title: BRCA1 basal-like breast cancers originate from luminal epithelial progenitors and not from basal stem cells.
abstract: Breast cancers in BRCA1 mutation carriers frequently have a distinctive basal-like phenotype. It has been suggested that this results from an origin in basal breast epithelial stem cells. Here, we demonstrate that deleting Brca1 in mouse mammary epithelial luminal progenitors produces tumors that phenocopy human BRCA1 breast cancers. They also resemble the majority of sporadic basal-like breast tumors. However, directing Brca1 deficiency to basal cells generates tumors that express molecular markers of basal breast cancers but do not histologically resemble either human BRCA1 or the majority of sporadic basal-like breast tumors. These findings support a derivation of the majority of human BRCA1-associated and sporadic basal-like tumors from luminal progenitors rather than from basal stem cells. They also demonstrate that when target cells for transformation have the potential for phenotypic plasticity, tumor phenotypes may not directly reflect histogenesis. This has important implications for cancer prevention strategies.
authors.affiliation: The Breakthrough Breast Cancer Research Centre, The Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK.
authors.forename: Gemma
authors.initials: G
authors.lastname: Molyneux
authors.forename: Felipe C
authors.initials: FC
authors.lastname: Geyer
authors.forename: Fiona-Ann
authors.initials: FA
authors.lastname: Magnay
authors.forename: Afshan
authors.initials: A
authors.lastname: McCarthy
authors.forename: Howard
authors.initials: H
authors.lastname: Kendrick
authors.forename: Rachael
authors.initials: R
authors.lastname: Natrajan
authors.forename: Alan
authors.initials: A
authors.lastname: Mackay
authors.forename: Anita
authors.initials: A
authors.lastname: Grigoriadis
authors.forename: Andrew
authors.initials: A
authors.lastname: Tutt
authors.forename: Alan
authors.initials: A
authors.lastname: Ashworth
authors.forename: Jorge S
authors.initials: JS
authors.lastname: Reis-Filho
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Smalley
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000209:etiology / Q000473:pathology*; D004847:Epithelial Cells / Q000166:cytology* / Q000473:pathology; D019398:Genes, BRCA1; D006801:Humans; D051379:Mice; D010641:Phenotype; D013234:Stem Cells / Q000166:cytology* / Q000473:pathology