Silencing of D4-GDI inhibits growth and invasive behavior in MDA-MB-231 cells by activation of Rac-dependent p38 and JNK signaling

J Biol Chem. 2009 May 8;284(19):12956-65. doi: 10.1074/jbc.M807845200. Epub 2009 Mar 6.

Abstract

The Rho GDP dissociation inhibitor D4-GDI is overexpressed in some human breast cancer cell lines (Zhang, Y., and Zhang, B. (2006) Cancer Res. 66, 5592-5598). Here, we show that silencing of D4-GDI by RNA interference abrogates tumor growth and lung metastasis of otherwise highly invasive MDA-MB-231 breast cancer cells. Under anchorage-independent culture conditions, D4-GDI-depleted cells undergo rapid apoptosis (anoikis), which is known to hinder metastasis. We also found that D4-GDI associates with Rac1 and Rac3 in breast cancer cells, but not with other Rho GTPases tested (Cdc42, RhoA, RhoC, and TC10). Silencing of D4-GDI results in constitutive Rac1 activation and translocation from the cytosol to cellular membrane compartments and in sustained activation of p38 and JNK kinases. Rac1 blockade inhibits p38/JNK kinase activities and the spontaneous anoikis of D4-GDI knockdown cells. These results suggest that D4-GDI regulates cell function by interacting primarily with Rac GTPases and may play an integral role in breast cancer tumorigenesis. D4-GDI could prove to be a potential new target for therapeutic intervention.

MeSH terms

  • Animals
  • Anoikis
  • Apoptosis
  • Blotting, Western
  • Breast Neoplasms / metabolism*
  • Breast Neoplasms / pathology
  • Breast Neoplasms / prevention & control
  • Cell Adhesion
  • Cell Line, Tumor
  • Cell Movement
  • Cell Proliferation
  • Female
  • Gene Silencing / physiology*
  • Guanine Nucleotide Dissociation Inhibitors / genetics*
  • Humans
  • Immunoprecipitation
  • JNK Mitogen-Activated Protein Kinases / metabolism*
  • Lung Neoplasms / metabolism
  • Lung Neoplasms / prevention & control
  • Lung Neoplasms / secondary
  • Mice
  • Mice, Nude
  • Neoplasm Invasiveness
  • RNA, Small Interfering / pharmacology
  • Signal Transduction
  • Tumor Suppressor Proteins / genetics*
  • p38 Mitogen-Activated Protein Kinases / metabolism*
  • rac1 GTP-Binding Protein / genetics
  • rac1 GTP-Binding Protein / metabolism*
  • rho Guanine Nucleotide Dissociation Inhibitor beta
  • rho-Specific Guanine Nucleotide Dissociation Inhibitors

Substances

  • ARHGDIB protein, human
  • Guanine Nucleotide Dissociation Inhibitors
  • RAC1 protein, human
  • RNA, Small Interfering
  • Tumor Suppressor Proteins
  • rho Guanine Nucleotide Dissociation Inhibitor beta
  • rho-Specific Guanine Nucleotide Dissociation Inhibitors
  • JNK Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • rac1 GTP-Binding Protein