title: EGF-induced Grb7 recruits and promotes Ras activity essential for the tumorigenicity of Sk-Br3 breast cancer cells.
abstract: Co-amplification and co-overexpression of ErbB2 and Grb7 are frequently found in various cancers, including breast cancer. Biochemical and functional correlations of the two molecules have identified Grb7 to be a pivotal mediator downstream of ErbB2-mediated oncogenesis. However, it remains largely unknown how Grb7 is involve in the ErbB2-mediated tumorigenesis. In this study, we show that Grb7-mediated cell proliferation and growth are essential for the tumorigenesis that occurs in ErbB2-Grb7-overexpressing breast cancer cells. Intrinsically, EGF-induced de novo Grb7 tyrosine phosphorylation/activation recruits and activates Ras-GTPases and subsequently promotes the phosphorylation of ERK1/2, thereby stimulating tumor growth. Furthermore, we also found the anti-tumor effect could be synergized by co-treatment with Herceptin plus Grb7 knockdown in Sk-Br3 breast cancer cells. Our findings illustrate an underlying mechanism by which Grb7 promotes tumorigenesis through the formation of a novel EGFR-Grb7-Ras signaling complex, thereby highlighting the potential strategy of targeting Grb7 as an anti-breast cancer therapy.
authors.affiliation: Department of Plant Pathology and Microbiology, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Pei-Yu
authors.initials: PY
authors.lastname: Chu
authors.forename: Tsai-Kun
authors.initials: TK
authors.lastname: Li
authors.forename: Shih-Torng
authors.initials: ST
authors.lastname: Ding
authors.forename: I-Rue
authors.initials: IR
authors.lastname: Lai
authors.forename: Tang-Long
authors.initials: TL
authors.lastname: Shen
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use; D061067:Antibodies, Monoclonal, Humanized; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000235:genetics / Q000494:pharmacology; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005260:Female; D051382:GRB7 Adaptor Protein / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D016513:Mice, SCID; D041681:NIH 3T3 Cells; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D000068878:Trastuzumab; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D051382:GRB7 Adaptor Protein; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D018631:ras Proteins; D000068878:Trastuzumab