Regulatory role of tetraspanin CD9 in tumor–endothelial cell interaction during transendothelial invasion of melanoma cells

Abstract

Heterotypic interaction among tumor cells (TCs) and endothelial cells (ECs) may play a critical role during the vascular dissemination of neoplastic cells and during pathologic angiogenesis in tumors.To identify molecules involved in these processes, the distribution of vascular junctional proteins was first studied by immunofluorescence at sites of heterologous intercellular contact using TC-EC mosaic monolayers grown on 2-dimensional collagen. Several members of the tetraspanin superfamily, including CD9, CD81, and CD151, were found to localize at the TC-EC contact area. The localization of tetraspanins to the TC-EC heterologous contact area was also observed during the active transmigration of TCs across EC monolayers grown onto 3-dimensional collagen matrices. Dynamic studies by time-lapse immunofluorescence confocal microscopy showed an active redistribution of endothelial CD9 to points of melanoma insertion. Anti-CD9 monoclonal antibodies were found to specifically inhibit the transendothelial migration of melanoma cells; the inhibitory effect was likely caused by a strengthening of CD9-mediated heterotypic interactions of TCs to the EC monolayer. These data support a novel mechanism of tetraspanin-mediated regulation of TC transcellular migration independent of TC motility and growth during metastasis and a role for these molecules in the formation of TC-EC mosaic monolayers during tumor angiogenesis. IntroductionThe dissemination of cells from a primary tumor by invasion and metastasis represents the hallmark of malignance. 1 Invasion is the local dissemination of neoplastic tissue, whereas metastasis is the distant dissemination to secondary places of growth involving the transport of neoplastic cells through the fluid spaces of the body (blood, lymph, cerebrospinal, or peritoneal fluid). 2 Although tumor cell (TC) migration through the extracellular matrix (ECM) is required for invasion, success in metastasis requires migration through the ECM and across host cell layers (transcellular migration). 3 Because most cancer cells reach distant sites by dissemination through blood or lymphatic circulation, transendothelial migration of TCs is a crucial event in vascular metastasis formation. In addition, 2 recent works in human melanoma 4 and colon carcinoma 5 suggesting that tumor vessels are "mosaic" lined by endothelial cells (ECs) and malignant TCs extend the role of TC-EC interactions to the process of tumor angiogenesis. Thus, TC transendothelial invasion and molecules involved in TC-EC interactions could contribute to the formation of new blood vessels in tumors.Tetraspanins comprise a numerous group of proteins that have 4 putative transmembrane domains and that have been implicated in the regulation of cell development, proliferation, activation, and motility. 6,7 It has been suggested that tetraspanins may provide a bridge between ␤1 integrins and other proteins to generate functional complexes that regulate cell-cell and cell-ECM interactions. 8 The expression of many members of the tetraspanin s...

Tetraspanin CD9 induces MMP-2 expression by activating p38 MAPK, JNK and c-Jun pathways in human melanoma cells

“…These observations suggest that constant high or even elevated expression of CD9 at contact sites between invasive tumor cells and vascular endothelial cells may contribute to the transmigration of tumor cells into blood or lymphatic vessels through the basement membrane. The role of CD9 in heterotypic interactions between tumor and endothelial cells during transendothelial invasion was also demonstrated by an in vitro study of transendothelial migration of A375 melanoma cells, in which CD9 provided by endothelial rather than cancer cells was suggested to play a crucial role in the transendothelial migration (Longo et al, 2001). In addition to the CD9-mediated interactions between tumor and endothelial cells, MMP-2 induced by CD9 may contribute to transendothelial invasion of cancer cells by degrading ECM around endothelial cells.…”

Aberrant expression of tetraspanin molecules in B-cell chronic lymphoproliferative disorders and its correlation with normal B-cell maturation

“…Tetraspanin proteins are a group of structurally related membrane proteins involved in cell adhesion 1-7 motility [8][9][10][11][12][13][14][15][16] and apoptosis; 17 the exact mechanisms through which they modulate these processes remains unknown. They have four common transmembrane domains with four, six or eight cysteine residues and a CCG motif in the largest extracellular loop.…”

The tetraspanin CD9 inhibits the proliferation and tumorigenicity of human colon carcinoma cells

“…5,7,9,10 mAbs directed to the CD9 molecule have also been shown to inhibit the migration of different types of carcinoma tumor cells and the transendothelial migration of melanoma cells. [11][12][13] Therefore, the inverse correlation observed between CD9 expression and the metastatic potential could be explained, at least in part, by the effects mediated by CD9 on cell adhesion and migration through the interactions among this tetraspanin and different integrins. 2,3 We have recently described a functional conformation of CD9, detected by the anti-CD9 mAb PAINS-13, that is imposed upon association of this tetraspanin with members of the beta-1 subfamily of integrins and particularly with a6b1, a cellular adhesion receptor for laminin.…”