We found that i) cathepsin B, but not cathepsins L and D, was highly expressed at the surface of metastatic but not of primary melanoma cell lines and that ii) CA-074, or specific antibodies to cathepsin B, hindered metastatic cell spreading and dissemination, whereas neither chemical nor biological inhibitors of cathepsins D and L had significant effects.Accordingly, in vivo studies, i.e. in murine xenografts, demonstrated that CA-074 significantly reduced human melanoma growth and the number of artificial lung metastases.
In the present study, we investigated the expression and localization of the lysosomal cysteine proteinase cathepsin B and its natural inhibitors cystatin A, B and C in high- (MV3), intermediate- (SKmel28) and low-invasive (SKmel23, WM164) human melanoma cell lines grown on plastic or in contact with monomeric or fibrillar collagen type I.
Neither the transcript levels of cathepsin B nor those of the natural inhibitors, cystatin B and C, were altered by the interaction of melanoma cells with collagen type I.
Stable antisense cathepsin B-expressing clones of the highly metastatic human melanoma A375M and prostate carcinoma PC3M cell lines produced 40-50% less cathepsin B than control cells and were proportionately less invasive.