Wakame seaweed suppresses the proliferation of 7,12-dimethylbenz(a)anthracene-induced mammary tumors in rats

We examined the anti-tumor proliferation effects of wakame seaweed on 7,12- dimethylbenz(a)-anthracene (DMBA)-induced rat mammary tumor. DMBA was admin istered to 8-week-old female Sprague-Dawley rats, and rats which developed mammary tumors were assigned randomly to three groups. Commercial rat feed was used in a control group (group I-A), and two feed mixtures were prepare d, which contained commercial rat feed blended with wakame at 1.0% (group I -B) and 5.0% (group I-C) by weight. The respective feeds were given to each group for 8 weeks, and changes in mammary tumor size were compared. At the end of the experiment, mammary tumors and thyroid glands were resected to compare their weights. Serum total iodine and thyroxin (T4) levels mere mea sured, Immunohistochemical studies for bromodeoxyuridine (BrdU) labeling, t ransforming growth factor (TGF)-beta, and apoptosis were carried out in the resected tumor. Significant suppression of tumor growth was observed in gr oups I-B and I-C compared with I-A. In groups I-B and I-C, the weights of r esected mammary tumors were significantly lower and serum total iodine conc entration was significantly higher than in I-A. BrdU indices were significa ntly lower in groups I-B and I-C, compared with I-A. TGF-beta and apoptotic index were inversely related to BrdU. These results suggest that iodine is transported from the serum into mammary tissues and induces apoptosis thro ugh the expression of TGF-beta. In conclusion, wakame suppressed the prolif eration of DMBA-induced mammary tumors.