Membrane-Type-3 Matrix Metalloproteinase (MT3-MMP) Functions as a Matrix Composition-Dependent Effector of Melanoma Cell Invasion Olga Tatti1,2, Mariliina Arjama1,2, Annamari Ranki3, Stephen J. Weiss4, Jorma Keski-Oja1,2, Kaisa Lehti1,2,5* 1 Research Programs Unit, Molecular Cancer Biology, University of Helsinki, Helsinki, Finland, 2 Departments of Pathology and Virology, Haartman Institute, Helsinki University Central Hospital, Helsinki, Finland, 3 Department of Dermatology and Allergology, Skin and Allergy Hospital, Helsinki University Central Hospital, Helsinki, Finland, 4 Division of Molecular Medicine and Genetics, Life Sciences Institute, University of Michigan, Ann Arbor, Michigan, United States of America, 5 Research Programs Unit, Genome-Scale Biology, Biomedicum Helsinki, University of Helsinki, Helsinki, Finland Abstract In primary human melanoma, the membrane-type matrix metalloproteinase, MT3-MMP, is overexpressed in the most aggressive nodular-type tumors. Unlike MT1-MMP and MT2-MMP, which promote cell invasion through basement membranes and collagen type I-rich tissues, the function of MT3-MMP in tumor progression remains unclear. Here, we demonstrate that MT3-MMP inhibits MT1-MMP-driven melanoma cell invasion in three-dimensional collagen, while yielding an altered, yet MT1-MMP-dependent, form of expansive growth behavior that phenocopies the formation of nodular cell colonies. In melanoma cell lines originating from advanced primary or metastatic lesions, endogenous MT3-MMP expression was associated with limited collagen-invasive potential. In the cell lines with highest MT3-MMP expression relative to MT1- MMP, collagen-invasive activity was increased following stable MT3-MMP gene silencing. Consistently, MT3-MMP overexpression in cells derived from less advanced superficially spreading melanoma lesions, or in the MT3-MMP knockdown cells, reduced MT1-MMP-dependent collagen invasion. Rather than altering MT1-MMP transcription, MT3-MMP interacted with MT1-MMP in membrane complexes and reduced its cell surface expression. By contrast, as a potent fibrinolytic enzyme, MT3-MMP induced efficient invasion of the cells in fibrin, a provisional matrix component frequently found at tumor-host tissue interfaces and perivascular spaces of melanoma. Since MT3-MMP was significantly upregulated in biopsies of human melanoma metastases, these results identify MT3-MMP as a matrix-dependent modifier of the invasive tumor cell functions during melanoma progression. Citation: Tatti O, Arjama M, Ranki A, Weiss SJ, Keski-Oja J, et al. (2011) Membrane-Type-3 Matrix Metalloproteinase (MT3-MMP) Functions as a Matrix Composition-Dependent Effector of Melanoma Cell Invasion. PLoS ONE 6(12): e28325. doi:10.1371/journal.pone.0028325 Editor: Zhongjun Zhou, The University of Hong Kong, Hong Kong Received June 19, 2011; Accepted November 5, 2011; Published December 2, 2011 Copyright: 2011 Tatti 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 work was supported by the Academy of Finland (J.K.-O., K.L.), University of Helsinki Foundations (K.L., O.T.), Finnish Cancer Foundation (J.K.-O., K.L.), Finnish Cancer Institute (K.L.), Sigrid Juselius Foundation (J.K.-O., K.L.), Helsinki Univ. Hospital Fund (J.K.-O.), Magnus Ehrnrooth Foundation (K.L.), Biocentrum Helsinki (J.K.-O.), Helsinki Biomedical Graduate School (O.T., M.A.), and Emil Aaltonen Foundation (O.T.). 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: kaisa.lehti@helsinki.fi Introduction Cancer-related mortality is generally associated with the development of metastatic lesions. During the progression to metastatic cancer, tumor cells invade through extracellular matrix (ECM) barriers such as the basement membrane and interstitial stroma, enter vascular or lymphatic vessels, extravasate, and colonize distant organs [1,2]. Comparisons between the gene expression profiles of non-metastatic and metastatic cancers have revealed distinct genetic footprints for each disease state [3]. In such analyses, the proteolytic enzyme, membrane-type matrix metalloproteinase 1 (MT1-MMP, MMP14), is often linked to the metastatic disease [4,5] with the protease upregulated in tumor cells as well as surrounding stromal cells [6–9]. The strongest MT1-MMP induction often correlates with the transition of tumor cells to a rapidly invasive mesenchymal phenotype [10], and its elevated expression in cancer tissues correlates frequently with disease aggressiveness and poor prognosis [5,7]. The MT-MMP family comprises six members, MT(1–6)- MMPs. Each of the proteases have been implicated in tumor progression, although their expression pattern and known functions appear distinct [11–14]. MT1- and MT2-MMP (MMP15) can each drive tumor cell invasion through basement membranes and the collagen type I-rich interstitial stroma [10,15], while MT3-MMP (MMP16) cannot efficiently cleave native collagen type I or confer cells with collagen-invasive ability in vitro or in vivo [15–17]. However, when overexpressed, both MT1- and MT3-MMP mediate cell invasion in cross-linked fibrin gel, a provisional form of extracellular matrix commonly deposited within tumor tissues and perivascular spaces in vivo [18]. Unlike wide MT1-MMP expression in different cancers, notable MT3-MMP mRNA levels have been detected in relatively few types of cancer, such as gliomas, hepatocellular carcinoma, gastric cancer and melanoma, where its translation efficiency, protein expression and function remain poorly defined [11,19–22]. PLoS ONE | www.plosone.org 1 December 2011 | Volume 6 | Issue 12 | e28325