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Breast cancer-associated PIK3CA mutations are oncogenic in mammary epithelial cells

Steven J Isakoff1, Jeffrey A Engelman, Hanna Y Irie

  • 1Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.

Cancer Research
|December 3, 2005
PubMed

Insights

Mutations in the PIK3CA gene, common in breast cancer, activate the phosphoinositide 3-kinase (PI3K) pathway. These PIK3CA mutations drive tumor-like cell changes and may be targets for cancer therapy.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Biology

Background:

  • The phosphoinositide 3-kinase (PI3K) pathway is crucial in various cancers.
  • Mutations in PIK3CA, encoding the p110alpha subunit, are frequent in human cancers, particularly breast cancer (18-40%).
  • Specific PIK3CA mutations in exons 9 and 20 are common, but their functional impact in breast cells is unclear.

Purpose of the Study:

  • To investigate the phenotypic effects of common PIK3CA mutations (E545K and H1047R) in breast epithelial cells.
  • To assess the PI3K activity and sensitivity to inhibition of these mutant forms.
  • To evaluate the impact of mutant p110alpha on breast cell characteristics relevant to tumorigenesis.

Main Methods:

  • Utilized the MCF-10A immortalized breast epithelial cell line.
  • Expressed common PIK3CA variants (E545K, H1047R) and wild-type p110alpha.
  • Assessed PI3K activity, proliferation (anchorage-independent, growth factor-independent), anoikis resistance, drug sensitivity (paclitaxel), and 3D morphogenesis.

Main Results:

  • Both E545K and H1047R mutants showed increased PI3K activity compared to wild-type but remained sensitive to PI3K inhibitors.
  • Expression of mutant p110alpha induced tumor-like phenotypes: anchorage-independent growth, growth factor-independent proliferation, and anoikis resistance.
  • Mutant isoforms conferred paclitaxel resistance and disrupted normal mammary acinar development in 3D cultures.

Conclusions:

  • Cancer-associated PIK3CA mutations significantly alter breast epithelial cell phenotypes, promoting characteristics of tumor cells.
  • These findings support the role of PIK3CA mutations in breast cancer development.
  • Mutant PIK3CA isoforms represent promising therapeutic targets for breast cancer treatment.

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