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Integrin alpha 6 beta 4 promotes migration, invasion through Tiam1 upregulation, and subsequent Rac activation.

Abstract
The lethality of pancreatic adenocarcinoma stems from an elevated incidence of tumor cell invasion and metastasis that are mediated by mechanisms not yet understood. Recent studies indicate that the proinvasive integrin alpha 6 beta 4 is highly upregulated in pancreatic adenocarcinomas. To assess the importance of this integrin in pancreatic cancer cell migration and invasion, cell lines were screened for integrin alpha 6 beta 4 expression by immunoblotting and fluorescence-activated cell sorting and their ability to migrate and invade toward hepatocyte growth factor (HGF). We found that cell surface expression of the alpha 6 beta 4 integrin correlated with the cells' ability to migrate and invade toward HGF. When cells expressing high levels of integrin alpha 6 beta 4 were treated with small interfering RNA targeting alpha 6 or beta 4 integrin subunits, we observed a reduction in cell migration and invasion. Furthermore, the activity of the small GTPase Rac1 was stimulated by alpha 6 beta 4 integrin expression and was necessary for HGF-stimulated chemotaxis. We discovered that expression of the Rac-specific nucleotide exchange factor, Tiam1 (T-lymphoma invasion and metastasis), was upregulated in cells overexpressing the integrin alpha 6 beta 4 and required for the elevated Rac1 activity in these cells. We conclude that the integrin alpha 6 beta 4 promotes the migratory and invasive phenotype of pancreatic carcinoma cells through the Tiam1-Rac1 pathway in part through the upregulation of Tiam1.
AuthorsZobeida Cruz-Monserrate, Kathleen L O'Connor
JournalNeoplasia (New York, N.Y.) (Neoplasia) Vol. 10 Issue 5 Pg. 408-17 (May 2008) ISSN: 1476-5586 [Electronic] Canada
PMID18472958 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)
Chemical References
  • Guanine Nucleotide Exchange Factors
  • Integrin alpha6beta4
  • RAC1 protein, human
  • RNA, Small Interfering
  • TIAM1 protein, human
  • Hepatocyte Growth Factor
  • rac1 GTP-Binding Protein
Topics
  • Adenocarcinoma (metabolism, pathology)
  • Cell Adhesion
  • Cell Movement
  • Chemotaxis
  • Guanine Nucleotide Exchange Factors (antagonists & inhibitors, genetics, metabolism)
  • Hepatocyte Growth Factor (pharmacology)
  • Humans
  • Integrin alpha6beta4 (physiology)
  • Neoplasm Invasiveness
  • Pancreatic Neoplasms (metabolism, pathology)
  • RNA, Small Interfering (pharmacology)
  • Tumor Cells, Cultured
  • Up-Regulation
  • rac1 GTP-Binding Protein (metabolism)

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