title: The tumor-suppressor gene ARHI (DIRAS3) suppresses ovarian cancer cell migration through inhibition of the Stat3 and FAK/Rho signaling pathways.
abstract: Ovarian cancers migrate and metastasize over the surface of the peritoneal cavity. Consequently, dysregulation of mechanisms that limit cell migration may be particularly important in the pathogenesis of the disease. ARHI is an imprinted tumor-suppressor gene that is downregulated in >60% of ovarian cancers, and its loss is associated with decreased progression-free survival. ARHI encodes a 26-kDa GTPase with homology to Ras. In contrast to Ras, ARHI inhibits cell growth, but whether it also regulates cell motility has not been studied previously. Here we report that re-expression of ARHI decreases the motility of IL-6- and epidermal growth factor (EGF)-stimulated SKOv3 and Hey ovarian cancer cells, inhibiting both chemotaxis and haptotaxis. ARHI binds to and sequesters Stat3 in the cytoplasm, preventing its translocation to the nucleus and localization in focal adhesion complexes. Stat3 siRNA or the JAK2 inhibitor AG490 produced similar inhibition of motility. However, the combination of ARHI expression with Stat3 knockdown or inhibition produced greatest inhibition in ovarian cancer cell migration, consistent with Stat3-dependent and Stat3-independent mechanisms. Consistent with two distinct signaling pathways, knockdown of Stat3 selectively inhibited IL-6-stimulated migration, whereas knockdown of focal adhesion kinase (FAK) preferentially inhibited EGF-stimulated migration. In EGF-stimulated ovarian cancer cells, re-expression of ARHI inhibited FAK(Y397) and Src(Y416) phosphorylation, disrupted focal adhesions, and blocked FAK-mediated RhoA signaling, resulting in decreased levels of GTP-RhoA. Re-expression of ARHI also disrupted the formation of actin stress fibers in a FAK- and RhoA-dependent manner. Thus, ARHI has a critical and previously uncharacterized role in the regulation of ovarian cancer cell migration, exerting inhibitory effects on two distinct signaling pathways.
authors.affiliation: Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: D B
authors.initials: DB
authors.lastname: Badgwell
authors.forename: Z
authors.initials: Z
authors.lastname: Lu
authors.forename: K
authors.initials: K
authors.lastname: Le
authors.forename: F
authors.initials: F
authors.lastname: Gao
authors.forename: M
authors.initials: M
authors.lastname: Yang
authors.forename: G K
authors.initials: GK
authors.lastname: Suh
authors.forename: J-J
authors.initials: JJ
authors.lastname: Bao
authors.forename: P
authors.initials: P
authors.lastname: Das
authors.forename: M
authors.initials: M
authors.lastname: Andreeff
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.forename: Y
authors.initials: Y
authors.lastname: Yu
authors.forename: A A
authors.initials: AA
authors.lastname: Ahmed
authors.forename: W
authors.initials: W
authors.lastname: S-L Liao
authors.forename: R C
authors.initials: RC
authors.lastname: Bast
mesh_terms: D045744:Cell Line, Tumor; D002465:Cell Movement; D005260:Female; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D022001:Focal Adhesions; D016147:Genes, Tumor Suppressor / Q000502:physiology*; D006801:Humans; D053614:Janus Kinase 2 / Q000502:physiology; D010051:Ovarian Neoplasms / Q000235:genetics* / Q000473:pathology; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000235:genetics*; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: C117386:DIRAS3 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C066737:RHOA protein, human; D051416:Focal Adhesion Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein