Abstract
p21-Activated kinases (PAKs) are regulators of cell motility and proliferation. PAK activity is regulated in part by phosphoinositide-dependent kinase 1 (PDK1). We hypothesized that reduced PAK activity was involved in the effects of 2-amino-N-{4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-phenyl} acetamide (OSU-03012), a previously characterized PDK1 inhibitor derived from celecoxib. In three human thyroid cancer cell lines, OSU-03012 inhibited cell proliferation with reduced AKT phosphorylation by PDK1. OSU-03012 unexpectedly inhibited PAK phosphorylation at lower concentrations than PDK1-dependent AKT phosphorylation in two of the three lines. In cell-free kinase assays, OSU-03012 was shown to inhibit PAK activity and compete with ATP binding. In addition, computer modeling predicted a docking site for OSU-03012 in the ATP binding motif of PAK1. Finally, overexpression of constitutively activated PAK1 partially rescued the ability of motile NPA thyroid cancer cells to migrate during OSU-03012 treatment, suggesting that inhibition of PAK may be involved in the cellular effects of OSU-03012 in these cells. In summary, OSU-03012 is a direct inhibitor of PAK, and inhibition of PAK, either directly or indirectly, may be involved in its biological effects in vitro.
Footnotes
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This work was supported by grants from the National Cancer Institute (R-01-CA102572-02 and R21-01-CA111461-01) to M.D.R.
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Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
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doi:10.1124/mol.107.037556.
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ABBREVIATIONS: PDK1, phosphoinositide-dependent kinase 1; PAK, p21-activated kinase; EMT, epithelial-to-mesenchymal transition; MBP, myelin basic protein; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide; PARP, poly(ADP-ribose) polymerase; CA-PAK, constitutively active p21-activated kinase; FBS, fetal bovine serum; ELISA, enzyme-linked immunosorbent assay; PI3, phosphatidylinositol-3; DMSO, dimethyl sulfoxide; LY294002, 2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride; OSU-03012, 2-amino-N-{4-[5-(2-phenanthrenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-phenyl} acetamide; OSU-03013, 4-[5-(2-phenantrinenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl]-phenyl-guanidine.
- Received April 27, 2007.
- Accepted August 2, 2007.
- The American Society for Pharmacology and Experimental Therapeutics
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