title: Hedgehog signaling and Bmi-1 regulate self-renewal of normal and malignant human mammary stem cells.
abstract: The epithelial components of the mammary gland are thought to arise from stem cells with a capacity for self-renewal and multilineage differentiation. Furthermore, these cells and/or their immediate progeny may be targets for transformation. We have used both in vitro cultivation and a xenograft mouse model to examine the role of hedgehog signaling and Bmi-1 in regulating self-renewal of normal and malignant human mammary stem cells. We show that hedgehog signaling components PTCH1, Gli1, and Gli2 are highly expressed in normal human mammary stem/progenitor cells cultured as mammospheres and that these genes are down-regulated when cells are induced to differentiate. Activation of hedgehog signaling increases mammosphere-initiating cell number and mammosphere size, whereas inhibition of the pathway results in a reduction of these effects. These effects are mediated by the polycomb gene Bmi-1. Overexpression of Gli2 in mammosphere-initiating cells results in the production of ductal hyperplasia, and modulation of Bmi-1 expression in mammosphere-initiating cells alters mammary development in a humanized nonobese diabetic-severe combined immunodeficient mouse model. Furthermore, we show that the hedgehog signaling pathway is activated in human breast "cancer stem cells" characterized as CD44+CD24-/lowLin-. These studies support a cancer stem cell model in which the hedgehog pathway and Bmi-1 play important roles in regulating self-renewal of normal and tumorigenic human mammary stem cells.
authors.affiliation: Comprehensive Cancer Center, Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109-0946, USA.
authors.forename: Suling
authors.initials: S
authors.lastname: Liu
authors.forename: Gabriela
authors.initials: G
authors.lastname: Dontu
authors.forename: Ilia D
authors.initials: ID
authors.lastname: Mantle
authors.forename: Shivani
authors.initials: S
authors.lastname: Patel
authors.forename: Nam-shik
authors.initials: NS
authors.lastname: Ahn
authors.forename: Kyle W
authors.initials: KW
authors.lastname: Jackson
authors.forename: Prerna
authors.initials: P
authors.lastname: Suri
authors.forename: Max S
authors.initials: MS
authors.lastname: Wicha
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D005260:Female; D053823:Hedgehog Proteins; D006801:Humans; D051741:Kruppel-Like Transcription Factors / Q000096:biosynthesis / Q000235:genetics; D042361:Mammary Glands, Human / Q000166:cytology / Q000378:metabolism; D051379:Mice; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D063150:Polycomb Repressive Complex 1; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D015534:Trans-Activators / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014183:Transplantation, Heterologous; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2
chemical_list: C069077:BMI1 protein, human; C000618551:Gli2 protein, mouse; D053823:Hedgehog Proteins; D051741:Kruppel-Like Transcription Factors; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000071676:Zinc Finger Protein GLI1; D000075746:Zinc Finger Protein Gli2; D063150:Polycomb Repressive Complex 1