title: Control of density-dependent, cell state-specific signal transduction by the cell adhesion molecule CEACAM1, and its influence on cell cycle regulation.
abstract: Growth factor receptors, extracellular matrix receptors, and cell-cell adhesion molecules co-operate in regulating the activities of intracellular signaling pathways. Here, we demonstrate that the cell adhesion molecule CEACAM1 co-regulates growth-factor-induced DNA synthesis in NBT-II epithelial cells in a cell-density-dependent manner. CEACAM1 exerted its effects by regulating the activity of the Erk 1/2 MAP kinase pathway and the expression levels of the cyclin-dependent kinase inhibitor p27(Kip1). Interestingly, both inhibitory and stimulatory effects were observed. Confluent cells continuously exposed to fetal calf serum showed little Erk activity and DNA synthesis compared with sparse cells. Under these conditions, anti-CEACAM1 antibodies strongly stimulated Erk activation, decreased p27 expression, and induced DNA synthesis. In serum-starved confluent cells, re-addition of 10% fetal calf serum activated the Erk pathway, decreased p27 expression, and stimulated DNA synthesis to the same levels as in sparse cells. Under these conditions anti-CEACAM1 antibodies de-activated Erk, restored the level of p27, and inhibited DNA synthesis. These data indicate that CEACAM1 mediates contact inhibition of proliferation in cells that are constantly exposed to growth factors, but co-activates growth-factor-induced proliferation in cells that have been starved for growth factors; exposure to extracellular CEACAM1 ligands reverts these responses.
authors.affiliation: Department of Cell and Molecular Biology, Medical Nobel Institute, Box 285, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
authors.forename: Inka
authors.initials: I
authors.lastname: Scheffrahn
authors.forename: Bernhard B
authors.initials: BB
authors.lastname: Singer
authors.forename: Kristmundur
authors.initials: K
authors.lastname: Sigmundsson
authors.forename: Lothar
authors.initials: L
authors.lastname: Lucka
authors.forename: Björn
authors.initials: B
authors.lastname: Obrink
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000276:immunology / Q000502:physiology*; D000943:Antigens, Differentiation / Q000276:immunology / Q000502:physiology*; D015815:Cell Adhesion Molecules; D002452:Cell Count; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003260:Contact Inhibition / Q000502:physiology*; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000502:physiology; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D051381:Rats; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000943:Antigens, Differentiation; C069847:CD66 antigens; C493962:Cdkn1b protein, rat; D015815:Cell Adhesion Molecules; D018797:Cell Cycle Proteins; D016895:Culture Media, Serum-Free; D005419:Flavonoids; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D048049:Extracellular Signal-Regulated MAP Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one