Comparative analysis of matrix metalloproteinases by immunocytochemistry, immunohistochemistry and zymography in human primary brain tumours

Matrix metalloproteinases (MMPs) are a growing family of zinc-dependent end opeptidases which are characterised by their ability to degrade various ext racellular matrix (ECM) components. The family includes collagenases, gelat inases, stromelysins, metalloelastase and membrane type metalloproteinases. Consistent with their proteolytic activities, MMPs have been implicated in a variety of physiological and pathological conditions, such as normal emb ryogenesis, tissue morphogenesis and are thought to play a role in facilita ting tumour cell invasion of the normal brain. In this comparative study, w e have used zymography, immunohistochemical and immunocytochemical techniqu es to demonstrate the expression of gelatinase-A and B (MMP-2 and 9, respec tively) and membrane type metalloproteinase (MMP-14) in 8 intrinsic human p rimary brain tumours of various histological type and grade. Zymography res ults showed that MMP-2 was the most prominent proteolytic enzyme in all the cell lines :studied (with one exception), while MMP-9 was only faintly exp ressed. However, the corresponding paraffin sections showed no expression o f either MMP-2, 9 or 14 within the tumour cells, positivity being confined to haematogenous cells and the vascular endothelium. Fluorescence immunocyt ochemical studies, using monoclonal antibodies to MMP-2, 9 and 14, showed g ranular cytoplasmic reactivity in vitro. In addition, there was strong foca l positivity at the cell membrane with MMP-14 in some high grade tumours su ggesting that MMPs are produced at the leading edge of the cell by individu al subpopulations of invading glia, in small quantities and on demand in vi vo. It can be concluded that local microenvironmental conditions in vitro a ppear to stimulate such MMP activity.