title: RhoC Is an Unexpected Target of RhoGDI2 in Prevention of Lung Colonization of Bladder Cancer.
abstract: RhoGDI2 (ARHGDIB) suppresses metastasis in a variety of cancers but the mechanism is unclear, thus hampering development of human therapeutics. RhoGDI2 is a guanine nucleotide dissociation inhibitor (GDI) for the Rho family of GTPases thought to primarily bind to Rac1; however, Rac1 activation was not decreased by RhoGDI2 expression in bladder cancer cells. To better understand the GTPase-binding partners for RhoGDI2, a mass spectrometry-based proteomic approach was used in bladder cancer cells. As expected, endogenous RhoGDI2 coimmunoprecipitates with Rac1 and unexpectedly also with RhoC. Further analysis demonstrated that RhoGDI2 negatively regulates RhoC, as knockdown of RhoGDI2 increased RhoC activation in response to serum stimulation. Conversely, overexpression of RhoGDI2 decreased RhoC activation. RhoC promoted bladder cancer cell growth and invasion, as knockdown increased cell doubling time, decreased invasion through Matrigel, and decreased colony formation in soft agar. Importantly, RhoC knockdown reduced in vivo lung colonization by bladder cancer cells following tail vein injection in immunocompromised mice. Finally, unbiased transcriptome analysis revealed a set of genes regulated by RhoGDI2 overexpression and RhoC knockdown in bladder cancer cells.
  
  
  CONCLUSIONS
  RhoGDI2 suppresses bladder cancer metastatic colonization via negative regulation of RhoC activity, providing a rationale for the development of therapeutics that target RhoC signaling.
authors.affiliation: Center for Cell Signaling and Department of Microbiology, Immunology and Cancer Biology University of Virginia, Charlottesville, Virginia.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Griner
authors.affiliation: Department of Mathematics and Computer Science, Eastern Connecticut State University, Willimantic, Connecticut.
authors.forename: Garrett M
authors.initials: GM
authors.lastname: Dancik
authors.affiliation: Department of Surgery and Pharmacology University of Colorado, Aurora, Colorado.
authors.forename: James C
authors.initials: JC
authors.lastname: Costello
authors.affiliation: Department of Surgery and Pharmacology University of Colorado, Aurora, Colorado.
authors.forename: Charles
authors.initials: C
authors.lastname: Owens
authors.affiliation: Department of Surgery and Pharmacology University of Colorado, Aurora, Colorado.
authors.forename: Sunny
authors.initials: S
authors.lastname: Guin
authors.affiliation: Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado, Aurora, Colorado.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Edwards
authors.affiliation: Center for Cell Signaling and Department of Microbiology, Immunology and Cancer Biology University of Virginia, Charlottesville, Virginia.
authors.forename: David L
authors.initials: DL
authors.lastname: Brautigan
authors.affiliation: Department of Surgery and Pharmacology University of Colorado, Aurora, Colorado. University of Colorado Comprehensive Cancer Center, Aurora, Colorado. dan.theodorescu@ucdenver.edu.
authors.forename: Dan
authors.initials: D
authors.lastname: Theodorescu
mesh_terms: D000818:Animals; D002465:Cell Movement; D049109:Cell Proliferation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism* / Q000556:secondary*; D051379:Mice; D009368:Neoplasm Transplantation; D040901:Proteomics; D001749:Urinary Bladder Neoplasms / Q000378:metabolism* / Q000473:pathology; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta / Q000378:metabolism*; D000075024:rhoC GTP-Binding Protein
chemical_list: C569658:ARHGDIB protein, human; C107953:RAC1 protein, human; D062949:rho Guanine Nucleotide Dissociation Inhibitor beta; C066690:RHOC protein, human; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D000075024:rhoC GTP-Binding Protein