Effects of Bowman-Birk inhibitor on rat colon carcinogenesis

The present study was undertaken to determine whether the Bowman-Birk inhibitor (BBI) could prevent colon carcinogenesis in rats treated with dimethylhydrazine (DMH) and whether there were adverse side effects associated with treatment with BBI for cancer prevention. BBI was evaluated in the forms of purified BBI (PBBI) or an extract of soybeans enriched in BBI, termed BBI concentrate (BBIC). The results demonstrate that PBBI and BBIC reduced the incidence and frequency of tumors in DMH-treated rats compared with animals treated with DMH alone. Autoclaved BBIC, in which the protease inhibitor activity of BBI was destroyed, had a weak and statistically insignificant, suppressive effect on DMH-induced colon carcinogenesis in rats, suggesting that the protease inhibitor activity of BBI is likely to be responsible for the anticarcinogenic activity of BBIC. Soy molasses, which contains soy isoflavones, did not have an effect on colon cancer carcinogenesis in DMH-treated rats. Similar to results from previous studies (Nauss et al. JNCI 73, 915-924, 1984), the most aggressive, malignant colon adenocarcinomas developed within or in association with gut-associated lymphoid tissue aggregates. No adverse side effects on the pancreas or animal growth were observed in rats treated with PBBI or BBIC. These results demonstrate that PBBI and BBIC may be used to prevent colon cancer without significant adverse side effects.