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The oncoprotein p28GANK establishes a positive feedback loop in β-catenin signaling

Li-wei Dong1, Guang-zhen Yang, Yu-fei Pan

  • 1International Cooperation Laboratory on Signal Transduction, Eastern Hepatobiliary Surgery Institute, Second Military Medical University, 225 Changhai Road, Shanghai 200438, China.

Cell Research
|June 22, 2011
PubMed

Insights

Gankyrin (p28GANK) promotes hepatocellular carcinoma by upregulating β-catenin independently of p53. This oncoprotein is part of a positive feedback loop involving β-catenin, driving tumor progression.

Area of Science:

  • Oncology
  • Molecular Biology
  • Cancer Research

Background:

  • Gankyrin (p28GANK/PSMD10) is an oncoprotein overexpressed in hepatocellular carcinoma (HCC).
  • Gankyrin degrades tumor suppressors Rb and p53, but its role in β-catenin regulation is unclear.
  • p53 is known to downregulate β-catenin.

Purpose of the Study:

  • To investigate the role of gankyrin (p28GANK) in regulating β-catenin.
  • To elucidate the mechanism by which gankyrin influences β-catenin activity.
  • To explore the potential feedback loop between gankyrin and β-catenin in HCC.

Main Methods:

  • Investigated gankyrin expression regulation by growth factors and Ras via the PI3K-AKT pathway.
  • Assessed the effect of gankyrin on β-catenin transcription activity in p53-deficient cells.
  • Examined E-cadherin levels and β-catenin release upon gankyrin overexpression.
  • Analyzed the transcriptional regulation of gankyrin by β-catenin and c-Myc.
  • Correlated gankyrin, c-Myc, cyclin D1, and β-catenin activation in human HCC samples.

Main Results:

  • Growth factors and Ras upregulate gankyrin via the PI3K-AKT pathway.
  • Gankyrin enhances β-catenin transcription activity independently of p53.
  • Gankyrin reduces E-cadherin, increasing free cytoplasmic β-catenin.
  • Gankyrin expression is upregulated by β-catenin and c-Myc, forming a positive feedback loop.
  • Overexpression of gankyrin, c-Myc, cyclin D1, and β-catenin activation are correlated in HCC.

Conclusions:

  • Gankyrin activates β-catenin through a p53-independent pathway.
  • A positive feedback loop exists between gankyrin and β-catenin, promoting HCC.
  • Gankyrin plays a critical role in HCC tumorigenesis and progression.

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