Inhibition of tumour cell invasion by protease inhibitors: correlation with the protease profile

The invasive potential of eight established human tumour cell lines of different origin has been studied in the Matrigel assay. Between 25% and 70% of the cells migrated through the Matrigel layer within 24 h, indicating that invasiveness varies with the cell type. Semiquantitative measurements of the proteases MMP-2 and MMP-9, and cathepsins B and L were performed in these cell lines and the cell culture media. High invasive potential was found in those cell lines expressing high levels of cathepsins B and L or matrix metal proteases (MMP), either alone or in combination. Overexpression of one of these enzymes is enough to explain a high invasive potential of a cell line. Selective protease inhibitors at 10 nM concentration in the culture medium were used to inhibit the migration of tumour cells in the Matrigel assay. The MMP inhibitor Batimastat reduced the invasive potential of all cell lines studied independently of the MMP expression. The effect of cysteine protease inhibitors was strongly correlated with the protease profile of the tumour cell line. Our findings support the hypothesis of a very complex activation cascade of matrix-degrading proteolytic enzymes and they underline the need to analyse the protease profile of any tumour before beginning an antiproteolytic tumour treatment.