The specific role of isoflavones on estrogen metabolism in premenopausal women

Abstract

Cancer is a genetic disease of somatic cells. Tumor karyotypes are rarely normal, and most show multiple abnormalities of both number and structure. The first direct evidence for this concept of cancer came from studies of tumor‐specific translocations in leukemias and lymphomas, revealing the importance of oncogenes and the regulation of gene transcription in cancer. A second major source of information about human cancer genes is hereditary cancer. Genetic predisposition of the autosomal dominant type imposes a high relative risk for one or more kinds of cancer. In the past decade or so, more than 30 mutant genes for such hereditary cancers have been cloned. Penetrance depends upon additional, somatic, mutations. A few of the genes are oncogenes or DNA repair genes, but most are tumor suppressor genes. Some tumor suppressors regulate transcription, while others operate in signal transduction pathways that are involved in regulating processes of cell birth, differentiation, and death. The knowledge gained is stimulating new approaches to the treatment and prevention of cancer. © 2002 Wiley‐Liss, Inc.

Soybean products and reduction of breast cancer risk: a case–control study in Japan

“…Studies examining the effect of a soy protein diet on the menstrual cycle have demonstrated a significant increase in follicular phase length and delay in menstruation, including suppression of midcycle surges of LH and FSH, which potentially may reduce the risk of breast cancer (Cassidy et al, 1994;Lu et al, 1996;Nagata et al, 1998;Kumar et al, 2002). Isoflavones have in fact received a great deal of attention due to their antiproliferative properties and these would support the protective effect against breast cancer in premenopausal women observed in the present study.…”

Does equol production determine soy endocrine effects?

“…By competing with endogenous oestrogen for ERs, thereby reducing the bioavailability of endogenous oestrogen, isoflavones may hypothetically lower the risk of breast cancer in postmenopausal women [96]. Isoflavones may also increase the serum levels of sex hormone-binding globulin (SHBG) so decreasing the levels of free estradiol [96,97]. A meta-analysis, however, did not show significant effects of isoflavone consumption on the circulating reproductive hormone concentrations (including oestrogen and SHBG) in pre-and postmenopausal women.…”

“…Higher endogenous oestrogen concentration is associated with a higher risk of breast cancer development. By competing with endogenous oestrogen for ERs, thereby reducing the bioavailability of endogenous oestrogen, isoflavones may hypothetically lower the risk of breast cancer in postmenopausal women [96]. Isoflavones may also increase the serum levels of sex hormone-binding globulin (SHBG) so decreasing the levels of free estradiol [96,97].…”

Interaction of soy and 17β-HSD1 gene polymorphisms in the risk of endometrial cancer

“…In premenopausal women, on the other hand, soy protein may reduce circulating E2 concentration by inhibiting 17β-HSD1 activity in the ovaries. A number of human intervention trials, although not all [19], have found that high intake of either isoflavones or soy foods reduce blood E2 levels among premenopausal women [20][21][22][23]. We found in a previous report that the risk of endometrial cancer was reduced only among those whose daily intake of isoflavones was equal to or greater than 43 mg/day, particularly for those who consumed over 62 mg of isoflavones per day [4].…”

“…We found in a previous report that the risk of endometrial cancer was reduced only among those whose daily intake of isoflavones was equal to or greater than 43 mg/day, particularly for those who consumed over 62 mg of isoflavones per day [4]. Interestingly, the intervention trial with a significant finding was also mainly restricted to those with a higher supplementation level of isoflavones (> 100 mg/day) or those using a more potent form of isoflavone (genistein) [20,21,23]. In this study, we also found the interaction with genotype was only significant for soy isoflavones, but not soy protein, indicating that it is the phytoestrogen isoflavones from soy that play a major role.…”