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Pancreatic tumours escape from translational control through 4E-BP1 loss

Y Martineau1, R Azar2, D Müller1

  • 1Université de Toulouse, Centre de Recherche en Cancérologie de Toulouse (CRCT), Equipe Labellisée Ligue Contre le Cancer and Laboratoire d'Excellence Toulouse Cancer, INSERM UMR-1037, Toulouse, France.

Oncogene
|April 9, 2013
PubMed

Insights

Pancreatic cancer often loses 4E-BP1, a protein that inhibits cell growth. This loss promotes tumor development and resistance to mTOR inhibitors, but new drugs may overcome this.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • The eukaryotic translation initiation factor 4E (eIF4E) plays a role in cell transformation when phosphorylated.
  • eIF4E activity is regulated by inhibitory eIF4E-binding proteins (4E-BPs), which are targets of the mTOR kinase.
  • 4E-BP1 and 4E-BP2 are crucial for the antiproliferative effects of mTOR inhibitors.

Purpose of the Study:

  • To investigate the role of 4E-BP1 and 4E-BP2 in pancreatic ductal adenocarcinoma (PDAC).
  • To determine the impact of 4E-BP1 downregulation on eIF4E activity and PDAC progression.
  • To assess the potential of targeting 4E-BP1/2 pathways for PDAC treatment.

Main Methods:

  • Analysis of 4E-BP1 and 4E-BP2 expression in human PDAC and a Kras-driven mouse model.
  • Assessment of eIF4E phosphorylation, protein synthesis, and cell proliferation in vitro and in vivo.
  • Evaluation of resistance to mTOR inhibitors upon 4E-BP1/2 loss.
  • Testing of a novel compound mimicking 4E-BP function.

Main Results:

  • Pancreas specifically expresses high levels of 4E-BP1, with 4E-BP2 being nearly undetectable.
  • 4E-BP1 expression is lost in over half of human PDAC cases and in a Kras-driven mouse model.
  • 4E-BP1 downregulation increases eIF4E phosphorylation, promoting PDAC cell proliferation and tumor growth.
  • Loss of 4E-BP1 and 4E-BP2 confers resistance to mTOR inhibitors by maintaining eIF4E phosphorylation and protein synthesis.

Conclusions:

  • 4E-BP1 is a critical tumor suppressor in the pancreas, and its loss is a frequent event in PDAC.
  • 4E-BP1 downregulation contributes to PDAC pathogenesis by enhancing eIF4E activity and promoting proliferation.
  • Combined loss of 4E-BP1 and 4E-BP2 leads to resistance to mTOR-targeted therapies.
  • Compounds that mimic 4E-BP function independently of mTOR inhibition show promise for PDAC treatment.

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