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

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.

• Authors: F Liu, J K Killian, M Yang, R L Walker, J A Hong, M Zhang, S Davis, Y Zhang, M Hussain, S Xi, M Rao, P A Meltzer, D S Schrump
• Journal: Oncogene (Oncogene) Vol. 29 Issue 25 Pg. 3650-64 (Jun 24 2010) ISSN: 1476-5594 [Electronic] England
• PMID: 20440268 (Publication Type: Journal Article)

Chemical References

• Histones
• Smoke
• Wnt Proteins

Topics

• Bronchi (cytology, drug effects, metabolism, 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, metabolism, pathology)
• Oligonucleotide Array Sequence Analysis
• Respiratory Mucosa (cytology, drug effects, metabolism, pathology)
• Signal Transduction (drug effects)
• Smoke (adverse effects)
• Smoking (adverse effects)
• Tobacco (toxicity)
• Wnt Proteins (metabolism)