector functions of TGF-beta(1) in the lung and its roles in the pathogenesis of these responses are not completely understood. In addition, the relationships between apoptosis and other TGF-beta(1)-induced responses have not been defined. To address these issues, we targeted bioactive TGF-beta(1) to the murine lung using a novel externally regulatable, triple transgenic system. TGF-beta(1) produced a transient wave of epithelial apoptosis that was followed by mononuclear-rich inflammation, tissue fibrosis, myofibroblast and myocyte hyperplasia, and septal rupture with honeycombing. Studies of these mice highlighted the reversibility of this fibrotic response. They also demonstrated that a null mutation of early growth response gene (Egr)-1 or caspase inhibition blocked TGF-beta(1)-induced apoptosis. Interestingly, both interventions markedly ameliorated TGF-beta(1)-induced fibrosis and alveolar remodeling. These studies illustrate the complex effects of TGF-beta(1) in vivo and define the critical role of Egr-1 in the TGF-beta(1) phenotype. They also demonstrate that Egr-1-mediated apoptosis is a prerequisite for TGF-beta(1)-induced fibrosis and remodeling.Journal of Experimental Medicine 09/2004; 200(3):377-89. · 13.85 Impact Factor