Chemoprevention of 7,12-dimethylbenz-(α)anthracene (DMBA) induced rat mammary tumors by 2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone (ABPP)

We have studied the chemopreventive effectiveness of 2-amino-5-bromo-6-phenyl-4(3H)-pyrimidinone (ABPP) in 7,12-dimethylbenz(α)anthracene (DMBA) induced rat mammary tumors. ABPP is a biological response modifier and has various biological activities, including interferon induction, immuno-modulation, and antiviral and antineoplastic properties, both in vitro and in vivo. Fifty-day-old female Sprague-Dawley rats were randomized into two groups and all received 20 mg DMBA by gastric gavage. ABPP at 200 mg/kg weight was given to one group of rats three times a week for 4 weeks, beginning 6 h before DMBA. The other group of rats received the vehicle as controls. The rats were observed for 26 weeks, with weekly measurements of tumor development, size, and weight. Interferon titers were determined on all rats 6 h after the first dose of ABPP. After tumor induction, rats treated with ABPP persistently developed a fewer number of tumors on average than those in the control group. It was found that the mean sizes of total tumor mass per rat were consistently lower in the ABPP group starting 12 weeks after the tumor induction. This reduction of tumor size in ABPP-treated rats correlates significantly with the titers of interferon. Thus, our initial study demonstrates that ABPP seems to have chemopreventive potential, even with a brief duration of treatment, in DMBA-induced rat mammary cancers.