Activation of the Ras signalling pathway in human breast cancer cells overexpressing erbB-2

Oncogene. 1994 Dec;9(12):3601-8.


The c-erbB-2 proto-oncogene encodes a receptor tyrosine kinase (RTK) closely related to the epidermal growth factor receptor (EGFR). Overexpression of erbB-2 occurs in approximately 20% of human breast tumours, where increased expression correlates with poor patient prognosis. The EGFR is coupled to the Ras signalling pathway by interaction with the adaptor protein Grb2, and Sos, a Ras GDP-GTP exchange factor. In this study, activation of the erbB-2 receptor and its association with Grb2 and Sos was investigated in breast cancer cell lines which overexpress erbB-2. The receptor was found to be tyrosine phosphorylated in all cell lines in which it is overexpressed. Western blotting of Grb2 and Sos immuneprecipitates from such cells revealed co-precipitation of erbB-2, demonstrating association of the Grb2/Sos complex with erbB-2 in vivo. Furthermore, a fusion protein containing only the SH2 domain of Grb2 bound to erbB-2 immobilized on nitrocellulose, indicating that association with Grb2 is direct and mediated by the SH2 domain of Grb2. The degree of association between the erbB-2 receptor and Grb2 in vivo was related to erbB-2 overexpression, and MAP kinase, which functions downstream from Ras, displayed markedly increased activity in cell lines overexpressing erbB-2. These results demonstrate that erbB-2 is coupled to Ras signalling via the Grb2/Sos complex, and that overexpression of this receptor in breast cancer cells leads to amplification of the Ras signalling pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing*
  • Breast Neoplasms / enzymology
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism*
  • GRB2 Adaptor Protein
  • Gene Expression Regulation, Neoplastic*
  • Genes, erbB-2*
  • Guanine Nucleotide Exchange Factors
  • Humans
  • Mitogen-Activated Protein Kinase 1
  • Phenotype
  • Protein Serine-Threonine Kinases / metabolism
  • Protein-Tyrosine Kinases / metabolism
  • Proteins / metabolism
  • Proto-Oncogene Mas
  • Signal Transduction*
  • Tumor Cells, Cultured
  • ras Guanine Nucleotide Exchange Factors


  • Adaptor Proteins, Signal Transducing
  • GRB2 Adaptor Protein
  • GRB2 protein, human
  • Guanine Nucleotide Exchange Factors
  • MAS1 protein, human
  • Proteins
  • Proto-Oncogene Mas
  • ras Guanine Nucleotide Exchange Factors
  • Protein-Tyrosine Kinases
  • Protein Serine-Threonine Kinases
  • Mitogen-Activated Protein Kinase 1