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Dual blockade of HER2 in HER2-overexpressing tumor cells does not completely eliminate HER3 function

Joan T Garrett1, Cammie R Sutton, María Gabriela Kuba

  • 1Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.

Clinical Cancer Research : an Official Journal of the American Association for Cancer Research
|December 11, 2012
PubMed
Abstract

Insights

Targeting HER3 complements dual HER2 blockade in breast cancer. Suppressing HER3 enhances antitumor effects and improves survival in HER2-overexpressing cancers resistant to existing therapies.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cancer Therapeutics

Background:

  • Dual blockade of HER2 (Human Epidermal growth factor Receptor 2) with trastuzumab and lapatinib is effective but not curative for HER2-overexpressing breast cancers.
  • HER2-targeted therapies can lead to compensatory upregulation of HER3 (Human Epidermal growth factor Receptor 3), a mechanism of resistance.
  • The PI3K/AKT pathway is a critical downstream signaling pathway for HER2 and HER3, and its inhibition can influence receptor expression.

Purpose of the Study:

  • To investigate if suppressing HER3 synergizes with dual HER2 blockade in HER2-overexpressing breast cancer.
  • To determine if targeting HER3 can overcome resistance to HER2-directed therapies.
  • To evaluate the impact of combined HER2 and HER3 inhibition on tumor growth and survival.

Main Methods:

  • Utilized Western blotting to assess HER2 and HER3 inhibition in HER2-positive breast cancer cell lines.
  • Conducted in vitro assays to measure drug-induced apoptosis and 2D/3D cell growth.
  • Performed in vivo studies using xenograft models to evaluate tumor growth inhibition and survival rates with combination therapies.

Main Results:

  • The HER3-neutralizing antibody U3-1287 blocked lapatinib and trastuzumab-induced HER3 upregulation.
  • U3-1287 enhanced the antitumor activity of dual HER2 blockade in both sensitive and resistant cells.
  • Combination therapy with lapatinib, trastuzumab, and U3-1287 reduced tumor recurrence and improved survival in xenograft models.

Conclusions:

  • Dual HER2 blockade alone does not fully overcome compensatory HER3 upregulation in HER2-overexpressing breast cancer.
  • Therapeutic inhibition of HER3 should be integrated into multidrug regimens to effectively target the HER2 network.
  • Targeting HER3 offers a promising strategy to enhance efficacy and overcome resistance in HER2-positive breast cancer treatment.

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