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A truncated intracellular HER2/neu receptor produced by alternative RNA processing affects growth of human carcinoma

G K Scott1, R Robles, J W Park

  • 1Cancer Research Institute, University of California, San Francisco 94143-0128.

Molecular and Cellular Biology
|April 1, 1993
PubMed

Insights

Researchers discovered a truncated HER2 receptor transcript in cancer cells, potentially affecting treatment response. This alternative RNA processing generates a secreted HER2 extracellular ligand-binding domain (ECD) that may confer resistance to HER2-targeted therapies.

Area of Science:

  • Molecular Biology
  • Oncology
  • Cancer Research

Background:

  • The HER2 receptor tyrosine kinase is a key driver in several human cancers, particularly breast, gastric, and ovarian cancers.
  • Overexpression of the full-length HER2 receptor is associated with aggressive disease and resistance to certain therapies.
  • Alternative RNA processing can generate novel protein isoforms with potentially altered functions.

Purpose of the Study:

  • To investigate the molecular mechanisms and functional consequences of a truncated HER2 transcript identified in HER2-overexpressing cancer cell lines.
  • To characterize the protein product of the truncated HER2 transcript and its cellular localization.
  • To determine the impact of this truncated HER2 form on the efficacy of anti-HER2 therapies.

Main Methods:

  • Cloning of truncated HER2 sequences from HER2-overexpressing breast cancer cell lines (BT-474, SK-BR-3).
  • RNA analysis using S1 nuclease protection assays to quantify transcript abundance.
  • Expression studies in COS-1 cells and immunofluorescence in MKN7 cells to assess protein production and localization.
  • Metabolic labeling, endoglycosidase studies, and transfection experiments to analyze protein trafficking and therapeutic resistance.

Main Results:

  • A 2.3-kb truncated HER2 transcript, arising from alternative RNA processing, was identified in multiple HER2-amplified tumor cell lines.
  • Expression of the truncated transcript yields a secreted HER2 extracellular ligand-binding domain (ECD) that is concentrated intracellularly.
  • The HER2 ECD exhibits differential trafficking compared to the full-length receptor and can confer resistance to anti-HER2 monoclonal antibodies.

Conclusions:

  • Alternative processing of the HER2 transcript generates a functionally relevant HER2 ECD.
  • Intracellularly sequestered HER2 ECD may play a significant role in the growth regulation of HER2-amplified tumors.
  • The presence and activity of this truncated HER2 form could impact therapeutic strategies and patient outcomes in HER2-driven cancers.

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