Antitumorigenic Effect of a Mammalian Lignan Precursor from Flaxseed.
Antitumorigenic Effect of a Mammalian Lignan Precursor from Flaxseed.
Year: 1996
Authors: L U Thompson, M M Seidl, S E Rickard, L J Orcheson, H H S Fong.
Publication Name: Nutr. Cancer.
Publication Details: Volume 26; 159.
Abstract:
Earlier work by these investigators found that flaxseed reduces the risk for mammary cancer possibly through the production of mammalian lignans. They have shown a significant reduction in tumor size when flaxseed is fed at the promotional stage of tumorigenesis and a tendency for lower tumor incidence when flaxseed is fed at the initiation stage. The authors speculated that flaxseed lignans may act as anti-estrogens and inhibit the proliferative effects of estradiol on the mammary tissue. However, because flaxseed contains other nutritional components such as fiber, ALA, phytic acid and phenolic compounds, it has not been possible to conclude that mammalian lignans and their precursors are responsible for the anti-carcinogenic effects of flaxseed. The objective of this study was to determine the effect of a primary precursor of mammalian lignans, secoisolariciresinol diglycoside (SDG), on the tumor promotion stage of cancer. The potential toxicity of SDG was also assessed through the examination of major organs for enlargement and gross abnormalities. SDG was isolated from flaxseed and tested for effects on mammary tumorigenesis in sixty rats fed a high-fat (20%) diet and treated with the carcinogen, DMBA. One week following DMBA administration, thirty rats were given a daily gavage of purified SDG at 1.5 mg/day for 20 weeks. The remaining 30 rats served as the control group. SDG treatment resulted in a significant 37% reduction in the number of tumors per tumor-bearing rat and a significant 46% reduction in the number of tumors per number of rats in each group. Urinary mammalian lignan excretion significantly increased with SDG treatment, indicating the conversion of SDG to mammalian lignans. No enlargement or gross abnormalities of the major organs were observed in the SDG treated rats. This study indicates that SDG has an anti-tumor effect when provided at the early promotion stage of tumorigenesis and may contribute to the anti-carcinogenic properties of flaxseed lignans. The authors speculated that SDG may act by inhibiting the binding of estrogen to its receptors and block estrogen-induced hypertrophy. Mammalian lignans inhibit aromatase, an enzyme involved in the production of estrone from androgens, thus reducing the tumor’s source of endogenous estrogens. Mammalian lignans have also been found to reduce tumor cell proliferation. Lignans appear to decrease the transformation of initiated cells to neoplastic cells, but their exact mechanisms remain to be determined.
