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ErbB2 potentiates breast tumor proliferation through modulation of p27(Kip1)-Cdk2 complex formation: receptor

H A Lane1, I Beuvink, A B Motoyama

  • 1Friedrich Miescher Institute, CH-4002 Basel, Switzerland. hlane@fmi.ch

Molecular and Cellular Biology
|April 11, 2000
PubMed

Insights

Antibody 4D5 targets the ErbB2 receptor, inhibiting cancer cell growth by causing a G1 cell cycle arrest. This involves p27(Kip1) protein redistribution, leading to Cdk2 inactivation and cell proliferation reduction in ErbB2-overexpressing tumors.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cell Biology

Background:

  • ErbB2 receptor overexpression drives human cancer development.
  • Anti-ErbB2 monoclonal antibody 4D5 targets ErbB2, inhibiting tumor cell growth.
  • Understanding ErbB2 inhibition's cell cycle effects is crucial for targeted therapies.

Purpose of the Study:

  • To investigate the impact of 4D5-mediated ErbB2 inhibition on the cell cycle of breast tumor cells.
  • To elucidate the molecular mechanisms underlying 4D5-induced G1 arrest.

Main Methods:

  • Treatment of BT474 and SKBR3 breast tumor cell lines with anti-ErbB2 antibody 4D5.
  • Analysis of cell cycle progression, protein dephosphorylation, signal transduction pathways, and protein expression (p27(Kip1), c-Myc, cyclins).
  • Assessment of cyclin-dependent kinase (Cdk) complex activity and p27(Kip1) sequestration.

Main Results:

  • 4D5 treatment induced G1 arrest in BT474 and SKBR3 cells.
  • Key events included ErbB2 dephosphorylation, pathway inhibition, and p27(Kip1) accumulation/redistribution.
  • p27(Kip1) redirection to Cdk2 complexes inactivated Cdk2, preceding G1 block, even without increased p27(Kip1) expression.

Conclusions:

  • ErbB2 overexpression potentiates cyclin E-Cdk2 activity via p27(Kip1) regulation, disrupting G1/S transition.
  • 4D5-induced cell cycle events are specific to ErbB2 inhibition.
  • ErbB2 overexpression alone does not solely determine cellular response to receptor inhibition.

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