Growth inhibition and cytotoxicity induced by Bowman‐Birk inhibitor concentrate in cisplatin‐resistant human ovarian cancer cells

Bowman-Birk inhibitor (BBI) is a soybean-derived anticarcinogenic protease inhibitor that was shown to potentiate the cytotoxicity of cisplatin in our previous studies. To assess the potential of BBI as a sensitizing agent for the chemotherapy of cisplatin-resistant cancers, we evaluated the effects of a soybean concentrate enriched in BBI (known as BBI concentrate or BBIC) on cell growth and clonogenic survival of a human ovarian cancer cell line, A2780, and its cisplatin-resistant sublines, C30, and C200. The presence of BBI and BBIC in the cell culture, medium reduced the clonogenic survival of the A2780, C30, and C200 cells in a dose-dependent manner and enhanced cisplatin-induced growth inhibition and/or cytotoxicity. BBIC alone showed greater inhibitory effects on growth in the cisplatin-resistant cell lines. These results suggest that BBI and BBIC could be useful agents for the treatment of cancers, especially with cisplatin, in tumors resistant to this important anticancer agent.