Isoflavones in breast cancer chemoprevention: where do we go from here?

Abstract

Based on the evidence from epidemiological, animal, in vitro data and human clinical trials, it is evident that isoflavones are promising agents for breast cancer chemoprevention. It is also evident that the form of isoflavone used (purified vs soy products), dose of isoflavone used (low vs high), timing and duration of exposure of isoflavones appears to play a major role in determining agonistic or antagonistic effects. Collectively, these isoflavones have enough evidence to warrant use in a number of clinical trials to examine its efficacy as a potential chemopreventive agent for breast cancer. In this comprehensive review, we attempt to summarize the evidence demonstrating the potential use of isoflavones in breast cancer chemoprevention and the rationale to examine a combination of biochemical, morphological and molecular intermediate endpoint biomarkers of breast cancer risk to examine the efficacy of this promising agent.

Yarrow (Achillea millefolium L.): A Neglected Panacea? A Review of Ethnobotany, Bioactivity, and Biomedical Research1

“…Genistein was an order of magnitude more estrogenic, in terms of causing proliferation of breast cancer cells, than apigenin in van Meeuwen et al's (2007) study, and the quantity of genistein and other phytoestrogenic isoflavones in soy is substantial. Nevertheless, though concern has been raised that soy could stimulate growth of estrogen-sensitive tumors (e.g., Messina et al 2006), in the overall human population soy seems to have either no effect or a protective effect on breast cancer risk (e.g., Kumar et al 2004;Qin et al 2006). Unless some animal study using yarrow extract finds a cancer-promoting effect or significant estrogenic activity, there is no rationale for consumer concern.…”

Soy Isoflavones and Osteoporotic Bone Loss: A Review with an Emphasis on Modulation of Bone Remodeling

“…23 Its property of antidiabetic, hypolipidemic, and antiinflammatory effects may reduce risk of cardiovascular disease, while its antioxidant properties make it work as a chemopreventive agent in preventing the development of breast cancer. 24 These effects may lead to a modestly beneficial effect on maintaining or preventing bone loss. 25 To date, the ability of SI on reducing bone turnover has been demonstrated through inhibiting bone resorption and stimulating bone formation in several studies.…”

The Soy Isoflavone Equol May Increase Cancer Malignancy via Up-regulation of Eukaryotic Protein Synthesis Initiation Factor eIF4G

“…These compounds have received increasing attention for their potential estrogenic or antiestrogenic effects, leading to concerns surrounding the use of phytoestrogen supplements in breast cancer patients who may overexpress estrogen receptors in the tumor tissue (2). Because soy foods have anticancer effects at early stages of carcinogenesis, most studies have focused on breast cancer prevention by soy isoflavones (3). However, the benefits of soy foods as chemopreventives for established breast cancer or as substitutes for hormone replacement therapies remain controversial (3)(4)(5).…”

“…Because soy foods have anticancer effects at early stages of carcinogenesis, most studies have focused on breast cancer prevention by soy isoflavones (3). However, the benefits of soy foods as chemopreventives for established breast cancer or as substitutes for hormone replacement therapies remain controversial (3)(4)(5).…”