Expression of integrin alpha(nu)beta(3) correlates with activation of membrane-type matrix metalloproteinase-1 (MTI-MMP) and matrix metalloproteinase-2 (MMP-2) in human melanoma cells in vitro and in vivo

Activation of matrix metalloproteinase-2 (MMP-2) is mediated by binding to the complex of membrane-type matrix metalloproteinase-1 (MTI-MMP) with tiss ue inhibitor of MMP-2. (TIMP-2) on the cell surface. Binding of MMP-2 to in tegrin alpha(v)beta(3) has been implicated in presenting activated MMP-2 on the cell surface of invasive cells, but interactions with the MTI-MMP-TIMF -2 system have not been considered. Therefore, we studied the expression an d interaction of MTI-MMP, MMP-2 and TIMP-2 in the alpha(v)beta(3)-negative melanoma cell line BLM and in its beta(3)-transfected, alpha(v)beta(3)-expr essing counterpart BLM-beta(3), both on cell lines and in xenografts. Total expression levels of MMP-2, MTI-MMP and T1MP-2 did not differ markedly bet ween the alpha(v)beta(3)-negative and alpha(v)beta(3)-positive cells. Remar kable differences, however, exist in the presence of active MMP-2 and MTI-M MP. Zymography on cell lysates revealed that active MMP-2, was restricted t o alpha(v)beta(3)-positive cell line and clearly accumulated in xenografts derived from the BLM-beta(3) cells, confirming the relevance of this integr in for MMP-2 function. Western blotting of cell lysates showed that process ing of proMTI-MMP to the activated form was enhanced in BLM-beta(3). The ra tio of active and inactive MTI-MMP was 3-fold higher in the beta(3)-transfe ctants. Immunofluorescence double-labeling followed by confocal laser micro scopy showed co-localization of MTI-MMP and alpha(v)beta(3) on BLM-beta(3) cells. In xenografts from BLM-beta(3) cells, active MTI-MMP was markedly in creased. Our results demonstrate that expression of alpha(v)beta(3) in cell lines and xenografts was accompanied by an accumulation of active MTI-MMP and MMP-2. Furthermore, MTI-MMP and alpha(v)beta(3) are co-localized on the cell membrane of tumor cells, These findings suggest that activated MTI-MM P co-localized with alpha(v)beta(3) may be involved in activation of alpha( v)beta(3)-bound MMP-2. Int. J. Cancer 87: 12-19, 2000, (C) 2000 Wiley-Liss, Inc.