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Angiogenesis, Metastasis, and the Cellular Microenvironment

Lysophosphatidic Acid Down-Regulates Stress Fibers and Up-Regulates Pro–Matrix Metalloproteinase-2 Activation in Ovarian Cancer Cells

Departments of ¹ Obstetrics and Gynecology and ² Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois; ³ Laboratory of Pathology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland; ⁴ Office of the Director, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Bethesda, Maryland; and ⁵ Department of Obstetrics and Gynecology, Gynecologic Oncology, New York, New York

Requests for reprints: David A. Fishman, Gynecologic Oncology, Department of Obstetrics and Gynecology, 550 First Avenue, New York, NY 10016. E-mail: director-gynonc{at}med.nyu.edu

Epithelial ovarian cancer (EOC) is asymptomatic at early stages and is often diagnosed late when tumor cells are highly metastatic. Lysophosphatidic acid (LPA) has been implicated in ovarian oncogenesis as levels of this lipid are elevated in patient ascites and plasma. Because the underlying mechanism governing LPA regulation of matrix metalloproteinase-2 (MMP-2) activation remains undefined, we investigated the relationship between LPA-induced changes in actin microfilament organization and MMP-2 enzymatic activity. We report that when cells were cultured at a high density, LPA mediated stress fiber and focal adhesion disassembly and significantly repressed RhoA activity in EOC cells. Inhibition of Rho-kinase/ROCK enhanced both LPA-stimulated loss of stress fibers and pro–MMP-2 activation. In contrast, expression of the constitutively active RhoA(G14V) mutant diminished LPA-induced pro–MMP-2 activation. LPA had no effects on membrane type 1–MMP or tissue inhibitor of metalloproteinase-2 expression, but up-regulated MMP-2 levels, contributing to the induction of MMP-2 activation. Interestingly, when cells were cultured at a low density, stress fibers were present after LPA stimulation, and ROCK activity was required for EOC cell migration. Collectively, these results were consistent with a model in which LPA stimulates the metastatic dissemination of EOC cells by initiating loss of adhesion and metalloproteinase activation. (Mol Cancer Res 2007;5(2):121–31)