title: DLC1 negatively regulates angiogenesis in a paracrine fashion.
abstract: The Rho GTPase-activating protein DLC1 is a tumor suppressor that is often deleted in liver cancer and downregulated in other cancers. DLC1 regulates the actin cytoskeleton, cell shape, adhesion, migration, and proliferation through its Rho GTPase-activating protein activity and focal adhesion localization. In this study, we silenced DLC1 in nonmalignant prostate epithelial cells to explore its tumor suppression functions. Small hairpin RNA-mediated silencing of DLC1 was insufficient to promote more aggressive phenotypes associated with tumor cell growth. In contrast, DLC1 silencing promoted pro-angiogenic responses through vascular endothelial growth factor (VEGF) upregulation, accompanied by the accumulation of hypoxia-inducible factor 1α and its nuclear localization. Notably, modulation of VEGF expression by DLC1 was dependent on epidermal growth factor receptor-MAP/ERK kinase-hypoxia-inducible factor 1 signaling but on RhoA pathways. Clinically, VEGF upregulation is a highly significant event in prostate cancers in which DLC1 is downregulated. Thus, our results strongly suggest that loss of DLC1 may serve as a "second hit" in promoting angiogenesis in a paracrine fashion during tumorigenesis.
authors.affiliation: Department of Biochemistry and Molecular Medicine, Center for Tissue Regeneration and Repair, University of California-Davis, Sacramento, California 95817, USA.
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Shih
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Liao
authors.forename: Yuan
authors.initials: Y
authors.lastname: Lin
authors.forename: Su Hao
authors.initials: SH
authors.lastname: Lo
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism; D015153:Blotting, Western; D002448:Cell Adhesion; D002465:Cell Movement; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D020690:GTPase-Activating Proteins / Q000502:physiology*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D007124:Immunoenzyme Techniques; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D009389:Neovascularization, Pathologic / Q000378:metabolism* / Q000473:pathology; D019899:Paracrine Communication; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D046888:Tissue Array Analysis; D025521:Tumor Suppressor Proteins / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C112352:DLC1 protein, human; D020690:GTPase-Activating Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; D042461:Vascular Endothelial Growth Factor A; D020742:rhoA GTP-Binding Protein