Matrix metalloproteinase-2 Promotes avb3 Integrin- Mediated Adhesion and Migration of Human Melanoma Cells by Cleaving Fibronectin Yang Jiao, Xue Feng, Yinpeng Zhan, Ruifei Wang, Sheng Zheng, Wenguang Liu*, Xianlu Zeng* Institute of Genetics and Cytology, Northeast Normal University, Changchun, Jilin, China Abstract Background: Matrix metalloproteinase-2 (MMP-2) is a key regulator in the migration of tumor cells. avb3 integrin has been reported to play a critical role in cell adhesion and regulate the migration of tumor cells by promoting MMP-2 activation. However, little is known about the effects of MMP-2 on avb3 integrin activity and avb3 integrin-mediated adhesion and migration of tumor cells. Methodology/Principal Findings: Human melanoma cells were seeded using an agarose drop model and/or subjected to in vitro analysis using immunofluorescence, adhesion, migration and invasion assays to investigate the relationship between active MMP-2 and avb3 integrin during the adhesion and migration of the tumor cells. We found that MMP-2 was localized at the leading edge of spreading cells before avb3 integrin. avb3 integrin-mediated adhesion and migration of the tumor cells were inhibited by a MMP-2 inhibitor. MMP-2 cleaved fibronectin into small fragments, which promoted the adhesion and migration of the tumor cells. Conclusion/Significance: MMP-2 cleaves fibronectin into small fragments to enhance the adhesion and migration of human melanoma cells mediated by avb3 integrin. These results indicate that MMP-2 may guide the direction of the tumor cell migration. Citation: Jiao Y, Feng X, Zhan Y, Wang R, Zheng S, et al. (2012) Matrix metalloproteinase-2 Promotes avb3 Integrin-Mediated Adhesion and Migration of Human Melanoma Cells by Cleaving Fibronectin. PLoS ONE 7(7): e41591. doi:10.1371/journal.pone.0041591 Editor: F. Gisou van der Goot, Ecole Polytechnique Federale de Lausanne, Switzerland Received August 14, 2011; Accepted June 27, 2012; Published July 27, 2012 Copyright: 2012 Jiao et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was supported by grants from the National Nature Science Foundation of China (81071726, 81172014), the specialized Research Fund for the Doctoral Program of Higher education (20100043110007), and the Fundamental Research Funds for the Central Universities (10SSXT129). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: zengx779@nenu.edu.cn (XZ); liuwg788@nenu.edu.cn (WL) Introduction Tumor metastasis characterized by the dissemination of tumor cells from a primary site to the distant sites is the most frequent cause of death for cancer patients [1,2]. The initial step of tumor metastasis is a process of invasive tumor cell migrating in basement membrane, which implicates cell adhesion and migration as well as proteolysis of the extracellular matrix (ECM). This step involves many molecules including matrix metalloproteinases (MMPs) and integrins [3–16]. MMPs are a family of zinc-dependent matrix-degrading enzymes, which include collagenases, stromelysins, and gelati- nases. MMPs regulate various cell behaviors through their basic function in protein degradation [10–23]. The basement mem- brane, the first barrier for the invading epithelial tumor cells, is mainly composed of type IV collagen and fibronectin, which are degraded primarily by type IV collagenases and gelatinases[11– 15,20,22,24–26]. MMP-2 (72 kDa) and MMP-9 (92 kDa) are two gelatinases. Integrins are heterodimeric adhesion molecules, composed of noncovalently associated transmembrane glycoproteins a and b units, which connect adhesive proteins in the ECM to the intracellular actin cytoskeleton [27–33]. Integrins exist in different states of activation which determine the avidity and affinity of integrins to their ligands [4,30–34]. avb3 integrin is a receptor of proteins with an exposed Arg-Gly-Asp (RGD) tripeptide, including vitronectin, fibronectin, fibrinogen, thrombospondin, osteopontin, von Willebrand factor, and some degraded laminins and collagens [27,31,35,36]. Numerous studies have documented the marked differences in the surface expression and distribution of integrins in malignant tumor cells [37]. avb3 integrin is expressed strongly on the surface of malignant melanoma cells and angiogenic blood vessels, but weakly on pre-neoplastic melanomas and quiescent blood vessels [30,38]. Furthermore, inducing the expression of the integrin subunit av or b3 increased the metastatic potential of a melanoma cell line [19,28,39,40]. MMP-2 directly binds to avb3 integrin, which is a regulator of MMP-2 activation during tumor cell migration [15,41–43]. However, whether MMP-2, in turn, contributes to avb3 integrin-mediated tumor cell migration is not clear. We examined the expression of MMP-2 and avb3 integrin in human A375 melanoma cells and human M21 melanoma cells using immuno- fluorescence staining, and demonstrated that MMP-2 accumulated at the leading edge of migrating cells before avb3 integrin. Given these findings, we addressed whether MMP-2 was an important PLoS ONE | www.plosone.org 1 July 2012 | Volume 7 | Issue 7 | e41591