Association between selenium intake and breast cancer risk: results from the Women's Health Initiative.

PURPOSE: It has been hypothesized that selenium (Se) can prevent cancer, and that Se deficiency may be associated with an increased risk of breast cancer. However, findings from epidemiological studies have been inconsistent. The objective of this study was to assess the association between Se intake and risk of breast cancer in the Women's Health Initiative (WHI). METHODS: This study included 145,033 postmenopausal women 50-79 years who completed baseline questionnaires between October 1993 and December 1998, which addressed dietary and supplemental Se intake and breast cancer risk factors. The association between baseline Se intake and incident breast cancer was examined in Cox proportional hazards analysis. RESULTS: During a mean follow-up of 15.5 years, 9487 cases of invasive breast cancer were identified. Total Se (highest versus lowest quartile: HR 1.00, 95% CI 0.92-1.09, Ptrend = 0.66), dietary Se (highest versus lowest quartile: HR 0.99, 95% CI 0.89-1.08, Ptrend = 0.61), and supplemental Se (yes versus no: HR 0.99, 95% CI 0.95-1.03) were not associated with breast cancer incidence. CONCLUSIONS: This study indicates that Se intake is not associated with incident breast cancer among postmenopausal women in the United States. Further studies are needed to confirm our findings by using biomarkers such as toenail Se to reduce the potential for misclassification of Se status.

Effect of Epilobium angustifolium and Serenoa repens extracts on regulation of non-genomic signaling pathway of kinases.

OBJECTIVES: Changes of kinase activity of non-genomic cellular signaling pathway may influence the effectiveness of pharmacotherapy in case of hormone-dependent tumors. Our study investigated a possible interaction at the molecular level between an aqueous herbal extract of Epilobium angustifolium as well as a lipid-sterolic fruit extract of Serenoa repens and synthetic drugs used in the treatment of hormone-dependent cancers. MATERIAL AND METHODS: E. angustifolium and Serenoa repens extracts were orally administered to testosterone-induced rats for 21 days. Changes of RafA/Mapk3/Mapk1 mRNA levels were analyzed by real-time quantitative PCR using target specific primers. RESULTS: The level of RafA mRNA slightly increased in rats receiving Epilobium angustifolium (p = 0.076) and Serenoa repens (p = 0.016) extracts. Administration of these extracts resulted in significantly elevated Mapk1 and Mapk3 transcripts in the investigated animals (p < 0.05 for each extract). The levels of Mapk1 and Mapk3 mRNA strongly increased (p < 0.05 for each extract) in animals receiving concomitantly testosterone and the extracts, while RafA transcription slightly decreased (p < 0.05), as compared to controls. CONCLUSIONS: The results of our study may indicate a potential effect of S. repens and E. angustifolium extracts on the functioning of non-genomic cellular signaling kinases pathway. We investigated safety of these extracts to detect possible drug interactions between synthetic drugs used in the treatment of proliferative changes in hormone-dependent reproductive organs and herbal preparations.

Soy and its isoflavones: the truth behind the science in breast cancer.

Epidemiological and migratory evidence suggests that dietary soy consumption can lower the risk for breast cancer. The role of soy isoflavones in cancer prevention and promotion is somewhat unclear. There are two views in terms of soy isoflavones and breast cancer. One line of evidence suggests that soy and its isoflavones have exhibited cancer-preventive properties including lengthening the menstrual cycle, altering estrogen metabolism away from cancerous compounds, and demonstrating anti-proliferative properties in vivo. On the contrary, isoflavones found in soy products are suggested to behave as weak estrogens and as such, much speculation surrounds the influence of soy and/or its isoflavones on hormone-receptor-positive cancers. The objective of this review is to present the latest knowledge regarding the role of soy and its isoflavones with the development and advancement of breast cancer, the safety of soy isoflavones for breast cancer survivors, and a comparison of the carcinogenic effects in animal models following soy isoflavone and estrogen administration. This review compares and contrasts literature in terms of the anti-cancer and cancer-promoting effects of soy isoflavones and estrogen in humans and animal models. In conclusion, current human and animal data provide evidence for several anticancer properties of soy and/or its isoflavones. Although the specific quantities and constituents responsible for the observed anti-cancer effects have not been elucidated, it appears that soy isoflavones do not function as an estrogen, but rather exhibit anti-estrogenic properties. However, their metabolism differs between humans and animals and therefore the outcomes of animal studies may not be applicable to humans. The majority of breast cancer cases are hormone-receptor-positive; therefore, soy isoflavones should be considered a potential anti-cancer therapeutic agent and warrant further investigation.

The potential therapeutic benefits of vitamin D in the treatment of estrogen receptor positive breast cancer.

Calcitriol (1,25-dihydroxyvitamin D(3)), the hormonally active form of vitamin D, inhibits the growth of many malignant cells including breast cancer (BCa) cells. The mechanisms of calcitriol anticancer actions include cell cycle arrest, stimulation of apoptosis and inhibition of invasion, metastasis and angiogenesis. In addition we have discovered new pathways of calcitriol action that are especially relevant in inhibiting the growth of estrogen receptor positive (ER+) BCa cells. Calcitriol suppresses COX-2 expression and increases that of 15-PGDH thereby reducing the levels of inflammatory prostaglandins (PGs). Our in vitro and in vivo studies show that calcitriol decreases the expression of aromatase, the enzyme that catalyzes estrogen synthesis selectively in BCa cells and in the mammary adipose tissue surrounding BCa, by a direct repression of aromatase transcription via promoter II as well as an indirect effect due to the reduction in the levels of PGs, which are major stimulator of aromatase transcription through promoter II. Calcitriol down-regulates the expression of ERα and thereby attenuates estrogen signaling in BCa cells including the proliferative stimulus provided by estrogens. Thus the inhibition of estrogen synthesis and signaling by calcitriol and its anti-inflammatory actions will play an important role in inhibiting ER+BCa. We hypothesize that dietary vitamin D would exhibit similar anticancer activity due to the presence of the enzyme 25-hydroxyvitamin D-1α-hydroxylase (CYP27B1) in breast cells ensuring conversion of circulating 25-hydroxyvitamin D to calcitriol locally within the breast micro-environment where it can act in a paracrine manner to inhibit BCa growth. Cell culture and in vivo data in mice strongly suggest that calcitriol and dietary vitamin D would play a beneficial role in the prevention and/or treatment of ER+BCa in women.

Inter-related in vitro effects of androgens, fatty acids and oxidative stress in prostate cancer: a mechanistic model supporting prevention strategies.

Oxidation of mitochondrial fatty acids (FA) results in the generation of reactive oxygen species (ROS) which have been postulated to play a key role in the initiation and progression of prostate cancer (PC). We previously reported that androgens increase FA uptake into PC cells. We thus examined if androgens that are known to induce ROS generation regulate FA oxidation in PC cells. The effects of the androgen-depleted medium, R1881 (synthetic androgen) and/or androgen receptor blocker, bicalutamide were examined in the human androgen-responsive but not dependent 22rv1 cells. R1881 supplementation significantly increased mitochondrial FA oxidation ((14)C-radiolabeled FA degradation studies), resulting in increased ROS production. Androgens increased the mRNA levels of carnitine palmitoyltransferase (CPT1), the rate limiting enzyme in the process of mitochondrial FA oxidation. Treatment with R1881 and bicalutamide inhibited these androgen regulated effects. Inhibition of mitochondrial ROS generation by two different inhibitors, rotenone and thenoyltrifluoroacetone, eliminated the androgen-induced ROS generation, to the same level as in cells deprived of androgens or treated with R1881 and bicalutamide. Taken together, androgens increase the mitochondrial oxidation of FA, leading to increased production of ROS that is associated with prostate cell proliferation and mutagenesis. These results therefore support the rationale for PC prevention using 5-alpha reductase inhibitors, dietary restrictions or anti-oxidants, each of which has different inhibitory but complementary effects.

Berries and ellagic acid prevent estrogen-induced mammary tumorigenesis by modulating enzymes of estrogen metabolism.

To determine whether dietary berries and ellagic acid prevent 17beta-estradiol (E(2))-induced mammary tumors by altering estrogen metabolism, we randomized August-Copenhagen Irish rats (n = 6 per group) into five groups: sham implant + control diet, E(2) implant + control diet (E(2)-CD), E(2) + 2.5% black raspberry (E(2)-BRB), E(2) + 2.5% blueberry (E(2)-BB), and E(2) + 400 ppm ellagic acid (E(2)-EA). Animals were euthanized at early (6 wk), intermediate (18 wk), and late (24 wk) phases of E(2) carcinogenesis, and the mammary tissue was analyzed for gene expression changes using quantitative real-time PCR. At 6 weeks, E(2) treatment caused a 48-fold increase in cytochrome P450 1A1 (CYP1A1; P < 0.0001), which was attenuated by both BRB and BB diets to 12- and 21-fold, respectively (P < 0.001). E(2) did not alter CYP1B1 levels, but both berry and EA diets significantly suppressed it by 11- and 3.5-fold, respectively, from baseline (P < 0.05). There was a 5-fold increase in 17beta-hydroxysteroid dehydrogenase 7 (17betaHSD7), and this was moderately abrogated to approximately 2-fold by all supplementation (P < 0.05). At 18 weeks, CYP1A1 was elevated by 15-fold in E(2)-CD and only E(2)-BB reduced this increase to 7-fold (P < 0.05). Catechol-O-methyltransferase expression was elevated 2-fold by E(2) treatment (P < 0.05), and all supplementation reversed this. At 24 weeks, CYP1A1 expression was less pronounced but still high (8-fold) in E(2)-treated rats. This increase was reduced to 3.2- and 4.6-fold by E(2)-BRB and E(2)-EA, respectively (P < 0.05), but not by E(2)-BB. Supplementation did not alter the effect of E(2) on steroid receptors. The diets also significantly suppressed mammary tumor incidence (10-30%), volume (41-67%), and multiplicity (38-51%; P < 0.05). Berries may prevent mammary tumors by suppressing the levels of E(2)-metabolizing enzymes during the early phase of E(2) carcinogenesis.

Null activity of selenium and vitamin e as cancer chemopreventive agents in the rat prostate.

To evaluate the potential efficacy of selenium and vitamin E as inhibitors of prostate carcinogenesis, four chemoprevention studies using a common protocol were done in a rat model of androgen-dependent prostate cancer. After stimulation of prostate epithelial cell proliferation by a sequential regimen of cyproterone acetate followed by testosterone propionate, male Wistar-Unilever rats received a single i.v. injection of N-methyl-N-nitrosourea (MNU) followed by chronic androgen stimulation via subcutaneous implantation of testosterone pellets. At 1 week post-MNU, groups of carcinogen-treated rats (39-44/group) were fed either a basal diet or a basal diet supplemented with l-selenomethionine (3 or 1.5 mg/kg diet; study 1), dl-alpha-tocopherol (vitamin E, 4,000 or 2,000 mg/kg diet; study 2), l-selenomethionine + vitamin E (3 + 2,000 mg/kg diet or 3 + 500 mg/kg diet; study 3), or selenized yeast (target selenium levels of 9 or 3 mg/kg diet; study 4). Each chemoprevention study was terminated at 13 months post-MNU, and prostate cancer incidence was determined by histopathologic evaluation. No statistically significant reductions in prostate cancer incidence were identified in any group receiving dietary supplementation with selenium and/or vitamin E. These data do not support the hypotheses that selenium and vitamin E are potent cancer chemopreventive agents in the prostate, and when considered with the recent clinical data reported in the Selenium and Vitamin E Cancer Prevention Trial (SELECT), show the predictive nature of this animal model for human prostate cancer chemoprevention.

Chemopreventive actions by enterolactone and 13 VIOXX-related lactone derivatives in H295R human adrenocortical carcinoma cells.

Cytochrome P450c17 (CYP17) has been linked to various hormone-related diseases, including breast cancer, thus being a potential target for cancer chemoprevention. We studied the naturally occurring phytochemical enterolactone (ENL) and 13 VIOXX-related lactone derivatives (CRI-1 to CRI-13) for their effects on CYP17 activity and expression and on cell cycle status in the human H295R adrenocorticocarcinoma cell line. Of the tested compounds, only CRI-3, -7, -10 and -12 showed to be inhibitors of CYP17 activity in H295R cells. This inhibition was not due to decreased mRNA expression, but was apparently caused by post-translational modification of the CYP17 enzyme. The MAPK kinase (MEK) inhibitor PD98059 induced CYP17 activity by 24%, while co-incubation of the CRI-s with PD98059, reduced CYP17 activity even further than the reduction caused by the CRI-s alone. In addition, CRI-3, -7, -10 and -12 arrested the cell cycle in the G(2)/M phase. The structure-activity similarities of the CRI-s with known micro-tubule binding agents strongly suggest that cell cycle arrest is a result of interaction with tubulin. We conclude that the proposed cancer chemopreventive actions of ENL are not mediated through interaction with CYP17 or cell cycle status. Of the VIOXX-related lactone derivatives, CRI-7 could prove useful in the prevention of hormone-dependent cancers, such as breast cancer, since in vitro it shows low cytotoxicity, it is a potent inhibitor of CYP17 activity and strong inducer of cell cycle arrest.

Resveratrol and chemoprevention.

Resveratrol is a phytoalexin, highly abundant in skins of red grapes and moderately abundant in peanuts and blueberries. Originally a constituent of oriental medicines, it has lately been rediscovered for a plethora of beneficial properties such as anti-cancer, anti-aging, antiviral, cardiovascular and neuroprotective effects, thereby making it one of the most sought after phytochemicals for supplementing human diet. Studies done in various laboratories have shown its modulatory effects on multitudes of cell signaling and gene expression pathways. Although most of its effects have been observed in cultured cells, quite a few have also been validated in whole animals as well. It is thus necessary to have a comprehensive look at all those effects of resveratrol in an organismal context. The following review summarizes the effects of resveratrol in the context of chemoprevention.

Efficacy of sulforaphane is mediated by p38 MAP kinase and caspase-7 activations in ER-positive and COX-2-expressed human breast cancer cells.

Sulforaphane is an antioxidant and a potent stimulator of natural detoxifying enzyme and associated with lowered risk of cancer that is associated with the consumption of cruciferous vegetables. The chemopreventive effects of SFN was investigated using the MCF-7 human breast cancer cells and the M13SV1-immortalized human breast luminal epithelial cells. Sulforaphane reduced proliferation in MCF-7 cells and inhibited cyclooxygenase-2 expression in M13SV1 cells treated with 12-O-tetradecanoylphorbol-13-acetate (TPA). The chemopreventive effects of sulforaphane were associated with p38 mitogen-activated protein kinase suggest its important role in cell survival/apoptosis regulation and stabilization of cyclooxygenase-2. Sulforaphane upregulates p38 in MCF-7 cells and prevented TPA-reduced phosphorylation of p38 in M13SV1 cells, but activated caspase-7 associated with apoptosis in MCF-7 cells. These results suggest that sulforaphane may be an alternative candidate for targeted prevention of ER-positive and cyclooxygenase-2-induced phenotypes and breast cancer.

Preventive effects of glycyrrhizin on estrogen-related endometrial carcinogenesis in mice.

We have previously reported on the inhibitory effect of Glycyrrhizae radix (Gl radix) on mouse endometrial carcinogenesis. The present study was performed to clarify the effects of Gl radix and glycyrrhizin (GL), the main part of Gl radix, on estradiol (E2)-related endometrial carcinogenesis. Both Gl radix and GL exerted a significant decrease in the COX-2, IL-1alpha and TNF-alpha mRNA expressions. GL generated a significant decrease in the incidence of endometrial adenocarcinoma. Accordingly, the preventive effects of Gl radix may be attributable to GL, thus being related with the suppression of COX-2, IL-1alpha and TNF-alpha. Gl radix and GL could therefore be a promising formula for the chemoprevention of human endometrial cancer.

Coffee consumption and the risk of endometrial cancer: Evidence from a case-control study of female hormone-related cancers in Japan.

Coffee has become a popular beverage worldwide. Caffeine, a major ingredient of coffee, has been proposed to have a favorable affect on the modulation of circulating estrogen levels and therefore may be of importance in developments on hormone-related cancers. However, epidemiological evidence is limited and inconsistent. We examined the relationship between intake of coffee and hormone-related cancer risk among Japanese women using data from the hospital-based epidemiological research program at Aichi Cancer Center (HERPACC). In total, 2122 breast, 229 endometrial and 166 ovarian cancer cases were included, and 12 425 women, confirmed as free of cancer, were recruited as the control group. Odds ratios (OR) and 95% confidence intervals (95% CI) were determined by multiple logistic regression analysis. A statistically significant inverse association between risk of endometrial cancer and coffee consumption was noted in Japanese women, with no clear association evident for breast and ovarian cancer risk. Compared to non-drinker, the OR of daily drinking of 1-2 cups and 3 or more cups per day for endometrial cancer were 0.64 (95% CI: 0.43-0.94) and 0.41 (95% CI: 0.19-0.87), respectively, and the linear trend was also statistically significant (P < 0.01). However, there was no statistically significant association between caffeine intake and endometrial cancer. In summary, the results of the present study suggest that coffee consumption reduces the risk of endometrial cancer in Japanese subjects. Given the scarcity of studies of coffee intake and endometrial cancer and other hormone-dependent cancer risk, additional investigations are warranted.

Ethanolic extracts of black cohosh (Actaea racemosa) inhibit growth and oestradiol synthesis from oestrone sulphate in breast cancer cells.

Extracts of black cohosh (Actaea racemosa) and soy are used as 'natural' alternatives to conventional hormone replacement therapy (HRT) and there is some evidence that soy may protect against breast cancer by inhibiting the production of active oestrogens. This study compares the action of ethanolic extracts of black cohosh (BCE) and genistein on growth and enzyme activity in MCF-7 and MDA-MB-123 breast cancer cells. BCE inhibited growth at the two highest doses tested, i.e. 50 and 100 microg/ml, whilst genistein stimulated growth in the oestrogen receptor positive (ER(+)) MCF-7 cells, but at high doses it inhibited growth in both cell lines. BCE did not affect the conversion of androstenedione to oestradiol and only the highest doses (50 and 100 microg/ml) significantly inhibited the conversion of oestrone to oestradiol in MDA cells. In contrast, BCE induced a dose-dependent inhibition of the conversion of oestrone sulphate to oestradiol in both cell lines, whilst in human granulosa lutein (GL) cells enzyme activity was only inhibited at the highest dose of BCE. Genistein had no significant effect on enzyme activity in breast cancer cells and like BCE only the highest doses (10 and 50 microM) inhibited enzyme activity in human GL cells. In vivo genistein may have growth stimulatory effects on breast tissue but BCE not only inhibits growth but inhibits the conversion of oestrone sulphate to active oestradiol, considered by some, to be the preferred pathway of oestradiol synthesis in breast tissue.

Addressing the soy and breast cancer relationship: review, commentary, and workshop proceedings.

The impact of soyfood intake on breast cancer risk has been investigated extensively. Much of this focus can be attributed to the soybean being a dietary source that is uniquely rich in isoflavones. The chemical structure of isoflavones is similar to that of estrogen, and isoflavones bind to both estrogen receptors (ER alpha and ER beta) (although they preferentially bind to and activate ER beta) and exert estrogen-like effects under some experimental conditions. Isoflavones also possess nonhormonal properties that are associated with the inhibition of cancer cell growth. Thus, there are several possible mechanisms by which soy may reduce the risk of breast cancer. However, the role of isoflavones in breast cancer has become controversial because, in contrast to the possible beneficial effects, some data from in vitro and animal studies suggest that isoflavones, especially genistein, the aglycone of the main soybean isoflavone genistin, may stimulate the growth of estrogen-sensitive tumors. Limited human data directly address the tumor-promoting effects of isoflavones and soy. Because the use of soyfoods and isoflavone supplements is increasing, it is important from a public health perspective to understand the impact of these products on breast cancer risk in women at high risk of the disease and on the survival of breast cancer patients. To this end, a workshop was held in November 2005 to review the existing literature and to make research recommendations. This paper summarizes the workshop findings and recommendations. The primary research recommendation is that the impact of isoflavones on breast tissue needs to be evaluated at the cellular level in women at high risk for breast cancer.

[Prevention of prostate cancer]. / Prävention des Prostatakarzinoms.

Prostate cancer has become the most frequently diagnosed male cancer next to non-melanotic skin cancer in the Western world. Preventive measures would therefore have important potential effects on the incidence and prevalence of this disease. A potential for effective prevention of prostate cancer is currently seen in dietary changes and perhaps in dietary supplementation with vitamins D and E or selenium. Pharmacological prevention seems a possibility with drugs acting on intraprostatic testosterone metabolism. Several large randomised trials are ongoing to clarify the potential for successful prostate cancer prevention.

Inhibition of cyclooxygenase (COX)-2 expression by Tet-inducible COX-2 antisense cDNA in hormone-refractory prostate cancer significantly slows tumor growth and improves efficacy of chemotherapeutic drugs.

PURPOSE: Overexpression of the proinflammatory enzyme cyclooxygenase (COX)-2 is associated with the progression of various malignancies; the role of COX-2 in prostate cancer is less clear. The significance of COX-2 in prostate cancer growth and response to chemotherapy was investigated in an androgen-refractory prostate cancer cell line using a Tet-inducible antisense COX-2 expression system. EXPERIMENTAL DESIGN: An antisense COX-2 cDNA construct under the control of a doxycycline-inducible promoter was transfected into a prostate cancer cell line, PC-3ML. Modulations of cell growth, apoptosis, and chemosensitivity in the presence or absence of doxycycline were analyzed. Tumor incidence, growth rate, and response to two cytotoxic drugs, COL-3 [chemically modified tetracycline-3-(6-demethyl-6-deoxy-4-dedimethylamino-tetracycline)] and Taxotere (docetaxel), were investigated in tumor xenografts. Apoptotic incidences and tumor microvessel density in tumors were determined by immunohistochemistry. RESULTS: Conditional suppression of COX-2 in PC-3ML caused reduced cell proliferation, decreased levels of phosphorylated AKT, G(0)-G(1) arrest, and increased apoptosis and caspase-3 activity. Suppression of COX-2 increased Bax protein and decreased Bcl-x(L) protein in vitro. COX-2 antisense-expressing PC-3ML tumors showed a 57% growth delay compared with nontransfected or vector controls. Oral administration of COL-3 (40 mg/kg, oral gavage) or Taxotere (2.3 mg/kg, intraperitoneally; 3x per week) in tumor-bearing mice further slowed tumor growth (65% and approximately 94%, respectively). Compared with the control group, the occurrence of apoptosis in antisense COX-2 tumors was eight times higher, and the tumor microvessel density was three times lower. CONCLUSIONS: These results provide direct evidence that constitutive expression of COX-2 in prostate cancer has both angiogenic and cytoprotective functions. Suppression of tumor cell COX-2 is sufficient to enhance chemotherapy response in prostate cancer.

Fruits, vegetables, and micronutrients in relation to breast cancer modified by menopause and hormone receptor status.

Whether fruit, vegetable, and antioxidant micronutrient consumption is associated with a reduction in breast cancer incidence remains unresolved. To address this issue, we analyzed data from a large population-based case-control study, with consideration given to whether the associations varied with menopausal status or with clinical characteristics of the cases' disease. Study participants completed a modified Block food frequency questionnaire, which included assessment of the frequency and portion sizes of 13 fruits and fruit juices and 16 vegetables and the use of multiple and single vitamin supplements. Statistical analyses were done on 1,463 cases and 1,500 controls. Among postmenopausal women, reduced odds ratios [OR; 95% confidence intervals (95% CI)] were noted for the highest fifth, as compared with the lowest fifth, of intake of any vegetables [0.63 (0.46-0.86); P for trend < 0.01] and leafy vegetables [0.66 (0.50-0.86); P for trend = 0.03] after controlling for age and energy intake. Adjusted ORs (95% CIs) were also decreased for postmenopausal breast cancer in relation to high intake of carotenoids, alpha-carotene, beta-carotene, lutein, and particularly lycopene [0.66 (0.48-0.90); P for trend = 0.03]. Inverse associations for fruits and vegetables were stronger for postmenopausal women with estrogen receptor (ER)+ tumors (OR, 0.65; 95% CI, 0.51-0.82) than ER- tumors (OR, 0.92; 95% CI, 0.64-1.32), but results were less consistent for micronutrients. No similarly reduced associations were observed among premenopausal women. ORs did not appreciably differ by in situ or invasive breast cancer or by whether cases had begun chemotherapy. Our results support an inverse association for fruit and vegetable intake among postmenopausal but not premenopausal breast cancer, which may be more pronounced among women with ER+ tumors.

The differential anti-proliferation effect of white (Pueraria mirifica), red (Butea superba), and black (Mucuna collettii) Kwao Krua plants on the growth of MCF-7 cells.

The differential anti-proliferation effect of white (Pueraria mirifica), red (Butea superba) and black (Mucuna collettii) Kwao Krua plant extracts on the growth of MCF-7 cells was evaluated after 4 days of incubation. The percent cell growth comparison was based on protein determination of the harvested cells in parallel with the control group and Pueraria lobata treatment group. Pueraria lobata led to no proliferation and a mild anti-proliferation effect on the growth of MCF-7 cells. Pueraria mirifica caused proliferation at 1 microg/mL and an anti-proliferative effect on the growth of MCF-7 cells at 100 and 1000 microg/mL with an ED50 value of 642.83 microg/mL. Butea superba led to no proliferation and an anti-proliferation effect on the growth of MCF-7 cells at 10, 100 and 1000 microg/mL with an ED50 value of 370.91 microg/mL. Mucuna collettii led to no proliferation and an anti-proliferation effect on the growth of MCF-7 cells at 100 and 1000 microg/mL with an ED50 value of 85.36 microg/mL. The results demonstrated that only Pueraria mirifica showed an estrogenic effect on MCF-7 cell growth and a clear antagonistic effect with E2 at high concentration. Butea superba and Mucuna collettii exhibited only anti-proliferation effects on the growth of MCF-7 cells in relation with a possible anti-estrogen mechanism or a potent cytotoxic effect.

Endocrine disrupters and menopausal health.

Chemicals known to disrupt the endocrine system of animal models are assessed for their potential impact on the health of menopausal and postmenopausal women. These "endocrine disrupters" consist of two groups of compounds - man-made and naturally occurring. There is some evidence to suggest that the naturally occurring phytoestrogens, derived from plant material, may have some beneficial effects on menopausal symptoms and the risk of breast cancer, cardiovascular disease and osteoporosis. Further studies are required to confirm these possibilities. Some man-made environmental pollutants appear to increase the risk of breast cancer, although again the evidence is inconclusive. Mechanistic experiments indicate that these chemicals interact with oestrogen receptors and alter metabolism in a number of different ways, some of which may be important in postmenopausal women. Further investigation of the differences in mode of action between the man-made and the natural endocrine disrupters may lead to important insights into their effects on women's health.

Phyto-oestrogens and breast cancer chemoprevention.

Phytoestrogens are polyphenol compounds of plant origin that exhibit a structural similarity to the mammalian steroid hormone 17beta-oestradiol. In Asian nations the staple consumption of phyto-oestrogen-rich foodstuffs correlates with a reduced incidence of breast cancer. Human dietary intervention trials have noted a direct relationship between phyto-oestrogen ingestion and a favourable hormonal profile associated with decreased breast cancer risk. However, these studies failed to ascertain the precise effect of dietary phyto-oestrogens on the proliferation of mammary tissue. Epidemiological and rodent studies crucially suggest that breast cancer chemoprevention by dietary phyto-oestrogen compounds is dependent on ingestion before puberty, when the mammary gland is relatively immature. Phyto-oestrogen supplements are commercially marketed for use by postmenopausal women as natural and safe alternatives to hormone replacement therapy. Of current concern is the effect of phyto-oestrogen compounds on the growth of pre-existing breast tumours. Data are contradictory, with cell culture studies reporting both the oestrogenic stimulation of oestrogen receptor-positive breast cancer cell lines and the antagonism of tamoxifen activity at physiological phyto-oestrogen concentrations. Conversely, phyto-oestrogen ingestion by rodents is associated with the development of less aggressive breast tumours with reduced metastatic potential. Despite the present ambiguity, current data do suggest a potential benefit from use of phyto-oestrogens in breast cancer chemoprevention and therapy. These aspects are discussed.