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

Thuy-Vy Do,Emanuel F Petricoin,David A Fishman,Lance A Liotta,David M Berman,Jay C Symowicz,M Sharon Stack

doi:10.1158/1541-7786.mcr-06-0319

Abstract

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.

Highlights

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy among women in the Western world
When EOC cells were plated at a low density, stress fibers were present in vehicle- and Lysophosphatidic acid (LPA)-treated cells (Fig. 1)
When EOC cells were plated at a high density, LPA exposure began to trigger the loss of stress fibers, as well as an increase in peripheral filaments when compared with vehicle-treated cells (Fig. 1)

Summary

Introduction

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy among women in the Western world. More than two-thirds of women are diagnosed during later stages when 5-year survival rates are only 20% to 30%. When ovarian cancer is diagnosed early, the longterm survival rate is almost 90% [1,2,3]. Lysophosphatidic acid (LPA) is a bioactive lipid that has been shown in preliminary studies to be a promising early diagnostic and prognostic biomarker for EOC [4, 5]. LPA exerts its effects upon binding to cognate G protein – coupled receptors encoded by the endothelial cell differentiation gene (Edg) family members. LPA elicits a diverse range of biological responses, including platelet aggregation, smooth muscle contraction, mitogenesis, and cell shape changes [6]

Methods

Results

Conclusion