Abstract
Src is a non-receptor protein tyrosine kinase, the expression and activity of which is increased in >80% of human colon cancers with respect to normal colonic epithelium. Previous studies from this and other laboratories have demonstrated that Src activity contributes to tumorigenicity of established colon adenocarcinoma cell lines. Src participates in the regulation of many signal transduction pathways, among which are those leading to cellular survival. In this study, we addressed the potential role of Src activation to a specific aspect of tumor cell survival, resistance to detachment-induced apoptosis (anoikis). Using five colon tumor cell lines with different biologic properties and genetic alterations, we demonstrate that expression and activity of Src corresponds with resistance to anoikis. Enforced expression of activated Src in subclones of SW480 cells (of low intrinsic Src expression and activity) increases resistance to anoikis; whereas decreased Src expression in HT29 cells (of high Src expression and activity) by transfection with anti-sense Src expression vectors increases susceptibility to anoikis. In contrast, increasing or decreasing Src expression had no effect on susceptibility to staurosporine-induced apoptosis in attached cells. PD173955, a Src family-specific tyrosine kinase inhibitor, increases the susceptibility of HT29 cells to anoikis in a dose- and time-dependent manner. Increasing Src expression and activity led to increased phosphorylation of Akt, a mediator of cellular survival pathways, whereas decreasing Src activity led to decreased Akt phosphorylation. In colon tumor cells with high Src activity, the PI3 kinase inhibitor LY 294002 sensitized cells to anoikis. These results suggest that Src activation may contribute to colon tumor progression and metastasis in part by activating Akt-mediated survival pathways that decrease sensitivity of detached cells to anoikis.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Adenocarcinoma / enzymology
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Adenocarcinoma / genetics
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Adenocarcinoma / pathology*
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Amino Acid Substitution
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Anoikis / physiology*
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Apoptosis / drug effects
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Caspase 3
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Caspases / metabolism
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Cell Adhesion
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Cell Cycle
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Chromones / pharmacology
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Colonic Neoplasms / enzymology
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Colonic Neoplasms / genetics
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Colonic Neoplasms / pathology*
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Disease Progression
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Enzyme Activation / drug effects
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Enzyme Inhibitors / pharmacology
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Gene Expression Regulation, Neoplastic
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Genes, src
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Humans
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Morpholines / pharmacology
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Mutation, Missense
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Neoplasm Metastasis
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Neoplasm Proteins / antagonists & inhibitors
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Neoplasm Proteins / genetics
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Neoplasm Proteins / physiology*
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Phosphatidylinositol 3-Kinases / physiology
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Phosphoinositide-3 Kinase Inhibitors
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Phosphorylation / drug effects
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Protein Processing, Post-Translational / drug effects
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Protein Processing, Post-Translational / physiology
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Protein Serine-Threonine Kinases*
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Proto-Oncogene Proteins / physiology*
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Proto-Oncogene Proteins c-akt
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Proto-Oncogene Proteins c-bcl-2 / biosynthesis
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Proto-Oncogene Proteins c-bcl-2 / genetics
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Proto-Oncogene Proteins pp60(c-src) / antagonists & inhibitors
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Proto-Oncogene Proteins pp60(c-src) / physiology*
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Pyridones / pharmacology
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Pyrimidines / pharmacology
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Recombinant Fusion Proteins / physiology
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Signal Transduction / physiology*
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Staurosporine / pharmacology
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Transfection
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Tumor Cells, Cultured / metabolism
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Tumor Cells, Cultured / pathology
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bcl-X Protein
Substances
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BCL2L1 protein, human
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Chromones
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Enzyme Inhibitors
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Morpholines
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Neoplasm Proteins
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PD 173955
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Phosphoinositide-3 Kinase Inhibitors
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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Pyridones
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Pyrimidines
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Recombinant Fusion Proteins
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bcl-X Protein
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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Proto-Oncogene Proteins pp60(c-src)
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AKT1 protein, human
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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CASP3 protein, human
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Caspase 3
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Caspases
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Staurosporine