Blockade of epidermal growth factor- or heregulin-dependent ErbB2 activation with the anti-ErbB2 monoclonal antibody 2C4 has divergent downstream signaling and growth effects.
Due to heterodimerization and a variety of stimulating ligands, the ErbB receptor system is both diverse and flexible, which proves particularly advantageous to the aberrant signaling of cancer cells. However, specific mechanisms of how a particular receptor contributes to generating the flexibility that leads to aberrant growth regulation have not been well described. We compared the utilization of ErbB2 in response to epidermal growth factor (EGF) and heregulin stimulation in colon carcinoma cells. Anti-ErbB2 monoclonal antibody 2C4 blocked heregulin-stimulated phosphorylation of ErbB2 and ErbB3; activation of mitogen-activated protein kinase (MAPK), phosphatidylinositol 3'-kinase (PI3K), and Akt; proliferation; and anchorage-independent growth. 2C4 blocked EGF-mediated phosphorylation of ErbB2 and inhibited PI3K/Akt and anchorage-independent growth but did not affect ErbB1 or MAPK. Immunoprecipitations showed that ErbB3 and Grb2-associated binder (Gab) 1 were phosphorylated and associated with PI3K activity after heregulin treatment and that Gab1 and Gab2, but not ErbB3, were phosphorylated and associated with PI3K activity after EGF treatment. These data show that monoclonal antibody 2C4 inhibited all aspects of heregulin signaling as well as anchorage-independent and monolayer growth. Furthermore, we identify ErbB2 as a critical component of EGF signaling to the Gab1/Gab2-PI3K-Akt pathway and anchorage-independent growth, but EGF stimulation of MAPK and monolayer growth can occur efficiently without the contribution of ErbB2.
Jackson
James G
JG
Department of Surgery, University of Texas Health Science Center, San Antonio, Texas, USA.
St  Clair
Patricia
P
Sliwkowski
Mark X
MX
Brattain
Michael G
MG
D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000201:enzymology / Q000473:pathology; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020890:Neuregulin-1 / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020890:Neuregulin-1; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D019000:Phosphotyrosine; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D018719:Erb-b2 Receptor Tyrosine Kinases; C490895:GAB2 protein, human; C494918:AKT1 protein, human