Wakame Seaweed Suppresses the Proliferation of 7,12‐Dimethylbenz(a)‐anthracene‐induced Mammary Tumors in Rats

Abstract

We examined the anti-tumor proliferation effects of wakame seaweed on 7,12-dimethylbenz(a)-anthracene (DMBA)-induced rat mammary tumor. DMBA was administered 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 prepared, 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 were measured. Immunohistochemical studies for bromodeoxyuridine (BrdU) labeling, transforming growth factor (TGF)-β β β β, and apoptosis were carried out in the resected tumor. Significant suppression of tumor growth was observed in groups I-B and I-C compared with I-A. In groups I-B and I-C, the weights of resected mammary tumors were significantly lower and serum total iodine concentration was significantly higher than in I-A. BrdU indices were significantly lower in groups I-B and I-C, compared with I-A. TGF-β β β β and apoptotic index were inversely related to BrdU. These results suggest that iodine is transported from the serum into mammary tissues and induces apoptosis through the expression of TGF-β β β β. In conclusion, wakame suppressed the proliferation of DMBA-induced mammary tumors.

A case–control study on seaweed consumption and the risk of breast cancer

“…Miyeok intake did not show any significant associations with the risk of breast cancer in the present study, a finding which may be due to the low consumption frequency and low variation in miyeok intake among the subjects. However, U. pinnatifida (miyeok) has been reported to suppress mammary tumour growth in rats (25) , while fucoidan and fucoxanthin from U. pinnatifida has antitumour (39,40) and antioxidant activities (41) . Therefore, further studies are needed to investigate the relationship between miyeok intake and breast cancer risk in other research settings including areas with a large variation of miyeok intake.…”

“…Iodine acts as an antioxidant and antiproliferative agent, which contributes to the integrity of the normal mammary gland (44) . The addition of seaweeds (Laminaria, Porphyra tenera and wakame: miyeok) to the diet and iodine supplement showed a suppressive effect on the development and size of both benign and cancer neoplasias in animal studies (10,25,45,46) . Taken together, these results indicate that the protective effect of gim on the risk of breast cancer may be attributed to the antioxidant and antitumour activities of gim components such as polysaccharides, protein, polyphenol, carotenoids (16) , chlorophyll (16) and iodine, etc.…”

Seaweed Prevents Breast Cancer?

“…We have been studying the relationship between iodine and breast cancer for 10 years, trying to determine whether iodine is useful for chemoprevention of breast cancer. [6][7][8] There have been several reports on the relationship of iodine and breast cancer, [9][10][11] but the present paper is the first concerning breast cancer chemoprevention by seaweed.…”

“…However, this dose, if scaled up to the human body weight, is too large to be practicable. 8) In the present experiments, mekabu was used instead of wakame. It contained almost the same amount of iodine as the wakame used in our former experiments (5.9 vs. 5.7 mg/100 g), but is cheaper and easier to process than wakame.…”

Variability of Iodine Content in Common Commercially Available Edible Seaweeds

“…In an earlier study, we and others reported that dietary seaweed delayed the time to tumor onset in a rat dimethylbenzanthracene mammary-induced cancer model (3)(4)(5)(6)(7). In preparation for a clinical study in humans, it was necessary to evaluate common edible seaweeds for iodine content since excess iodine intake might adversely affect thyroid function.…”