Combination treatment with Grb7 peptide and Doxorubicin or Trastuzumab (Herceptin) results in cooperative cell growth inhibition in breast cancer cells

Br J Cancer. 2007 May 21;96(10):1520-5. doi: 10.1038/sj.bjc.6603732. Epub 2007 Apr 10.


Grb7 has potential importance in the progression of cancer. We have previously identified a novel peptide that binds to the SH2 domain of Grb7 and inhibits its association with several different receptor tyrosine kinases. We have synthesised the Grb7 peptide, G7-18NATE, with two different cell penetrating peptides, Penetratin and Tat. In this study, we have shown that both Penetratin- and Tat-conjugated G7-18NATE peptides are able to inhibit the proliferation of SK-BR-3, ZR-75-30, MDA-MB-361 and MDA-MB-231 breast cancer cells. There was no significant effects on breast cancer MCF-7cells, non-malignant MCF 10A or 3T3 cells. In addition, there was no significant inhibition of proliferation by Penetratin or Tat alone or by their conjugates with arbitrary peptide sequence in any of the cell lines tested. We determined the EC50 of G7-18NATE-P peptide for SK-BR-3 cell proliferation to be 7.663 x 10(-6) M. Co-treatment of G7-18NATE-P peptide plus Doxorubicin in SK-BR-3 breast cancer cells resulted in an additional inhibition of proliferation, resulting in 56 and 84% decreases in the Doxorubicin EC50 value in the presence of 5 x 10(-6) and 1.0 x 10(-5) M G7-18NATE-P peptide, respectively. Importantly, the co-treatment with Doxorubicin and the delivery peptide did not change the Doxorubicin EC50. Since Grb7 associates with ErbB2, we assessed whether the peptide inhibitor would have a combined effect with a molecule that targets ErbB2, Herceptin. Co-treatment of Herceptin plus 1.0 x 10(-5) M G7-18NATE-P peptide in SK-BR-3 cells resulted in a 46% decrease in the Herceptin EC50 value and no decrease following the co-treatment with Herceptin and penetratin alone. This Grb7 peptide has potential to be developed as a therapeutic agent alone, in combination with traditional chemotherapy, or in combination with other targeting molecules.

Publication types

  • Evaluation Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • Antibodies, Monoclonal / administration & dosage*
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Combined Chemotherapy Protocols / pharmacokinetics
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use*
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / pathology
  • Carcinoma / drug therapy*
  • Carcinoma / pathology
  • Cell Membrane Permeability / drug effects
  • Cell Proliferation / drug effects*
  • Doxorubicin / administration & dosage*
  • Drug Synergism
  • GRB7 Adaptor Protein / administration & dosage*
  • GRB7 Adaptor Protein / chemistry
  • GRB7 Adaptor Protein / pharmacokinetics
  • Humans
  • Mice
  • Peptide Fragments / administration & dosage
  • Peptide Fragments / pharmacokinetics
  • Peptides, Cyclic / administration & dosage
  • Trastuzumab
  • Tumor Cells, Cultured


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • G7-18NATE
  • Peptide Fragments
  • Peptides, Cyclic
  • GRB7 Adaptor Protein
  • Doxorubicin
  • Trastuzumab