A proteolytic activity in a human breast cancer cell line which is inhibited by the anticarcinogenic Bowman-Birk protease inhibitor.

Epidemiological studies suggest that human populations consuming diets rich in protease inhibitors have a reduced incidence of cancer at several sites including the breast. Protease inhibitors, such as the Bowman-Birk inhibitor (BBI) have been shown to be highly effective at suppressing carcinogenesis in a variety of experimental model systems. In this study, we have identified a protease activity in human breast epithelial cells which is inhibited by BBI. This enzyme has a molecular mass of 43 kDa, cleaves gelatin and is primarily localized in the cytosol. Protease activity is maximal at pH 8 and is inhibited by DFP, but unaffected by EDTA, indicating that this enzyme is a serine protease. The protease identified in MCF7 cells has characteristics which are similar to a protease present in human fibroblasts. Hence, our results suggest that BBI targets a common enzyme in human epithelial cells and fibroblasts.