Epigenomic alterations and gene expression profiles in respiratory epithelia exposed to cigarette smoke condensate

Oncogene. 2010 Jun 24;29(25):3650-64. doi: 10.1038/onc.2010.129. Epub 2010 May 3.

Abstract

Limited information is available regarding epigenomic events mediating initiation and progression of tobacco-induced lung cancers. In this study, we established an in vitro system to examine epigenomic effects of cigarette smoke in respiratory epithelia. Normal human small airway epithelial cells and cdk-4/hTERT-immortalized human bronchial epithelial cells (HBEC) were cultured in normal media with or without cigarette smoke condensate (CSC) for up to 9 months under potentially relevant exposure conditions. Western blot analysis showed that CSC mediated dose- and time-dependent diminution of H4K16Ac and H4K20Me3, while increasing relative levels of H3K27Me3; these histone alterations coincided with decreased DNA methyltransferase 1 (DNMT1) and increased DNMT3b expression. Pyrosequencing and quantitative RT-PCR experiments revealed time-dependent hypomethylation of D4Z4, NBL2, and LINE-1 repetitive DNA sequences; up-regulation of H19, IGF2, MAGE-A1, and MAGE-A3; activation of Wnt signaling; and hypermethylation of tumor suppressor genes such as RASSF1A and RAR-beta, which are frequently silenced in human lung cancers. Array-based DNA methylation profiling identified additional novel DNA methylation targets in soft-agar clones derived from CSC-exposed HBEC; a CSC gene expression signature was also identified in these cells. Progressive genomic hypomethylation and locoregional DNA hypermethylation induced by CSC coincided with a dramatic increase in soft-agar clonogenicity. Collectively, these data indicate that cigarette smoke induces 'cancer-associated' epigenomic alterations in cultured respiratory epithelia. This in vitro model may prove useful for delineating early epigenetic mechanisms regulating gene expression during pulmonary carcinogenesis.

MeSH terms

  • Bronchi / cytology
  • Bronchi / drug effects
  • Bronchi / metabolism
  • Bronchi / pathology
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • DNA Methylation / drug effects
  • Epigenesis, Genetic / drug effects*
  • Gene Expression Profiling*
  • Genomics*
  • Histones / metabolism
  • Humans
  • Lung Neoplasms / genetics
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / pathology
  • Oligonucleotide Array Sequence Analysis
  • Respiratory Mucosa / cytology
  • Respiratory Mucosa / drug effects*
  • Respiratory Mucosa / metabolism*
  • Respiratory Mucosa / pathology
  • Signal Transduction / drug effects
  • Smoke / adverse effects*
  • Smoking / adverse effects*
  • Tobacco / toxicity
  • Wnt Proteins / metabolism

Substances

  • Histones
  • Smoke
  • Wnt Proteins