(MMP) Activation and MMP-dependent Invasion in Ovarian Lysophosphatidic Acid Promotes Matrix Metalloproteinase

Ovarian cancer is an highly metastatic disease characterized by ascites formation and diffuse i.p. adhesion, invasion, and metastasis. Levels of lysophosphatidic acid (LPA) are elevated in the plasma of patients with ovarian carcinoma, including 90% of patients with stage I disease, suggesting that LPA may promote early events in ovarian carcinoma dissemination. Expression of matrix metalloproteinases (MMPs) is also upregulated in ovarian cancer tissues and ascites, and numerous studies have provided evidence for a direct role of MMPs in i.p. invasion and metastasis. Using three-dimensional type I collagen cultures or immobilized b1 integrin subunit-specific antibodies, we previously demonstrated that b1 integrin clustering promotes activation of proMMP-2 and processing of membrane type 1 MMP in ovarian cancer cells (S. M. Ellerbroek et al., Cancer Res., 59: 1635–1641, 1999). In the current study, the effect of LPA on MMP expression and invasive activity was investigated. Treatment of ovarian cancer cells with pathophysiological levels of LPA increased cellular adhesion to type I collagen and b1 integrin expression. A significant up-regulation of MMP-dependent proMMP-2 activation was observed in LPA-treated cells, leading to enhanced pericellular MMP activity. As a result of increased MMP activity, haptotactic and chemotactic motility, in vitro wound closure, and invasion of a synthetic basement membrane were enhanced. These data indicate that LPA contributes to metastatic dissemination of ovarian cancer cells via up-regulation of MMP activity and subsequent downstream changes in MMP-dependent migratory and invasive behavior.