Synergistic effects of epidermal growth factor and hepatocyte growth factor on human ovarian cancer cell invasion and migration: Role of extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase

Ovarian cancer is the primary cause of death from gynecological malignancies with a poor prognosis characterized by widespread peritoneal dissemination. However, mechanisms of invasion and metastasis in ovarian cancer remain poorly understood. Epidermal growth factor (EGF) and hepatocyte growth factor (HGF) are often both overexpressed and contribute to the growth of ovarian cancer by activating autocrine pathways. In the present study, we investigated the mechanisms of invasive activity of EGF, HGF, and their synergistic effects in human ovarian cancer cells. Here our data suggest that EGF and HGF may use unique and overlapping signaling cascades leading to the invasive phenotype. We revealed that HGF-mediated cell migration and invasion required the coordinate activation of the phosphatidylinositol 3-kinase/Akt and extracellular signal-regulated kinase 1/2. Although EGF-dependent invasive phenotype appeared to have similar requirements for phosphatidylinositol 3-kinase, this growth factor used the alternative p38MAPK pathway for cell invasion. A significant role of p38 MAPK was further supported by the observation that expression of dominant negative p38 MAPK likewise inhibited EGF-dependent invasiveness and cell motility. We also showed that EGF cooperated with HGF to promote a highly invasive phenotype via the increased secretion of matrix metalloproteinase (MMP)-9. The coincident induction of MMP-9 was functionally significant because inclusion of MMP-9 inhibitor or an anti-MMP-9 neutralizing antibody abolished EGF- and HGF-induced cellular invasion. These findings provide insights into the mechanism of the malignant progression of ovarian cancer.