title: Accelerated mammary tumor onset in a HER2/Neu mouse model exposed to DDT metabolites locally delivered to the mammary gland.
abstract: BACKGROUND
  The association of DDT (dichlorodiphenyltrichloroethane) with breast cancer is controversial, but animal studies directly linking DDT to risk are lacking. Concerns with DDT reside in its environmental persistence, bioaccumulation in breast adipose tissue, and endocrine-disrupting actions. Whereas most attention has been focused on estrogenic congeners, we tested the cancer-inducing potential of the antiandrogen, p,p´-DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene], the most prevalent and persistent DDT metabolite.
  
  
  OBJECTIVE
  We aimed to determine whether developmental exposure to p,p´-DDE stored in adipose tissue surrounding the cancer-prone mammary epithelium of MMTV-Neu mice influences tumor development.
  
  
  METHODS
  For localized delivery, Elvax 40P pellets containing p,p´-DDE were implanted into the mammary fat pads of prepubertal female mice. We compared mammary tumor development with p,p´-DDE with development in response to its estrogenic isomer, o,p´-DDE [1,1-dichloro-2-(o-chlorophenyl)-2-(p-chlorophenyl) ethylene], and a mixture of both isomers.
  
  
  RESULTS
  p,p´-DDE implants significantly accelerated mammary tumor onset compared with vehicle Elvax implants. o,p´-DDE had similar results, but only at ≤ 10 months of age. Lipid-adjusted levels of p,p´-DDE in mammary adipose tissue and serum in young mice were within the ranges of human exposure, whereas concentrations in aged mice were low to undetectable. Exposure to a 2:1 ratio of p,p´-DDE:o,p´-DDE did not result in the younger latency observed with the individual isomers.
  
  
  CONCLUSIONS
  p,p´-DDE exposure at concentrations relevant to human exposure accelerates mammary carcinogenesis in mice, possibly through hormonal and/or other actions. These data suggest that DDE exposure would promote, but not cause, mammary tumorigenesis. Developmental exposure in immature mammary tissue continues to affect tumor onset even after p,p´-DDE levels have declined. Future studies are needed to determine whether early exposure to p,p´-DDE correspondingly predisposes women to early-onset breast cancer.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Duquesne University, Pittsburgh, Pennsylvania 16214-1232, USA.
authors.forename: Nakpangi A
authors.initials: NA
authors.lastname: Johnson
authors.forename: Arline
authors.initials: A
authors.lastname: Ho
authors.forename: J Mark
authors.initials: JM
authors.lastname: Cline
authors.forename: Claude L
authors.initials: CL
authors.lastname: Hughes
authors.forename: Warren G
authors.initials: WG
authors.lastname: Foster
authors.forename: Vicki L
authors.initials: VL
authors.lastname: Davis
mesh_terms: D000818:Animals; D003634:DDT / Q000633:toxicity*; D004195:Disease Models, Animal; D018734:Genes, erbB-2; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced / Q000235:genetics / Q000473:pathology*; D051379:Mice
chemical_list: D003634:DDT