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.
©2010 AACR.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Animals
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Aorta / cytology
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Aorta / metabolism
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Blotting, Western
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Cell Adhesion
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Cell Movement
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Cells, Cultured
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Enzyme-Linked Immunosorbent Assay
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GTPase-Activating Proteins / physiology*
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Humans
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Hypoxia-Inducible Factor 1, alpha Subunit / genetics
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Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
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Immunoenzyme Techniques
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Male
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Mice
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Mice, Inbred C57BL
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Mice, Nude
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Neovascularization, Pathologic / metabolism*
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Neovascularization, Pathologic / pathology
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Paracrine Communication*
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Prostatic Neoplasms / genetics
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Prostatic Neoplasms / metabolism*
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Prostatic Neoplasms / pathology
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RNA, Messenger / genetics
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RNA, Small Interfering / pharmacology
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Reverse Transcriptase Polymerase Chain Reaction
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Signal Transduction
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Tissue Array Analysis
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Tumor Suppressor Proteins / physiology*
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Vascular Endothelial Growth Factor A / genetics
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Vascular Endothelial Growth Factor A / metabolism
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Xenograft Model Antitumor Assays
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rhoA GTP-Binding Protein / genetics
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rhoA GTP-Binding Protein / metabolism
Substances
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DLC1 protein, human
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GTPase-Activating Proteins
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Hypoxia-Inducible Factor 1, alpha Subunit
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RNA, Messenger
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RNA, Small Interfering
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Tumor Suppressor Proteins
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Vascular Endothelial Growth Factor A
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rhoA GTP-Binding Protein