Expression of cathepsin B and cystatin C in human breast cancer

Cathepsin B, which was originally found to be a lysosomal cysteine protease , is also an important matrix protease. In this study, we investigated the expression of cathepsin B and cystatin C, the strongest inhibitor of cathep sin B, and measured the relative amounts of each in human breast cancer tis sues. Cystatin C expression relative to cathepsin B expression was found to be decreased. This finding could be associated with the looseness of cance rous interstitial tissue, which might play a role in cancer invasion and me tastasis. This report documents the first simultaneous investigation of cat hepsin B and cystatin C in breast cancer tissues.