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[EEF1A2 inhibits the p53 function in hepatocellular carcinoma via PI3K/AKT/mTOR-dependent stabilization of MDM4]

T Longerich1

  • 1Pathologisches Institut, Universitätsklinikum Heidelberg, Im Neuenheimer Feld 224, 69120, Heidelberg, Deutschland, thomas.longerich@med.uni-heidelberg.de.

Der Pathologe
|November 15, 2014
PubMed

Insights

Mouse double minute 4 (MDM4) is upregulated in liver cancer (HCC). The PI3K/AKT/mTOR pathway, regulated by EEF1A2, increases MDM4 levels, suggesting a therapeutic target for HCC patients with poor survival.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • Mouse double minute 4 (MDM4) is frequently upregulated in human hepatocellular carcinoma (HCC).
  • The molecular mechanisms driving MDM4 upregulation in HCC remain poorly understood.
  • The phosphoinositide-3-kinase/v-AKT murine thymoma viral oncogene homolog/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway is implicated in cancer development.

Purpose of the Study:

  • To investigate the role of the PI3K/AKT/mTOR cascade in regulating MDM4 expression in HCC.
  • To identify upstream regulators of this signaling pathway in HCC.
  • To assess the clinical relevance of this pathway in HCC patient outcomes.

Main Methods:

  • Inhibition of PI3K, AKT, and/or mTOR pathways in HCC cell lines.
  • Analysis of MDM4 protein levels, ubiquitination, and phosphorylation.
  • Utilizing a chimeric AKT mouse model for in vivo validation.
  • Assessing eukaryotic elongation factor 1A2 (EEF1A2) expression.
  • Correlating molecular findings with human HCC patient samples and survival data.

Main Results:

  • Inhibition of PI3K-AKT and/or mTOR pathways reduced MDM4 protein levels in HCC cells.
  • MDM4 protein levels are increased by AKT-mediated phosphorylation and de-ubiquitination by ubiquitin-specific protease 2a, protecting it from proteasomal degradation.
  • Overexpression of eukaryotic elongation factor 1A2 (EEF1A2) was linked to PI3K/AKT/mTOR pathway activation.
  • A significant association was observed between EEF1A2, phosphorylated AKT, and MDM4 expression in human HCC samples.
  • Strong activation of the EEF1A2/PI3K/AKT/mTOR/MDM4 axis correlated with shorter survival in HCC patients.

Conclusions:

  • The PI3K/AKT/mTOR pathway, potentially driven by EEF1A2, plays a crucial role in MDM4 upregulation in HCC.
  • MDM4 stabilization through de-ubiquitination and phosphorylation contributes to its elevated levels in HCC.
  • Targeting the EEF1A2/PI3K/AKT/mTOR/MDM4 signaling axis represents a potential therapeutic strategy for a subset of HCC patients, particularly those with poor prognosis.

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