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J. Biol. Chem., Vol. 283, Issue 20, 13934-13942, May 16, 2008

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Activation of KLF8 Transcription by Focal Adhesion Kinase in Human Ovarian Epithelial and Cancer Cells^*

Xianhui Wang, Alison M. Urvalek, Jinsong Liu, and Jihe Zhao¹

From the Center for Cell Biology and Cancer Research, Albany Medical College, Albany, New York 12208 and the Department of Pathology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030

KLF8 (Krüppel-like factor 8) is a transcription factor downstream of focal adhesion kinase (FAK) important in the regulation of the cell cycle and also plays a critical role in oncogenic transformation and epithelial to mesenchymal transition. Here we report the mechanisms by which FAK regulates KLF8 expression in human ovarian epithelial and cancer cells. We show that the overexpression of both KLF8 and FAK in the human ovarian cancer cells as compared with the normal human ovarian surface epithelial cells is critical for cell growth. Using promoter luciferase reporter assays, we demonstrate that exogenous FAK strongly promotes the activity of the KLF8 promoter, and knockdown of FAK inhibits it. KLF8 promoter activity and mRNA levels are induced by expression of constitutively active (CA) phosphatidylinositol 3-kinase (PI3K) or CA-Akt but are repressed by dominant negative Akt or the PI3K inhibitor LY294002. Disruption of an Sp1 binding site in the KLF8 promoter abolishes the FAK- or Sp1-mediated promoter activation. Sp1 knockdown prevents the KLF8 promoter from being activated by Sp1 or CA-Akt, and expression of CA-Akt enhances Sp1 expression in SKOV3ip1 cells. Chromatin immunoprecipitation and oligonucleotide precipitation results show that Sp1 binds to the KLF8 promoter. Taken together, our data suggest that FAK induces KLF8 expression in human ovarian cancer cells by activating the PI3K-Akt signaling pathway, leading to the activation of KLF8 promoter by Sp1.

Received for publication, November 13, 2007 , and in revised form, March 18, 2008.

^* This work was supported by American Cancer Society Grant RSG CCG-111381 (to J. Z.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: MS338, Center for Cell Biology and Cancer Research, Albany Medical College, 47 New Scotland Ave., MC-165, Albany, NY 12208. Tel.: 518-262-2305; Fax: 518-262-5669; E-mail: zhaojh{at}mail.amc.edu.

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