Rapid Akt Activation by Nicotine and a Tobacco Carcinogen Modulates the Phenotype of Normal Human Airway Epithelial Cells

J Clin Invest. 2003 Jan;111(1):81-90. doi: 10.1172/JCI16147.

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 alpha(3)-/alpha(4)-containing or alpha(7)-containing nicotinic acetylcholine receptors, respectively. Activated Akt increased phosphorylation of downstream substrates such as GSK-3, p70(S6K), 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.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Apoptosis
  • Bronchi / drug effects*
  • Carcinogens*
  • Carrier Proteins / metabolism
  • Cell Death
  • Cell Survival
  • Cells, Cultured
  • DNA-Binding Proteins / metabolism
  • Enzyme Activation
  • Enzyme-Linked Immunosorbent Assay
  • Epithelial Cells / drug effects*
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors
  • Glycogen Synthase Kinase 3 / metabolism
  • Humans
  • Immunoblotting
  • Immunohistochemistry
  • Lung Neoplasms / metabolism
  • Nicotine*
  • Nitrosamines
  • Phenotype
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Protein Binding
  • Protein-Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Reverse Transcriptase Polymerase Chain Reaction
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • Time Factors
  • Tobacco*
  • Transcription Factors / metabolism
  • Ultraviolet Rays

Substances

  • Adaptor Proteins, Signal Transducing
  • Carcinogens
  • Carrier Proteins
  • DNA-Binding Proteins
  • EIF4EBP1 protein, human
  • FOXO1 protein, human
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors
  • Nitrosamines
  • Phosphoproteins
  • Proto-Oncogene Proteins
  • Transcription Factors
  • Nicotine
  • 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone
  • AKT1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Ribosomal Protein S6 Kinases, 70-kDa
  • Glycogen Synthase Kinase 3