Functional interaction between mouse erbB3 and wild-type rat c-neu in transgenic mouse mammary tumor cells

Breast Cancer Res. 2005;7(5):R708-18. doi: 10.1186/bcr1281. Epub 2005 Jul 6.


Introduction: Co-expression of several receptor tyrosine kinases (RTKs), including erbB2 and erbB3, is frequently identified in breast cancers. A member of the RTK family, the kinase-deficient erbB3 can activate downstream signaling via heterodimer formation with erbB2. We studied the expression of RTK receptors in mammary tumors from the wild-type (wt) rat c-neu transgenic model. We hypothesized that physical and functional interactions between the wt rat neu/ErbB2 transgene and mouse ErbB3-encoded proteins could occur, activating downstream signaling and promoting mammary oncogenesis.

Methods: Immunohistochemical and Western blot analyses were performed to study the expression of rat c-neu/ErbB2 and mouse erbB3 in mammary tumors and tumor-derived cell lines from the wt rat c-neu transgenic mice. Co-immunoprecipitation methods were employed to quantitate heterodimerization between the transgene-encoded protein erbB2 and the endogenous mouse erbB3. Tumor cell growth in response to growth factors, such as Heregulin (HRG), epidermal growth factor (EGF), or insulin-like growth factor-1 (IGF-1), was also studied. Post-HRG stimulation, activation of the RTK downstream signaling was determined by Western blot analyses using antibodies against phosphorylated Akt and mitogen-activated protein kinase (MAPK), respectively. Specific inhibitors were then used with cell proliferation assays to study the phosphoinositide-3 kinase (PI-3K)/Akt and MAPK kinase (MEK)/MAPK pathways as possible mechanisms of HRG-induced tumor cell proliferation.

Results: Mammary tumors and tumor-derived cell lines frequently exhibited elevated co-expression of erbB2 and erbB3. The transgene-encoded protein erbB2 formed a stable heterodimer complex with endogenous mouse erbB3. HRG stimulation promoted physical and functional erbB2/erbB3 interactions and tumor cell growth, whereas no response to EGF or IGF-1 was observed. HRG treatment activated both the Akt and MAPK pathways in a dose- and time-dependent manner. Both the PI-3K inhibitor LY 294002 and MEK inhibitor PD 98059 significantly decreased the stimulatory effect of HRG on tumor cell proliferation.

Conclusion: The co-expression of wt rat neu/ErbB2 transgene and mouse ErbB3, with physical and functional interactions between these two species of RTK receptors, was demonstrated. These data strongly suggest a role for erbB3 in c-neu (ErbB2)-associated mammary tumorigenesis, as has been reported in human breast cancers.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Breast Neoplasms
  • Cell Division
  • Cell Line, Tumor
  • DNA, Neoplasm / genetics
  • Gene Expression Regulation, Neoplastic
  • Glycoproteins / genetics*
  • Glycoproteins / metabolism
  • Humans
  • Immunohistochemistry
  • Mammary Neoplasms, Animal / genetics*
  • Mammary Neoplasms, Animal / pathology
  • Mice
  • Mice, Transgenic
  • Rats
  • Receptor, ErbB-2
  • Receptor, ErbB-3 / genetics*
  • Receptor, ErbB-3 / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction


  • DNA, Neoplasm
  • Glycoproteins
  • Erbb2 protein, rat
  • Receptor, ErbB-2
  • Receptor, ErbB-3