1-1-diethyl-2-hydroxy-2-nitrosohydrazine and Lung-Neoplasms

Many tumor cells or their secreted products suppress the function of tumor-infiltrating macrophages. Tumor cells often produce abundant transforming growth factor beta1 (TGF-beta1), which in addition to other immunosuppressive actions suppresses the inducible isoform of NO synthase. TGF-beta1 is secreted in a latent form, which consists of TGF-beta1 noncovalently associated with latency-associated peptide (LAP) and which can be activated efficiently by exposure to reactive oxygen species. Coculture of the human lung adenocarcinoma cell line A549 and ANA-1 macrophages activated with IFN-gamma plus lipopolysaccharide resulted in increased synthesis and activation of latent TGF-beta1 protein by both A549 and ANA-1 cells, whereas unstimulated cultures of either cell type alone expressed only latent TGF-beta1. We investigated whether exposure of tumor cells to NO influences the production, activation, or activity of TGF-beta1.A549 human lung adenocarcinoma cells exposed to the chemical NO donor diethylamine-NONOate showed increased immunoreactivity of cell-associated latent and active TGF-beta1 in a time- and dose-dependent fashion at 24-48 h after treatment. Exposure of latent TGF-beta1 to solution sources of NO neither led to recombinant latent TGF-beta1 activation nor modified recombinant TGF-beta1 activity. A novel mechanism was observed, however: treatment of recombinant LAP with NO resulted in its nitrosylation and interfered with its ability to neutralize active TGF-beta1. These results provide the first evidence that nitrosative stress influences the regulation of TGF-beta1 and raise the possibility that NO production may augment TGF-beta1 activity by modifying a naturally occurring neutralizing peptide.

Topics: Adenocarcinoma; Animals; Coculture Techniques; Enzyme Induction; Enzyme Precursors; Gene Expression Regulation, Neoplastic; Humans; Hydrazines; Image Processing, Computer-Assisted; Interferon-gamma; Lipopolysaccharides; Lung Neoplasms; Macrophage Activation; Macrophages; Mice; Neoplasm Proteins; Nitric Oxide; Nitric Oxide Donors; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Nitrogen Oxides; Oxidative Stress; Peptide Fragments; Protein Precursors; Protein Processing, Post-Translational; Proteins; Recombinant Fusion Proteins; Transforming Growth Factor beta; Transforming Growth Factor beta1