title: EGFR is dispensable for c-Met-mediated proliferation and survival activities in mouse adult liver oval cells.
abstract: Liver progenitor cells rise as potential critical players in hepatic regeneration but also carcinogenesis. It is therefore mandatory to define the signals controlling their activation and expansion. Recently, by using a novel in vitro model of oval cell lines expressing a mutant tyrosine kinase-inactive form of c-Met we demonstrated that autocrine c-Met signalling plays an essential role in promoting oval cell survival. Here, we investigated the significance of the epidermal growth factor receptor (EGFR) signalling in oval cell proliferation and survival, as well as a potential functional crosstalk between the c-Met and the EGFR pathways. We found an autocrine activation of the EGFR-triggered pathway in Met(flx/flx) and Met(-/-) oval cells as judged by constitutive expression of the EGFR ligands, transforming growth factor-alpha (TGF-α) and heparin-binding EGF like growth factor (HB-EGF), and activation of EGFR. On the other hand, treatment with AG1478, a specific inhibitor of EGFR, effectively blocked endogenous and EGF-induced proliferation, while increased serum withdrawal and transforming growth factor-beta (TGF-β)-induced apoptosis. These results suggest that constitutively activated EGFR might promote oval cell proliferation and survival. We found that hepatocyte growth factor (HGF) does not transactivate EGFR nor EGF transactivates c-Met. Furthermore, treatment with AG1478 or EGFR gene silencing did not interfere with HGF-mediated activation of target signals, such as protein kinase B (AKT/PKB), and extracellular signal-regulated kinases 1/2 (ERK 1/2), nor did it have any effect on HGF-induced proliferative and antiapoptotic activities in Met(flx/flx) cells, showing that HGF does not require EGFR activation to mediate such responses. EGF induced proliferation and survival equally in Met(flx/flx) and Met(-/-) oval cells, proving that EGFR signalling does not depend on c-Met tyrosine kinase activity. Together, our results provide strong evidence that in normal, untransformed oval cells, c-Met and EGFR represent critical molecular players to control proliferation and survival that function independent of one another.
authors: Dep. Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Madrid, Spain. Electronic address: apalacian@farm.ucm.es.
authors: A
authors: A
authors: Martínez-Palacián
authors: Dep. Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Madrid, Spain. Electronic address: gdelcastillo@iib.uam.es.
authors: G
authors: G
authors: Del Castillo
authors: Dep. Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Madrid, Spain. Electronic address: bm.herrera@farm.ucm.es.
authors: B
authors: B
authors: Herrera
authors: Dep. Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Madrid, Spain. Electronic address: margafdz@farm.ucm.es.
authors: M
authors: M
authors: Fernández
authors: Dep. Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Madrid, Spain. Electronic address: ceronce@farm.ucm.es.
authors: C
authors: C
authors: Roncero
authors: Laboratori d´Oncologia Molecular and Departament de Ciències Fisiològiques II, Universitat de Barcelona, Institut d´Investigació Biomèdica de Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain. Electronic address: ifabregat@idibell.cat.
authors: I
authors: I
authors: Fabregat
authors: Dep. Bioquímica y Biología Molecular II, Facultad de Farmacia, Universidad Complutense, Madrid, Spain. Electronic address: munozas@farm.ucm.es.
authors: A
authors: A
authors: Sánchez
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D015870:Gene Expression; D066257:Heparin-binding EGF-like Growth Factor; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000172:deficiency / Q000235:genetics*; D011799:Quinazolines / Q000494:pharmacology; D015398:Signal Transduction / Q000235:genetics*; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016211:Transforming Growth Factor alpha / Q000235:genetics / Q000378:metabolism; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; C587884:Hbegf protein, mouse; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D011799:Quinazolines; D016211:Transforming Growth Factor alpha; D020032:Tyrphostins; C101044:RTKI cpd; D066246:ErbB Receptors; D019859:Proto-Oncogene Proteins c-met; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases