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Endogenous anti-HER2 antibodies block HER2 phosphorylation and signaling through extracellular signal-regulated

R Bruce Montgomery1, Ekram Makary, Kathy Schiffman

  • 1Division of Oncology, Department of Medicine, VA Puget Sound HCS/University of Washington, Seattle, WA 98108, USA. rbmontgo@u.washington.edu

Cancer Research
|February 8, 2005
PubMed

Insights

Endogenous antibodies targeting the HER2 oncoprotein can suppress its signaling in breast cancer cells. This discovery offers new insights into HER2-targeted therapies and immune responses.

Area of Science:

  • Immunology
  • Oncology
  • Molecular Biology

Background:

  • Monoclonal antibodies targeting the HER2 oncoprotein are crucial in advanced breast cancer treatment.
  • The role of endogenous antibodies in modulating HER2 activity remains largely unexplored.
  • HER2 (Human Epidermal growth factor Receptor 2) is a key oncoprotein in certain breast cancers.

Purpose of the Study:

  • To investigate whether endogenous antibodies can modulate HER2 activity.
  • To determine the effects of induced anti-HER2 antibodies on HER2 signaling and tumor cell phenotype.

Main Methods:

  • Vaccination of patients with HER2 peptides to induce endogenous antibodies.
  • Analysis of antibody specificity, avidity, and isotype (predominantly IgG3).
  • Assessment of antibody effects on HER2 phosphorylation (Y1248), extracellular signal-regulated kinase (ERK) phosphorylation, and colony formation in soft agar.

Main Results:

  • A subset of induced endogenous antibodies suppressed HER2 phosphorylation at Y1248, a critical signaling residue.
  • These antibodies also reduced ERK phosphorylation and inhibited colony formation in soft agar, indicating suppression of the transformed phenotype.
  • Antibody specificity was predominantly directed towards amino acids 328–345 and 369–384 of HER2.
  • The induced antibodies were mainly of the IgG3 isotype with low avidity, suggesting a Th1 immune response.

Conclusions:

  • Endogenous anti-HER2 antibodies can effectively suppress HER2 kinase activity and downstream signaling pathways.
  • These antibodies inhibit the transformed phenotype of HER2-expressing tumor cells, offering potential therapeutic implications.
  • The findings highlight the potential of endogenous antibody responses in HER2-targeted cancer therapy.

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