title: Cytokeratin 18 is necessary for initiation of TGF-β1-induced epithelial-mesenchymal transition in breast epithelial cells.
abstract: During epithelial-mesenchymal transition (EMT), epithelial cells lose key phenotypic markers (e.g., E-cadherin and cytokeratin 18) and acquire mesenchymal markers (e.g., N-cadherin and vimentin). Although the loss of cytokeratin 18 is a hallmark of EMT, the regulatory role of cytokeratin 18 in EMT is not yet fully understood. Here, we report that cytokeratin 18 is involved in the regulation of transforming growth factor-beta1 (TGF-β1)-induced EMT in breast epithelial cells. When MCF10A cells were treated with TGF-β1 for 24 h, considerable morphological changes, indicative of the early stages of EMT (e.g., loss of cell-cell contact), were observed and cytokeratin 18 was downregulated. However, E-cadherin levels were not altered until a later time point. This suggests that cytokeratin 18 may play an active role during the earlier stages of EMT. Consistent with this notion, siRNA-mediated knockdown of cytokeratin 18 delayed TGF-β1-mediated EMT, and the associated downregulation of E-cadherin reduced the phosphorylation/nuclear localization of smad 2/3 and decreased the expression levels of snail and slug (which inhibit E-cadherin expression in epithelial cells as an early response to TGF-β1). Taken together, these results suggest that cytokeratin 18 critically contributes to initiating TGF-β1-induced EMT via the smad 2/3-mediated regulation of snail and slug expression in breast epithelial cells.
authors.affiliation: Department of Life Sciences, the Research Center for Cellular Homeostasis, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemoon-Gu, Seoul, 120-750, Korea.
authors.forename: Hyejung
authors.initials: H
authors.lastname: Jung
authors.affiliation: Department of Life Sciences, the Research Center for Cellular Homeostasis, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemoon-Gu, Seoul, 120-750, Korea.
authors.forename: Bomin
authors.initials: B
authors.lastname: Kim
authors.affiliation: Department of Surgery, College of Medicine, Ewha Womans University, 911-1 Mok-Dong Yangcheon-Ku, Seoul, 158-710, Korea. mbit@ewha.ac.kr.
authors.forename: Byung In
authors.initials: BI
authors.lastname: Moon
authors.affiliation: Department of Life Sciences, the Research Center for Cellular Homeostasis, Ewha Womans University, 52, Ewhayeodae-gil, Seodaemoon-Gu, Seoul, 120-750, Korea. ohes@ewha.ac.kr.
authors.forename: Eok-Soo
authors.initials: ES
authors.lastname: Oh
mesh_terms: D001940:Breast / Q000166:cytology / Q000378:metabolism*; D015820:Cadherins / Q000378:metabolism; D045744:Cell Line, Tumor; D058750:Epithelial-Mesenchymal Transition; D005260:Female; D006801:Humans; D053538:Keratin-18 / Q000096:biosynthesis*; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D000071250:Snail Family Transcription Factors / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D015820:Cadherins; D053538:Keratin-18; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C000604407:SNAI1 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D000071250:Snail Family Transcription Factors; C508960:TGFB1 protein, human; D053773:Transforming Growth Factor beta1
keywords: Breast cancer; Cytokeratin 18; E-cadherin; Epithelial–mesenchymal transition; Slug