Evaluation of Cyclic Peptide Inhibitors of the Grb7 Breast Cancer Target: Small Change in Cargo Results in Large Change in Cellular Activity

  • Molecules. 2019 Oct 17;24(20):3739. doi: 10.3390/molecules24203739.
Jianrong Sang  1  2 ,  Ketav Kulkarni  3 ,  Gabrielle M Watson  4 ,  Xiuquan Ma  5 ,  David J Craik  6 ,  Sónia T Henriques  7  8 ,  Aaron G Poth  9 ,  Aurélie H Benfield  10  11 ,  Jacqueline A Wilce  12
Affiliations
  • 1. Department of Physiology, School of Medicine, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013, Jiangsu, China. [email protected].
  • 2. Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton 3800, Australia. [email protected].
  • 3. Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton 3800, Australia. [email protected].
  • 4. Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton 3800, Australia. [email protected].
  • 5. Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton 3800, Australia. [email protected].
  • 6. Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia. [email protected].
  • 7. Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia. [email protected].
  • 8. School of Biomedical Sciences, Institute of Health & Biomedical Innovation, Queensland University of Technology, Translational Research Institute, Brisbane 4102, Australia. [email protected].
  • 9. Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia. [email protected].
  • 10. Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia. [email protected].
  • 11. School of Biomedical Sciences, Institute of Health & Biomedical Innovation, Queensland University of Technology, Translational Research Institute, Brisbane 4102, Australia. [email protected].
  • 12. Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton 3800, Australia. [email protected].
PMID: 31627265 DOI: 10.3390/molecules24203739
Abstract

Grb7 is an adapter protein, overexpressed in HER2+ve breast and Other cancers, and identified as a therapeutic target. Grb7 promotes both proliferative and migratory cellular pathways through interaction of its SH2 domain with upstream binding partners including HER2, SHC, and FAK. Here we present the evaluation of a series of monocyclic and bicyclic peptide inhibitors that have been developed to specifically and potently target the Grb7 SH2-domain. All peptides tested were found to inhibit signaling in both ERK and Akt pathways in SKBR-3 and MDA-MB-231 cell lines. Proliferation, migration, and invasion assays revealed, however, that the second-generation bicyclic peptides were not more bioactive than the first generation G7-18NATE peptide, despite their higher in vitro affinity for the target. This was found not to be due to steric hindrance by the cell-permeability tag, as ascertained by ITC, but to differences in the ability of the bicyclic peptides to interact with and penetrate cellular membranes, as determined using SPR and mass spectrometry. These studies reveal that just small differences to amino acid composition can greatly impact the effectiveness of peptide inhibitors to their intracellular target and demonstrate that G7-18NATE remains the most effective peptide inhibitor of Grb7 developed to date.

Keywords
Grb7; SH2-domain; bicyclic peptide; cancer cell migration; cell penetrating peptide; inhibitor binding; invasion; lipid bilayer interactions; mass spectrometry quantification; proliferation.
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