Abstract
Vandetanib is a multitargeted tyrosine kinase inhibitor. Our initial studies demonstrated that this agent blocks vascular endothelial growth factor receptor, epidermal growth factor receptor, and platelet-derived growth factor receptor phosphorylation and mitogen-activated protein kinase (MAPK)-mediated signaling in glioma cell lines in a dose-dependent manner. Despite these effects, we observed that vandetanib had little effect on apoptosis induction at clinically achievable concentrations. Because histone deacetylase inhibitors (HDACIs) have been suggested to regulate signaling protein transcription and downstream interactions via modulation of protein chaperone function through the 90-kDa heat shock protein, we investigated whether combining vandetanib with an HDACI could synergistically potentiate signaling pathway inhibition and apoptosis induction in a panel of malignant human glioma cell lines. Proliferation assays, apoptosis induction studies, and Western immunoblot analysis were conducted in cells treated with vandetanib and HDACIs as single agents or in combination. Vandetanib and suberoylanalide hydroxamic acid reduced proliferation in all cell lines when used as single agents, and the combination produced marked potentiation of growth inhibition as assessed by combinatorial methods. These effects were paralleled by potentiation of Akt signaling inhibition and apoptosis induction. Our results indicate that inhibition of histone deacetylation enhances the antiproliferative effect of vandetanib in malignant human glioma cell lines by enhancing inhibition of MAPK, Akt, and other downstream effectors that may have application in combinatorial therapeutics for these tumors.
- GBM, glioblastoma multiforme
- MAPK, mitogen-activated protein kinase
- ERK, extracellular signal-regulated kinase
- EGF, epidermal growth factor
- EGFR, epidermal growth factor receptor
- PDGF, platelet derived growth factor
- PDGFR, platelet-derived growth factor receptor
- VEGF, vascular endothelial growth factor
- VEGFR, vascular endothelial growth factor receptor
- DMSO, dimethyl sulfoxide
- HDAC, histone deacetylase
- HDACI, histone deacetylase inhibitor
- HSP90, 90-kDa heat shock protein
- MOI, multiplicity of infection
- MTS, 3-[4,5-dimethylthiazol- 2yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H, tetrazolium
- PAGE, polyacrylamide gel electrophoresis
- PARP, poly(ADP-ribose) polymerase
- PTEN, phosphatase and tensin homolog
- TBS, Tris-buffered saline
- RTK, receptor tyrosine kinase
- CDK, cyclin-dependent kinase
- PI3K, phosphatidylinositol 3-kinase
- E-64, N-(trans-epoxysuccinyl)-l-leucine 4-guanidinobutylamide
- SAHA, suberoylanalide hydroxamic acid
- TSA, trichostatin A
- LY294002, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
- U0126, 1,4-diamino-2,3-dicyano-1,4-bis(methylthio)butadiene
- RET, “rearranged during transfection” oncogene
Footnotes
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This work was supported by the National Institutes of Health [Grant P01-NS40923].
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ZACTIMA is a registered trademark of the AstraZeneca group of companies.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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ABBREVIATIONS:
- Received May 5, 2009.
- Accepted July 17, 2009.
- © 2009 by The American Society for Pharmacology and Experimental Therapeutics
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