title: Cigarette smoke induces epithelial to mesenchymal transition and increases the metastatic ability of breast cancer cells.
abstract: BACKGROUND
  Recent epidemiological studies demonstrate that both active and involuntary exposure to tobacco smoke increase the risk of breast cancer. Little is known, however, about the molecular mechanisms by which continuous, long term exposure to tobacco smoke contributes to breast carcinogenesis because most previous studies have focused on short term treatment models. In this work we have set out to investigate the progressive transforming effects of tobacco smoke on non-tumorigenic mammary epithelial cells and breast cancer cells using in vitro and in vivo models of chronic cigarette smoke exposure.
  
  
  RESULTS
  We show that both non-tumorigenic (MCF 10A, MCF-12A) and tumorigenic (MCF7) breast epithelial cells exposed to cigarette smoke acquire mesenchymal properties such as fibroblastoid morphology, increased anchorage-independent growth, and increased motility and invasiveness. Moreover, transplantation experiments in mice demonstrate that treatment with cigarette smoke extract renders MCF 10A cells more capable to survive and colonize the mammary ducts and MCF7 cells more prone to metastasize from a subcutaneous injection site, independent of cigarette smoke effects on the host and stromal environment. The extent of transformation and the resulting phenotype thus appear to be associated with the differentiation state of the cells at the time of exposure. Analysis by flow cytometry showed that treatment with CSE leads to the emergence of a CD44(hi)/CD24(low) population in MCF 10A cells and of CD44+ and CD49f + MCF7 cells, indicating that cigarette smoke causes the emergence of cell populations bearing markers of self-renewing stem-like cells. The phenotypical alterations induced by cigarette smoke are accompanied by numerous changes in gene expression that are associated with epithelial to mesenchymal transition and tumorigenesis.
  
  
  CONCLUSIONS
  Our results indicate that exposure to cigarette smoke leads to a more aggressive and transformed phenotype in human mammary epithelial cells and that the differentiation state of the cell at the time of exposure may be an important determinant in the phenotype of the final transformed state.
authors.affiliation: Department of Oncology, The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, MD 21287, USA.
authors.forename: Francescopaolo
authors.initials: F
authors.lastname: Di Cello
authors.forename: V Lynn
authors.initials: VL
authors.lastname: Flowers
authors.forename: Huili
authors.initials: H
authors.lastname: Li
authors.forename: Briana
authors.initials: B
authors.lastname: Vecchio-Pagán
authors.forename: Brent
authors.initials: B
authors.lastname: Gordon
authors.forename: Kirsten
authors.initials: K
authors.lastname: Harbom
authors.forename: James
authors.initials: J
authors.lastname: Shin
authors.forename: Robert
authors.initials: R
authors.lastname: Beaty
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Cory
authors.initials: C
authors.lastname: Brayton
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Baylin
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Zahnow
mesh_terms: D000818:Animals; D001940:Breast / Q000378:metabolism / Q000473:pathology; D001943:Breast Neoplasms / Q000209:etiology* / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D061986:MCF-7 Cells; D051379:Mice; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D012907:Smoking / Q000009:adverse effects*; D013234:Stem Cells / Q000378:metabolism
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