Blockade of Cripto binding to cell surface GRP78 inhibits oncogenic Cripto signaling via MAPK/PI3K and Smad2/3 pathways

Oncogene. 2009 Jun 18;28(24):2324-36. doi: 10.1038/onc.2009.97. Epub 2009 May 4.

Abstract

Cripto is a developmental oncoprotein that signals via mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3K)/Akt and Smad2/3 pathways. However, the molecular basis for Cripto coupling to these pathways during embryogenesis and tumorigenesis is not fully understood. In this regard, we recently demonstrated that Cripto forms a cell surface complex with the HSP70 family member glucose-regulated protein-78 (GRP78). Here, we provide novel functional evidence demonstrating that cell surface GRP78 is a necessary mediator of Cripto signaling in human tumor, mammary epithelial and embryonic stem cells. We show that targeted disruption of the cell surface Cripto/GRP78 complex using shRNAs or GRP78 immunoneutralization precludes Cripto activation of MAPK/PI3K pathways and modulation of activin-A, activin-B, Nodal and transforming growth factor-beta1 signaling. We further demonstrate that blockade of Cripto binding to cell surface GRP78 prevents Cripto from increasing cellular proliferation, downregulating E-Cadherin, decreasing cell adhesion and promoting pro-proliferative responses to activin-A and Nodal. Thus, disrupting the Cripto/GRP78 binding interface blocks oncogenic Cripto signaling and may have important therapeutic value in the treatment of cancer.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activins / pharmacology
  • Antibodies / pharmacology
  • Blotting, Western
  • Cadherins / metabolism
  • Cell Adhesion / drug effects
  • Cell Line
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Epidermal Growth Factor / genetics
  • Epidermal Growth Factor / metabolism*
  • GPI-Linked Proteins
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / immunology
  • Heat-Shock Proteins / metabolism*
  • Humans
  • Immunoprecipitation
  • Intercellular Signaling Peptides and Proteins
  • Luciferases / genetics
  • Luciferases / metabolism
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism*
  • Microscopy, Confocal
  • Mitogen-Activated Protein Kinases / metabolism*
  • Models, Biological
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Protein Binding / drug effects
  • RNA, Small Interfering / genetics
  • Radioligand Assay
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Smad Proteins / metabolism*
  • Smad2 Protein / metabolism
  • Smad3 Protein / metabolism

Substances

  • Antibodies
  • Cadherins
  • GPI-Linked Proteins
  • Heat-Shock Proteins
  • Intercellular Signaling Peptides and Proteins
  • Membrane Glycoproteins
  • Neoplasm Proteins
  • RNA, Small Interfering
  • SMAD2 protein, human
  • SMAD3 protein, human
  • Smad Proteins
  • Smad2 Protein
  • Smad3 Protein
  • TDGF1 protein, human
  • activin A
  • Activins
  • Epidermal Growth Factor
  • Luciferases
  • Phosphatidylinositol 3-Kinases
  • Mitogen-Activated Protein Kinases
  • molecular chaperone GRP78