title: Differential HIF-1α and HIF-2α Expression in Mammary Epithelial Cells during Fat Pad Invasion, Lactation, and Involution.
abstract: The development and functional cycle of the mammary gland involves a number of processes that are caricatured by breast cancer cells during invasion and metastasis. Expression of the hypoxia-inducible transcription factors HIF-1 and HIF-2 has been associated with metastatic, poor prognosis, and high-grade breast cancers. Since hypoxia affects normal epithelial differentiation, we hypothesise that HIFs are important for normal breast epithelial development and regeneration as well as cancer initiation and progression. Here, we investigated the expression of the oxygen-sensitive HIF-alpha subunits during mouse mammary gland development, lactation, and involution. In breast epithelial cells, HIF-1α was expressed during early development, prior to cell polarisation. In contrast, expression of HIF-2α occurred later and was restricted to a subpopulation of luminal epithelial cells in the lactating gland. Mammary gland involution is a developmental stage that involves extensive tissue remodelling with cell death but survival of tissue stem/progenitor cells. At this stage, HIF-2α, but little HIF-1α, was expressed in CK14-positive epithelial cells. The temporal but differential expression of the HIF-alpha subunits during the mammary gland life cycle indicates that their expression is controlled by additional factors to hypoxia. Further functional studies of the roles of these proteins in the mammary gland and breast cancer are warranted.
authors.affiliation: Department of Laboratory Medicine Lund, Translational Cancer Research, Lund University Cancer Center at Medicon Village, Lund University, Lund, Sweden.
authors.forename: Sven
authors.initials: S
authors.lastname: Påhlman
authors.affiliation: Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Leif R
authors.initials: LR
authors.lastname: Lund
authors.affiliation: Department of Laboratory Medicine Lund, Translational Cancer Research, Lund University Cancer Center at Medicon Village, Lund University, Lund, Sweden.
authors.forename: Annika
authors.initials: A
authors.lastname: Jögi
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D015687:Cell Hypoxia; D002478:Cells, Cultured; D024141:Collagen Type IV / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005260:Female; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D007150:Immunohistochemistry; D053547:Keratin-14 / Q000378:metabolism; D007774:Lactation; D061986:MCF-7 Cells; D008321:Mammary Glands, Animal / Q000166:cytology / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D024141:Collagen Type IV; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D053547:Keratin-14; D000099162:Endothelial PAS Domain-Containing Protein 1