Bowman-Birk protease inhibitor and its palmitic acid conjugate prevent 7,12-dimethylbenz[a]anthracene-induced transformation in cultured mouse mammary glands

The chemopreventive effects of Bowman-Birk protease inhibitor (BBI), a soybean polypeptide, and its palmitic acid conjugate, Pal-BBI, on 7,12-dimethylbenz[a]anthracene (DMBA)-induced transformation were investigated by using an in vitro whole organ culture system of mouse mammary glands. The transformation incidence was measured as the number of glands containing nodule-like alveolar lesions (NLAL). Both BBI and Pal-BBI were effective in preventing DMBA-induced transformation, especially when added to the medium during the developing period after the exposure of mammary glands to DMBA, i.e. 35.9 and 53.4% prevention, respectively. However, when only present in the medium before the promotion period, Pal-BBI was effective in decreasing the transformation incidence (32.2%) while BBI was not (10.3%). This difference could possibly be due to the high lipophilicity and tissue retention of Pal-BBI in mammary gland cultures.