To determine the biological effect of biochanin A, miso or NaCl and sexual influence of testosterone on liver tumor induction, male and female BCF1 mice were i.p. injected once with DEN at a dose of 5 mug/g body weight at 15 days of age. In order to shorten the latency of liver tumor occurrence, the whole body of mice were exposed to 2 Gy of Cf-252 fission neutrons at four weeks of age. Three days later, female mice were surgically ovariectomized and given the various doses of testosterone melted into a cholesterol pellet. Male mice were fed on 10 ppm, 20 ppm biochanin A, 10% miso or 2% NaCl supplemented diet for 8 weeks (from 21 to 28 weeks of age) and 4 weeks (from 32 to 36 weeks of age). All mice were sacrificed at 40 weeks of age. Multiplicity of liver tumors was expressed in four different size ranges by <2, 3-5, 6-10 and >10 mm2. Incidence of liver tumors in all experimental groups except in group 1 at 20 weeks were observed at 100%. Average tumor size and multiplicity were smaller at 20 weeks compared to those of 40-week groups. Male groups fed 20 ppm biochanin A and 2% NaCl had an increase in body weight with significant difference from control by p<0.01. Liver weights were more-or-less the same in all groups except an increase was seen in the group of 20 ppm biochanin A (p<0.01). In female groups, both 0.2 mg and 1 mg of testosterone administration resulted in an increase of tumor multiplicities and a decrease of liver weight compared to that of control group with significant differences. In both male and female groups, majority of liver tumor sizes were in the range of 3-5 mm2. Tumor multiplicities and size in less than 2 mm2 in biochanin A groups, 10% miso and 2% NaCl decreased significantly from control group. These findings suggest that 15-20 weeks is the time in which 1-2 mm2 size of liver tumors start to appear. Among others, biochanin A is a component of miso. The potent anti-tumorigenic effect of dietary miso for mouse liver tumorigenesis may be strenghtened by a combination of factors such as the presence of Biochanin A, protease inhibitors and various fermented enzymes.

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