Indole-3-carbinol inhibits MDA-MB-231 breast cancer cell motility and induces stress fibers and focal adhesion formation by activation of Rho kinase activity

Authors

  • Christine T. Brew,

    1. Department of Molecular and Cell Biology, The University of California at Berkeley, Berkeley, CA
    2. Cancer Research Laboratory, The University of California at Berkeley, Berkeley, CA
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  • Ida Aronchik,

    1. Department of Molecular and Cell Biology, The University of California at Berkeley, Berkeley, CA
    2. Cancer Research Laboratory, The University of California at Berkeley, Berkeley, CA
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  • Karena Kosco,

    1. Signal Transduction Program, The Burnham Institute, La Jolla, CA
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  • Jasmine McCammon,

    1. Department of Molecular and Cell Biology, The University of California at Berkeley, Berkeley, CA
    2. Cancer Research Laboratory, The University of California at Berkeley, Berkeley, CA
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  • Leonard F. Bjeldanes,

    1. Department of Nutritional Sciences and Toxicology, The University of California at Berkeley, Berkeley, CA
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  • Gary L. Firestone

    Corresponding author
    1. Department of Molecular and Cell Biology, The University of California at Berkeley, Berkeley, CA
    2. Cancer Research Laboratory, The University of California at Berkeley, Berkeley, CA
    • Department of Molecular and Cell Biology, 591 LSA, University of California at Berkeley, Berkeley, CA 94720-3200, USA
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    • Fax: +510-643-6791


Abstract

Indole-3-carbinol (I3C), a phytochemical derived from cruciferous vegetables such as broccoli and Brussels sprouts, has potent antiproliferative effects in human breast cancer cells and has been shown to decrease metastatic spread of tumors in experimental animals. Using chemotaxis and fluorescent-bead cell motility assays, we demonstrated that I3C significantly decreased the in vitro migration of MDA-MB-231 cells, a highly invasive breast cancer cell line. Immunofluorescence staining of the actin cytoskeleton revealed that concurrent with the loss of cell motility, I3C treatment significantly increased stress fiber formation. Furthermore, I3C induced the localization of the focal adhesion component vinculin and tyrosine-phosphorylated proteins to the cell periphery, which implicates an indole-dependent enhancement of focal adhesions within the outer boundary of the cells. Coimmunoprecipitation analysis of focal adhesion kinase demonstrated that I3C stimulated the dynamic formation of the focal adhesion protein complex without altering the total level of individual focal adhesion proteins. The RhoA-Rho kinase pathway is involved in stress fiber and focal adhesion formation, and I3C treatment stimulated Rho kinase enzymatic activity and cofilin phosphorylation, which is a downstream target of Rho kinase signaling, but did not increase the level of active GTP-bound RhoA. Exposure of MDA-MB-231 cells to the Rho kinase inhibitor Y-27632, or expression of dominant negative RhoA ablated the I3C induced formation of stress fibers and of peripheral focal adhesions. Expression of constitutively active RhoA mimicked the I3C effects on both processes. Taken together, our data demonstrate that I3C induces stress fibers and peripheral focal adhesions in a Rho kinase-dependent manner that leads to an inhibition of motility in human breast cancer cells. © 2008 Wiley-Liss, Inc.

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