Targeting of Breast Cancer through MT1-MMP/Tetraspanin Complexes W81XWH-08-1-0179

EWI-2, a cell surface IgSF protein, is highly expressed in normal human brain but is considerably diminished in glioblastoma tumors and cell lines. Moreover, loss of EWI-2 expression correlated with a shorter survival time in human glioma patients, suggesting that EWI-2 might be a natural inhibitor of glioblastoma. In support of this idea, EWI-2 expression significantly impaired both ectopic and orthotopic tumor growth in nude mice in vivo. In vitro assays provided clues regarding EWI-2 functions. Expression of EWI-2 in T98G and/or U87-MG malignant glioblastoma cell lines failed to alter two-dimensional cell proliferation but inhibited glioblastoma colony formation in soft agar and caused diminished cell motility and invasion. At the biochemical level, EWI-2 markedly affects the organization of four molecules (tetraspanin proteins CD9 and CD81 and matrix metalloproteinases MMP-2 and MT1MMP), which play key roles in the biology of astrocytes and gliomas. EWI-2 causes CD9 and CD81 to become more associated with each other, whereas CD81 and other tetraspanins become less associated with MMP-2 and MT1MMP. We propose that EWI-2 inhibition of glioblastoma growth in vivo is at least partly explained by the capability of EWI-2 to inhibit growth and/or invasion in vitro. Underlying these functional effects, EWI-2 causes a substantial molecular reorganization of multiple molecules (CD81, CD9, MMP-2, and MT1-MMP) known to affect proliferation and/ or invasion of astrocytes and/or glioblastomas. Neoplasia (2009) 11, 77–86 Introduction Malignant gliomas constitute most primary brain tumors. Along with high proliferative capacity, invasiveness, and resistance to conventional therapies, they are characterized by a progressive rise in the number and nature of cytogenetic aberrations [1]. For multiple reasons, we considered that EWI-2, a cell surface transmembrane protein in the immunoglobulin superfamily [2], might affect glioma tumor biology. First, mRNA for EWI-2 is more elevated in brain than in any other adult human tissue [2]. Second, EWI-2 affects the motility and morphology of multiple distinct tumor cell types [3–5]. Third, EWI-2 associates closely with two proteins (tetraspanins CD9 and CD81) that have previously been linked to astrocyte-astrocytoma tumor progression and/or proliferation. Whereas CD9 expression correlates with Abbreviations: EWI-2 and EWI-F, cell surface immunoglobulin superfamily proteins containing conserved “Glu-Trp-Ile”motifs;MT1-MMP,membrane type 1matrixmetalloproteinase; MMP-2, matrix metalloproteinase 2; TEM, tetraspanin-enriched microdomain Address all correspondence to: Martin E. Hemler, Dana-Farber Cancer Institute, Rm D1430, 44 Binney Street, Boston, MA 02115. E-mail: [email protected] This work was supported by grants from the National Institutes of Health (GM38903, CA42368) to M.E.H., Ruth L. Kirschstein National Research Service Award (T32) to T.V.K., Sidney Kimmel Foundation grant to A.L.K., Canadian Institutes of Health Research Fellowship to M.A.L, and National Institutes of Health K08 (K08CA124804) and Sontag Foundation Distinguished Scientist Award to S.K. This article refers to supplementary materials, which are designated by Table W1 and Figures W1 to W6 and are available online at www.neoplasia.com. Received 16 September 2008; Revised 22 October 2008; Accepted 23 October 2008 Copyright © 2009 Neoplasia Press, Inc. All rights reserved 1522-8002/09/$25.00 DOI 10.1593/neo.81180 www.neoplasia.com Volume 11 Number 1 January 2009 pp. 77–86 77