Abstract
Cell migration is a prerequisite for cancer invasion and metastasis, suggesting cell motility as a potential therapeutic target for cancer treatment. A synthetic library was screened to identify inhibitors of tumor cell migration. From this, we discovered that CAC-1098 (aurintricarboxylic acid) and CBI-0997 (5-(2,4-dimethoxy-5-ethylphenyl)-4-(4-bromophenyl) isoxazole) inhibited migration of MDA-MB-231 cells with IC50 = 5 and 50 nM, respectively. We synthesized KRIBB3 (5-(5-ethyl-2-hydroxy-4-methoxyphenyl)-4-(4-methoxyphenyl) isoxazole) by replacing the bromide group of CBI-0997 with a methoxyl group. Like CBI-0997, KRIBB3 has anti-migratory and anti-invasive activities in MDA-MB-231 cells. Because KRIBB3 has a better drug-like structure, we focused our effort on further understanding its anti-migratory mechanism. Biotinyl-KRIBB3 was synthesized as an affinity probe for identification of KRIBB3-binding proteins. Using affinity chromatography, we identified Hsp27 as a target protein of KRIBB3 in vitro. Treatment of MDA-MB-231 cells with phorbol 12-myristate 13-acetate induced protein kinase C-dependent phosphorylation of Hsp27 and tumor cell migration. In contrast, treatment of MDA-MB-231 cells with KRIBB3 blocked phorbol 12-myristate 13-acetate-induced phosphorylation of Hsp27 and tumor cell migration. Furthermore, overexpression of Hsp27 antagonized the inhibitory effect of KRIBB3 on tumor cell invasion, and knockdown of Hsp27 using small interfering RNA inhibited tumor cell migration. Overall, our results demonstrate that KRIBB3 inhibits tumor cell migration and invasion by blocking protein kinase C-dependent phosphorylation of Hsp27 through its direct binding to Hsp27.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Anisoles / chemistry
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Anisoles / pharmacology*
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Antineoplastic Agents / pharmacology*
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Blotting, Western
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Bromides / chemistry
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Cell Line, Tumor
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Cell Membrane / metabolism
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Cell Movement
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Chromatography, Affinity
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Crk-Associated Substrate Protein / metabolism
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DNA, Complementary / metabolism
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Dose-Response Relationship, Drug
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Drug Screening Assays, Antitumor*
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Enzyme Activation
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Enzyme Inhibitors / pharmacology
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Focal Adhesion Protein-Tyrosine Kinases / metabolism
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HSP27 Heat-Shock Proteins
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Heat-Shock Proteins / antagonists & inhibitors*
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Humans
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Inhibitory Concentration 50
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Intracellular Signaling Peptides and Proteins
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Isoxazoles / chemistry
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Isoxazoles / pharmacology*
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Models, Chemical
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Molecular Chaperones
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Molecular Sequence Data
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Neoplasm Invasiveness
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Neoplasm Proteins / antagonists & inhibitors*
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Neoplasms / drug therapy*
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Neoplasms / metabolism
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Phosphatidylinositol 3-Kinases / metabolism
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Phosphorylation
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Protein Binding
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Protein Kinase C / metabolism
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Protein Serine-Threonine Kinases / metabolism
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Protein Structure, Tertiary
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RNA, Small Interfering / chemistry
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RNA, Small Interfering / metabolism
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Time Factors
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Transfection
Substances
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5-(5-ethyl-2-hydroxy-4-methoxyphenyl)-4-(4-methoxyphenyl)isoxazole
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Anisoles
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Antineoplastic Agents
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Bromides
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Crk-Associated Substrate Protein
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DNA, Complementary
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Enzyme Inhibitors
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HSP27 Heat-Shock Proteins
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HSPB1 protein, human
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Heat-Shock Proteins
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Intracellular Signaling Peptides and Proteins
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Isoxazoles
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Molecular Chaperones
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Neoplasm Proteins
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RNA, Small Interfering
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MAP-kinase-activated kinase 2
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Focal Adhesion Protein-Tyrosine Kinases
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Protein Serine-Threonine Kinases
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Protein Kinase C