Rice Suman, Whitehead Saffron A
Division of Basic Medical Sciences, St George's University of London, Cranmer Terrace, London SW17 0RE, UK.
Endocr Relat Cancer. 2006 Dec;13(4):995-1015. doi: 10.1677/erc.1.01159.
The majority of breast cancers are oestrogen dependent and in postmenopausal women the supply of oestrogens in breast tissue is derived from the peripheral conversion of circulating androgens. There is, however, a paradox concerning the epidemiology of breast cancer and the dietary intake of phytoestrogens that bind weakly to oestrogen receptors and initiate oestrogen-dependent transcription. In Eastern countries, such as Japan, the incidence of breast cancer is approximately one-third that of Western countries whilst their high dietary intake of phytoestrogens, mainly in the form of soy products, can produce circulating levels of phytoestrogens that are known experimentally to have oestrogenic effects. Indeed, their weak oestrogenicity has been used to advantage by herbalist medicine to promote soy products as a natural alternative to conventional hormone replacement therapy (HRT). Such usage could increase in light of recent evidence that long-term HRT usage may be associated with an increased risk of breast cancer with a consequent reduction in prescription rates. So, are phytoestrogens safe as a natural alternative to HRT and could they be promoters or protectors of breast cancer? If they are promoters, then we must assume that it is due to their oestrogenic effect. If they are protectors, then other actions of phytoestrogens, including their ability to inhibit enzymes that are responsible for converting androgens and weak oestrogens into oestradiol, must be considered. This paper addresses these questions by reviewing the actions of phytoestrogens on oestrogen receptors and key enzymes that convert androgens to oestrogens in relation to the growth of breast cancer cells. In addition, it compares the experimental and epidemiological evidence pertinent to the potential beneficial or harmful effects of phytoestrogens in relation to the incidence/progression of breast cancer and their efficacy as natural alternatives to conventional HRT.
大多数乳腺癌依赖雌激素，在绝经后女性中，乳腺组织中的雌激素供应来自循环雄激素的外周转化。然而，关于乳腺癌的流行病学与植物雌激素的饮食摄入存在一个矛盾之处，植物雌激素与雌激素受体的结合较弱，并启动雌激素依赖性转录。在日本等东方国家，乳腺癌的发病率约为西方国家的三分之一，而他们从饮食中大量摄入植物雌激素，主要是以豆制品的形式，这会使植物雌激素的循环水平升高，实验表明这些植物雌激素具有雌激素效应。事实上，草药医学利用它们较弱的雌激素性，将豆制品作为传统激素替代疗法（HRT）的天然替代品来推广。鉴于最近的证据表明长期使用HRT可能与乳腺癌风险增加相关，从而导致处方率下降，这种用法可能会增加。那么，植物雌激素作为HRT的天然替代品是否安全？它们会是乳腺癌的促进剂还是保护剂呢？如果它们是促进剂，那么我们必须假定这是由于它们的雌激素效应。如果它们是保护剂，那么就必须考虑植物雌激素的其他作用，包括它们抑制负责将雄激素和弱雌激素转化为雌二醇的酶的能力。本文通过回顾植物雌激素对雌激素受体以及与乳腺癌细胞生长相关的将雄激素转化为雌激素的关键酶的作用来探讨这些问题。此外，本文还比较了与植物雌激素对乳腺癌发病率/进展的潜在有益或有害影响以及它们作为传统HRT天然替代品的功效相关的实验和流行病学证据。
