title: Silencing of D4-GDI inhibits growth and invasive behavior in MDA-MB-231 cells by activation of Rac-dependent p38 and JNK signaling.
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.
authors.affiliation: Division of Therapeutic Proteins, Office of Biotechnology Products, Center for Drug Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Leslie A
authors.initials: LA
authors.lastname: Rivera Rosado
authors.forename: Sun Young
authors.initials: SY
authors.lastname: Moon
authors.forename: Baolin
authors.initials: B
authors.lastname: Zhang
mesh_terms: D000818:Animals; D023102:Anoikis; D017209:Apoptosis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D005260:Female; D020868:Gene Silencing / Q000502:physiology*; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000235:genetics*; D006801:Humans; D047468:Immunoprecipitation; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008175:Lung Neoplasms / Q000378:metabolism / Q000517:prevention & control / Q000556:secondary; D051379:Mice; D008819:Mice, Nude; D009361:Neoplasm Invasiveness; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins / Q000235:genetics*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: C569658:ARHGDIB protein, human; D020730:Guanine Nucleotide Dissociation Inhibitors; C107953:RAC1 protein, human; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein