Abstract
Metastasis contributes to the poor prognosis of hepatocellular carcinoma (HCC). Anoikis resistance and orientation chemotaxis are two important and sequential events in tumor cell metastasis. The process of tumor metastasis is known to be regulated by AEG-1, an important oncogene that plays a critical role in tumor metastasis, though the effects of this oncogene on anoikis resistance and orientation chemotaxis in HCC cells are currently unknown. To directly assess the role of AEG-1 in these processes, we up-regulated AEG-1 expression via exogenous transfection in SMMC-7721 cells, which express low endogenous levels of AEG-1; and down-regulated AEG-1 expression via siRNA-mediated knockdown in MHCC-97H and HCC-LM3 cells, which express high endogenous levels of AEG-1. Our data directly demonstrate that AEG-1 promotes cell growth as assessed by cell proliferation/viability and cell cycle analysis. Furthermore, the prevention of anoikis by AEG-1 correlates with decreased activation of caspase-3. AEG-1-dependent anoikis resistance is activated via the PI3K/Akt pathway and is characterized by the regulation of Bcl-2 and Bad. The PI3K inhibitor LY294002 reverses the AEG-1 dependent effects on Akt phosphorylation, Bcl-2 expression and anoikis resistance. AEG-1 also promotes orientation chemotaxis of suspension-cultured cells towards supernatant from Human Pulmonary Microvascular Endothelial Cells (HPMECs). Our results show that AEG-1 activates the expression of the metastasis-associated chemokine receptor CXCR4, and that its ligand, CXCL12, is secreted by HPMECs. Furthermore, the CXCR4 antoagonist AMD3100 decreases AEG-1-induced orientation chemotaxis. These results define a pathway by which AEG-1 regulates anoikis resistance and orientation chemotaxis during HCC cell metastasis.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Anoikis / drug effects*
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Benzylamines
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Cell Adhesion / drug effects
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Cell Adhesion Molecules / antagonists & inhibitors
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Cell Adhesion Molecules / genetics*
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Cell Adhesion Molecules / metabolism
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Cell Cycle / drug effects
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Cell Line, Tumor
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Cell Survival / drug effects
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Chemokine CXCL12 / antagonists & inhibitors
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Chemokine CXCL12 / genetics
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Chemokine CXCL12 / metabolism
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Chemotaxis / drug effects*
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Chromones / pharmacology
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Culture Media, Conditioned / pharmacology
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Cyclams
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Endothelial Cells / cytology
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Endothelial Cells / metabolism
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Gene Expression Regulation, Neoplastic*
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Hepatocytes / drug effects
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Hepatocytes / metabolism*
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Hepatocytes / pathology
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Heterocyclic Compounds / pharmacology
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Humans
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Membrane Proteins
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Morpholines / pharmacology
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Phosphatidylinositol 3-Kinases / genetics
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Phosphatidylinositol 3-Kinases / metabolism
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Phosphoinositide-3 Kinase Inhibitors
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Phosphorylation / drug effects
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Proto-Oncogene Proteins c-akt / genetics
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Proto-Oncogene Proteins c-akt / metabolism
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Proto-Oncogene Proteins c-bcl-2 / genetics
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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RNA-Binding Proteins
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Receptors, CXCR4 / genetics
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Receptors, CXCR4 / metabolism
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Signal Transduction
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bcl-Associated Death Protein / genetics
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bcl-Associated Death Protein / metabolism
Substances
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BAD protein, human
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BCL2 protein, human
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Benzylamines
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Cell Adhesion Molecules
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Chemokine CXCL12
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Chromones
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Culture Media, Conditioned
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Cyclams
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Heterocyclic Compounds
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MTDH protein, human
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Membrane Proteins
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Morpholines
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Phosphoinositide-3 Kinase Inhibitors
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Proto-Oncogene Proteins c-bcl-2
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RNA, Small Interfering
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RNA-Binding Proteins
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Receptors, CXCR4
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bcl-Associated Death Protein
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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Proto-Oncogene Proteins c-akt
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plerixafor
Grants and funding
This study was supported by the National Natural Science Foundation of China No.81270507, No.81372663 and No.81000159). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.