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Fbxw7 contributes to tumor suppression by targeting multiple proteins for ubiquitin-dependent degradation

Yo Fujii1, Masayoshi Yada, Masaaki Nishiyama

  • 1Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582.

Cancer Science
|July 26, 2006
PubMed

Insights

Loss of Fbxw7, a key tumor suppressor, leads to the accumulation of cell-cycle promoters like cyclin E and c-Myc. This accumulation drives cancer cell proliferation and growth, highlighting Fbxw7

Area of Science:

  • * Molecular biology
  • * Cancer research
  • * Cell cycle regulation

Background:

  • * Fbxw7 (F-box and WD repeat domain-containing protein 7) is an SCF ubiquitin ligase component.
  • * Fbxw7 targets cell-cycle promoters and oncogenic proteins like cyclin E, c-Myc, and Aurora-A for degradation.
  • * Loss of Fbxw7 function is implicated in oncogenesis due to substrate accumulation.

Purpose of the Study:

  • * To investigate the relationship between Fbxw7 mutations and the accumulation of its substrates (cyclin E, c-Myc, Aurora-A) in cancer cells.
  • * To determine which accumulating substrate is most critical for cancer development in Fbxw7-mutant cells.
  • * To assess the impact of substrate accumulation on cancer cell proliferation and growth.

Main Methods:

  • * Analysis of cyclin E, c-Myc, and Aurora-A protein levels in seven cancer cell lines with wild-type or mutant Fbxw7.
  • * Forced expression of Fbxw7 in mutant cells to observe substrate level changes.
  • * RNA interference to decrease cyclin E, c-Myc, or Aurora-A expression in Fbxw7-mutant cells.
  • * Assessment of cell proliferation and anchorage-independent growth rates.

Main Results:

  • * Fbxw7-mutant cancer cells showed elevated levels of cyclin E, c-Myc, and Aurora-A, though the extent varied.
  • * Forced Fbxw7 expression reduced these substrate levels in mutant cells.
  • * Depletion of cyclin E, c-Myc, or Aurora-A significantly inhibited proliferation and anchorage-independent growth of Fbxw7-mutant cells.

Conclusions:

  • * Loss of Fbxw7 function leads to the accumulation of multiple growth-promoting substrates, including cyclin E, c-Myc, and Aurora-A.
  • * These accumulated substrates are essential for the proliferation and growth of Fbxw7-mutant cancer cells.
  • * Fbxw7's role in regulating multiple targets is crucial for suppressing cancer development.

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