title: 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.affiliation: Thoracic Oncology Section, Surgery Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA.
authors.forename: F
authors.initials: F
authors.lastname: Liu
authors.forename: J K
authors.initials: JK
authors.lastname: Killian
authors.forename: M
authors.initials: M
authors.lastname: Yang
authors.forename: R L
authors.initials: RL
authors.lastname: Walker
authors.forename: J A
authors.initials: JA
authors.lastname: Hong
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: S
authors.initials: S
authors.lastname: Davis
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: M
authors.initials: M
authors.lastname: Hussain
authors.forename: S
authors.initials: S
authors.lastname: Xi
authors.forename: M
authors.initials: M
authors.lastname: Rao
authors.forename: P A
authors.initials: PA
authors.lastname: Meltzer
authors.forename: D S
authors.initials: DS
authors.lastname: Schrump
mesh_terms: D001980:Bronchi / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects; D044127:Epigenesis, Genetic / Q000187:drug effects*; D020869:Gene Expression Profiling; D023281:Genomics; D006657:Histones / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects; D012906:Smoke / Q000009:adverse effects*; D012907:Smoking / Q000009:adverse effects*; D051153:Wnt Proteins / Q000378:metabolism
chemical_list: D006657:Histones; D012906:Smoke; D051153:Wnt Proteins