title: Ras/MAPK pathway confers basement membrane dependence upon endoderm differentiation of embryonic carcinoma cells.
abstract: The formation of extraembryonic endoderm is one of the earliest steps in the differentiation of pluripotent cells of the inner cell mass during the early stages of embryonic development. The primitive endoderm cells and the derived parietal and visceral endoderm cells gain the capacity to produce collagen IV and laminin. The deposition of these components results in the formation of basement membrane and epithelium of the endoderm, with polarized cells covering the inner surface of the blastocoels. We used retinoic acid-induced endoderm differentiation of stem cell-like F9 embryonic carcinoma cells to study the role of the Ras pathway and its regulation in the formation of the visceral endoderm. Upon endoderm differentiation of F9 cells induced by retinoic acid, c-Fos expression, the downstream target of the Ras pathway, is suppressed by uncoupling Elk-1 phosphorylation/activation to MAPK activity. However, attachment to matrix gel greatly enhances the activation of MAPK in endoderm cells but not in undifferentiated F9 cells. Enhanced MAPK activation as a result of contact with basement membrane is able to compensate for reduced Elk-1 phosphorylation and c-Fos expression. We conclude that endoderm differentiation renders the activation of the Ras pathway basement membrane dependent, contributing to the epithelial organization of the visceral endoderm.
authors.affiliation: Ovarian Cancer and Tumor Cell Biology Programs, Department of Medical Oncology, Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, PA 19111, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Smedberg
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Smith
authors.forename: Callinice D
authors.initials: CD
authors.lastname: Capo-Chichi
authors.forename: Andrey
authors.initials: A
authors.lastname: Frolov
authors.forename: Dong-Hua
authors.initials: DH
authors.lastname: Yang
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Godwin
authors.forename: Xiang-Xi
authors.initials: XX
authors.lastname: Xu
mesh_terms: D000818:Animals; D001485:Basement Membrane / Q000378:metabolism*; D018236:Carcinoma, Embryonal / Q000378:metabolism / Q000473:pathology*; D002454:Cell Differentiation; D002455:Cell Division; D004268:DNA-Binding Proteins; D004707:Endoderm / Q000166:cytology*; D004789:Enzyme Activation; D020935:MAP Kinase Signaling System; D051379:Mice; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D014157:Transcription Factors; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D050807:ets-Domain Protein Elk-1; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C494113:Elk1 protein, mouse; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D014212:Tretinoin; D018631:ras Proteins