Regulatory role of c-Met in insulin-like growth factor-I receptor–mediated migration and invasion of human pancreatic carcinoma cells Todd W. Bauer, 1 Ray J. Somcio, 2 Fan Fan, 2 Wenbiao Liu, 2 Marjorie Johnson, 2 Donald P. Lesslie, 2 Douglas B. Evans, 1 Gary E. Gallick, 2 and Lee M. Ellis 1,2 Departments of 1 Surgical Oncology and 2 Cancer Biology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas Abstract Pancreatic carcinoma cells overexpress the insulin-like growth factor-I (IGF-I) receptor (IGF-IR) and the hepato- cyte growth factor (HGF) receptor, c-Met, which are both known to mediate tumor cell migration and invasion. We hypothesized that IGF-IR and c-Met cooperate to induce migration and invasion of human pancreatic carcinoma cells and that IGF-I-mediated migration and invasion depend on c-Met. Migration and invasion assays were done with the human pancreatic cancer cell line L3.6pl treated with PBS, IGF-I, HGF, or IGF-I plus HGF. To determine if c-Met is necessary for IGF-IR-mediated migration and invasion, c-Met was down-regulated in L3.6pl cells via adenoviral infection with a c-Met ribozyme before IGF-I treatment. IGF-I and HGF increased cell migration and invasion. Furthermore, IGF-I plus HGF had a greater than additive effect on cell migration and invasion compared with either growth factor alone. Down-regulation of c-Met nearly completely inhibited IGF-I-mediated migration and invasion. Our findings suggest that IGF-IR and c-Met cooperate to induce migration and invasion of human pancreatic carcinoma cells. Furthermore, c-Met is required for both HGF- and IGF-I-mediated migration and invasion. Elucidation of the signaling pathways that contribute to tumor progression and metastasis should provide a foundation for the deve- lopment of targeted therapies for pancreatic carcinoma. [Mol Cancer Ther 2006;5(7):1676 –82] Introduction Pancreatic adenocarcinomas are highly aggressive tumors, and patients with this malignancy have a 5-year overall survival rate of only 4% (1). Even in patients with apparently localized, resectable disease, the 5-year overall survival rate is only 21% (2). More effective therapies for pancreatic carcinoma are thus needed. Insulin-like growth factor-I (IGF-I; refs. 3–13) and its receptor, IGF-I receptor (IGF-IR), and hepatocyte growth factor (HGF)/scatter factor (14–18) and its receptor, c-Met, have been implicated in the development and progression of a variety of human cancers, including pancreatic adenocarcinoma. IGF-I/IGF-IR signaling (19–23) and HGF/c-Met signaling (12, 18, 24–27) are important mediators of tumor cell migration and invasion. However, the pathways by which these factors induce tumor cell migration and invasion have not been fully elucidated. Cooperation between various receptors and their signaling pathways is important in regulating cellular responses. Examples include cooperation between the tyrosine kinase receptor Ron and the epidermal growth factor receptor (28), between IGF-IR and epidermal growth factor receptor (29), between the estrogen receptor and IGF-IR (30), and between G protein–coupled receptors and IGF-IR (31). Although cooperation between IGF-IR and c-Met in human pancreatic carcinoma cells has not been shown previously, evidence suggests that such cooperation is likely. First, IGF-I signaling in breast carcinoma (5, 20) and HGF signaling in various malignancies (24, 32, 33), including pancreatic carcinoma (12), result in activation of a common downstream mediator of invasion, the urokinase plasmin- ogen activator/urokinase plasminogen activator receptor system; urokinase plasminogen activator has been shown to cleave pro-HGF to active HGF (34). Second, IGF-I signaling induces hypoxia-inducible factor-1a in pancreatic carcinoma cells (11), and hypoxia, likely through this factor, has been shown to increase c-Met levels in human lung, hepatocellular, and other carcinomas (35). Third, growth factor receptor binding protein 2–associated binder-1, which is the main substrate and docking protein regulating downstream signaling by c-Met, has also been shown to function as a signaling intermediate for IGF-I (36). Fourth, IGF-I and HGF have been shown to function as comitogens in a rat hepatoma cell line (37). We therefore hypothesized that IGF-IR and c-Met cooperate to induce migration and invasion of human pancreatic carcinoma cells and that IGF-I-mediated migra- tion and invasion depend on c-Met. In the current study, we used a c-Met ribozyme to down-regulate c-Met function in L3.6pl human pancreatic carcinoma cells and then treated cells with PBS, IGF-I, HGF, or IGF-I plus HGF Received 6/2/05; revised 4/21/06; accepted 5/4/06. Grant support: NIH T32 grant CA-09599 (T.W. Bauer and D.P. Lesslie), NIH Cancer Center Support grant CA-16672, and Lockton Fund for Pancreatic Cancer Research grant (D.B. Evans, G.E. Gallick, and L.M. Ellis). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Requests for reprints: Lee M. Ellis, Department of Surgical Oncology, Unit 444, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030. Phone: 713-792-6926; Fax: 713-792-4689. E-mail: lellis@mdanderson.org Copyright C 2006 American Association for Cancer Research. doi:10.1158/1535-7163.MCT-05-0175 1676 Mol Cancer Ther 2006;5(7). July 2006 on May 14, 2016. © 2006 American Association for Cancer Research. mct.aacrjournals.org Downloaded from