Rapid Akt activation by nicotine and a tobacco carcinogen modulates the phenotype of normal human airway epithelial cells
Kip A. West ... Steven Belinsky, Phillip A. Dennis
Kip A. West ... Steven Belinsky, Phillip A. Dennis
Published January 1, 2003
Citation Information: J Clin Invest. 2003;111(1):81-90. doi:10.1172/JCI16147.
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Categories: Article Oncology

Rapid Akt activation by nicotine and a tobacco carcinogen modulates the phenotype of normal human airway epithelial cells

Abstract

Tobacco-related diseases such as lung cancer cause over 4.2 million deaths annually, with approximately 400,000 deaths per year occurring in the US. Genotoxic effects of tobacco components have been described, but effects on signaling pathways in normal cells have not been described. Here, we show activation of the serine/threonine kinase Akt in nonimmortalized human airway epithelial cells in vitro by two components of cigarette smoke, nicotine and the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Activation of Akt by nicotine or NNK occurred within minutes at concentrations achievable by smokers and depended upon α3-/α4-containing or α7-containing nicotinic acetylcholine receptors, respectively. Activated Akt increased phosphorylation of downstream substrates such as GSK-3, p70S6K, 4EBP-1, and FKHR. Treatment with nicotine or NNK attenuated apoptosis caused by etoposide, ultraviolet irradiation, or hydrogen peroxide and partially induced a transformed phenotype manifest as loss of contact inhibition and loss of dependence on exogenous growth factors or adherence to ECM. In vivo, active Akt was detected in airway epithelial cells and lung tumors from NNK-treated A/J mice, and in human lung cancers derived from smokers. Redundant Akt activation by nicotine and NNK could contribute to tobacco-related carcinogenesis by regulating two processes critical for tumorigenesis, cell growth and apoptosis.

Authors

Kip A. West, John Brognard, Amy S. Clark, Ilona R. Linnoila, Xiaowei Yang, Sandra M. Swain, Curtis Harris, Steven Belinsky, Phillip A. Dennis

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Detection of Akt phosphorylation in vivo. (a) Lung tissue, including epi...

Figure 6

Detection of Akt phosphorylation in vivo. (a) Lung tissue, including epithelial lining of airway lumen (Lu), from A/J mice given PBS orally was harvested and processed for immunohistochemistry with phosphospecific S473 antibodies as described. No staining is detectable. (b) Lung tumor (Tu) and epithelial lining of airway lumen (Lu) from A/J mice given NNK orally exhibit staining with phosphospecific S473 antibodies. (c) Quantification of phosphorylated Akt/total Akt in protein extracts derived from lung tissue from PBS- or NNK-injected mice. Quantification of immunoblots was performed using NIH Image software. (d) Phosphorylated Akt in a human lung adenocarcinoma derived from a smoker with a 48-pack-per-year smoking history.