The role of soy phytoestrogens in prostate cancer

A review on protective role of genistein against oxidative stress in diabetes and related complications

Diabetes mellitus (DM) is metabolism related problems that share the phenotype of hyperglycemia, which is triggered by a complicated interaction of hereditary and environmental elements. It is the main reason for end-stage renal disease (ESRD), amputations of the traumatic lower extremity, and grown-up visual impairment. It additionally inclines to neurodegenerative and cardiovascular sicknesses. With an expanding rate around the world, DM may be the main motive of morbidity and mortality within the foreseeable future. The objective of treatment for DM is to inhibit mortality and difficulties through normalizing blood glucose stage. Genistein, a naturally available soy isoflavone, is accounted for to have various medical advantages credited to numerous natural capacities. In the course of recent years, various examinations have shown that genistein has hostile to diabetic impacts, specifically, direct consequences for β-cell expansion, glucose-triggered insulin discharge, and safety towards apoptosis, unbiased of its functions as an estrogen receptor agonist, cancer prevention agent, or tyrosine kinase inhibitor. The present evaluation emphases on the promising molecular and biochemical paths associated with DM complications and, specifically, the multi-target method of genistein in diminishing diabetic neuropathy, nephropathy, and retinopathy.

Impact of food matrix on isoflavone metabolism and cardiovascular biomarkers in adults with hypercholesterolemia

The role of food matrix and gender on soy isoflavone metabolism and biomarkers of activity were examined in twenty free-living adults (34.7 ± 11.5 years old) with hypercholesterolemia (221.9 ± 18.7mg dL(-1)). In a randomized crossover design study, participants consumed soy bread (3 wk) or a soy beverage (3 wk) containing 20 g soy protein with 99 and 93 mg isoflavones aglycone equivalents per day, respectively. During soy bread intervention, women had significantly greater microbial metabolite excretion (P = 0.05) of isoflavonoids than men. In men, isoflavone metabolite excretion was not discernibly different between the two matrices. Significant reductions (P≤ 0.05) in triglycerides (24.8%), LDL cholesterol (6.0%), apolipoprotein A-I (12.3%), and lipid oxidative stress capacity (25.5%), were observed after soy food intervention. Our findings suggest that the food matrix significantly impacts soy isoflavone metabolism, particularly microbial metabolites in women.

Neonatal exposure to genistein adversely impacts the ontogeny of hypothalamic kisspeptin signaling pathways and ovarian development in the peripubertal female rat

Neonatal exposure to estrogenic endocrine disrupting compounds (EDCs) can advance pubertal onset and induce premature anestrous in female rats. It was recently discovered that hypothalamic kisspeptin (KISS) signaling pathways are sexually dimorphic and regulate both the timing of pubertal onset and estrous cyclicity. Thus we hypothesized that disrupted sex specific ontogeny of KISS signaling pathways might be a mechanism underlying these EDC effects. We first established the sex specific development of KISS gene expression, cell number and neural fiber density across peripuberty in the anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC), hypothesizing that the sexually dimorphic aspects of KISS signaling would be most vulnerable to EDCs. We next exposed female rats to the phytoestrogen genistein (GEN, 1 or 10 mg/kg bw), estradiol benzoate (EB, 10 μg), or vehicle from post natal day (P) 0-3 via subcutaneous (sc) injection. Animals were sacrificed on either P21, 24, 28, or 33 (n=5-14 per group at each age). Vaginal opening was significantly advanced by EB and the higher dose of GEN compared to control animals and was accompanied by lower numbers of KISS immunoreactive fibers in the AVPV and ARC. Ovarian morphology was also assessed in all age groups for the presence of multiple oocyte follicles (MOFs). The number of MOFs decreased over time in each group, and none were observed in control animals by P24. MOFs were still present, however, in the EB and 10 mg/kg GEN groups beyond P24 indicating a disruption in the timing of ovarian development.

Clinical pharmacology of isoflavones and its relevance for potential prevention of prostate cancer

Isoflavones are phytoestrogens that have pleiotropic effects in a wide variety of cancer cell lines. Many of these biological effects involve key components of signal transduction pathways within cancer cells, including prostate cancer cells. Epidemiological studies have raised the hypothesis that isoflavones may play an important role in the prevention and modulation of prostate cancer growth. Since randomized phase III trials of isoflavones in prostate cancer prevention are currently lacking, the best evidence for this concept is presently provided by case control studies. However, in vitro data are much more convincing in regard to the activity of a number of isoflavones, and have led to the development of genistein and phenoxodiol in the clinic as potential treatments for cancer. In addition, the potential activity of isoflavones in combination with cytotoxics or radiotherapy warrants further investigation. This review focuses on the clinical pharmacology of isoflavones and its relevance to their development for use in the prevention of prostate cancer, and it evaluates some of the conflicting data in the literature.

Androgen-Deprivation Therapy in Prostate Cancer: Clinical Evidence and Future Perspectives

Androgens are involved in the development and progression of prostate cancer even if the mechanism is not well-recognized. For this reason androgen-deprivation therapy remains a milestone for the treatment of patients with advanced and metastatic disease and, in the last years, in conjunction with radiotherapy and surgery in locally advanced tumors. Alternative options, such as intermittent deprivation suppression, seem to be promising in terms of clinical benefits and toxicity profile. However, current therapies present side effects, such as testosterone surge with consequent clinical flare-up, metabolic syndrome and hormone-resistance, which develops after a variable number of years. Novel therapies such as LH-RH antagonists and prolonged depot LH-RH analogues have been developed in order to avoid clinical flare-up and testosterone microsurges. Novel androgen synthesis inhibitors, such as abiraterone acetate and MDV3100, have been recently discovered and tested as promising hormonal second-line agents in patients with castration-resistant prostate cancer. Finally, long-term side effects from androgen deprivation, such as osteoporosis, sarcopenic obesity and cardiovascular morbidity should be carefully monitored and properly treated.

Molecular and biochemical effects of a kola nut extract on androgen receptor-mediated pathways

The low incidence of prostate cancer in Asians has been attributed to chemopreventative properties of certain chemicals found in their diet. This study characterized the androgenic and chemopreventative properties of the Jamaican bush tea “Bizzy,” using androgen receptor positive and negative cell lines. Exposure of prostate cells to Biz-2 resulted in a growth inhibition (GI₅₀) of 15 ppm in LNCaP cells and 3.6 ppm in DU145 cells. Biz-2 elicited a 2-fold increase in the mRNA of the anti-apoptotic gene Bcl2, with a 10-fold increase in that of the proapoptotic gene Bax. We observed a 2.4- to 7.5-fold change in apoptotic cells in both cell lines. Biz-2 at 10 ppm elicited a time- and dose-dependent stimulation of both the protein and mRNA levels of several androgen-regulated genes. Biz-2 caused a 36% decrease in PSA secretion and a significant increase in PSA mRNA. The relative binding affinity (IC₅₀) of Biz-2 for AR was 2- to 5-fold lower than that of the synthetic androgen R1881. Biz-2 was found to be a specific ligand for the AR in that the natural ligand, DHT, and the anti-androgen, flutamide, displaced Biz-2 bound to AR and inhibited Biz-2-induced transcription and PSA secretion. This study provided evidence that Biz-2 extract possesses the ability to modulate prostate cancer cell biology in an AR-dependent manner.

Soy, isoflavones, and prostate cancer

Prostate cancer has marked geographic variations between countries. Genetic, epigenetic, and environmental factors co-contribute to the development of the cancer. The association between dietary factors and prostate cancer has been investigated and one explanation for the low incidence of the cancer in Asia might be high consumption of fresh vegetables including soybean and its products. Soybean is a species of legume contain high amount of isoflavones including genistein, daidzein, glycitein, and equol, which have a prophylactic effect on prostate cancer. In this article, epidemiological and laboratory studies on the relationship between soybeans, isoflavones and prostate cancer are reviewed and large scale multiethnic epidemiological studies are recommended.

Legume and isoflavone intake and prostate cancer risk: The Multiethnic Cohort Study

Findings from studies of legume, soy and isoflavone intake and prostate cancer risk are as yet inconclusive, although soy has received considerable attention due to its high phytoestrogen content. Therefore, the present study investigated the relationship of these dietary exposures to prostate cancer risk in the Multiethnic Cohort Study in Hawaii and Los Angeles. The analyses included 82,483 men who completed a detailed quantitative food frequency questionnaire in 1993-1996. A total of 4,404 prostate cancer cases including 1,278 nonlocalized or high-grade cases were recorded during the average follow-up period of 8 years. Multivariate relative risks (RR) and 95% of confidence intervals (CI) were estimated using Cox proportional hazards models with age as the time metric. Among men with the highest intake of legumes, the risk reduction was 11% for total prostate cancer (RR = 0.89, 95% CI = 0.80-0.99, p for trend = 0.007) and 26% for nonlocalized or high-grade cancer (RR = 0.74, 95% CI = 0.61-0.90, p for trend = 0.007) compared to men with the lowest intake. Similar risk reductions were observed for soy products and for legumes excluding soy products in separate analyses. We found no significant risk reduction associated with intake of total or specific isoflavones for either total prostate cancer or for nonlocalized or high-grade cancer. The findings of our study suggest that legume intake is associated with a moderate reduction in prostate cancer risk and that the isoflavones in soy products are probably not responsible for this effect.

Phytoestrogens: perpetrators or protectors?

Phytoestrogens are estrogen-like substances produced by plants that account for some of the constituents present in vegetation that may be responsible for the health benefits of a diet rich in fruit and vegetables. Phytoestrogens have a plethora of different actions that they are capable of exerting on cellular metabolism. This review will focus on some of the major non-estrogen receptor-mediated cellular effects used by phytoestrogens and will draw attention to the fact that while they may have a number of beneficial effects, particularly in offering a protective effect against some hormone-dependent cancers, such as breast and prostate cancer, they may also have possible unfavorable effects by interfering with the functioning of normal cellular activities such as receptor-mediated signal transduction and DNA replication, as well as being genotoxic, mutagenic and promoting the proliferation of some cancer cells.

Database of traditional Chinese medicine and its application to studies of mechanism and to prescription validation

BACKGROUND AND PURPOSE

Traditional Chinese Medicine (TCM) is widely practised and is viewed as an attractive alternative to conventional medicine. Quantitative information about TCM prescriptions, constituent herbs and herbal ingredients is necessary for studying and exploring TCM.

EXPERIMENTAL APPROACH

We manually collected information on TCM in books and other printed sources in Medline. The Traditional Chinese Medicine Information Database TCM-ID, at http://tcm.cz3.nus.edu.sg/group/tcm-id/tcmid.asp, was introduced for providing comprehensive information about all aspects of TCM including prescriptions, constituent herbs, herbal ingredients, molecular structure and functional properties of active ingredients, therapeutic and side effects, clinical indication and application and related matters.

RESULTS

TCM-ID currently contains information for 1,588 prescriptions, 1,313 herbs, 5,669 herbal ingredients, and the 3D structure of 3,725 herbal ingredients. The value of the data in TCM-ID was illustrated by using some of the data for an in-silico study of molecular mechanism of the therapeutic effects of herbal ingredients and for developing a computer program to validate TCM multi-herb preparations.

CONCLUSIONS AND IMPLICATIONS

The development of systems biology has led to a new design principle for therapeutic intervention strategy, the concept of 'magic shrapnel' (rather than the 'magic bullet'), involving many drugs against multiple targets, administered in a single treatment. TCM offers an extensive source of examples of this concept in which several active ingredients in one prescription are aimed at numerous targets and work together to provide therapeutic benefit. The database and its mining applications described here represent early efforts toward exploring TCM for new theories in drug discovery.

BRCA1 and BRCA2 as molecular targets for phytochemicals indole-3-carbinol and genistein in breast and prostate cancer cells

Indole-3-carbinol (I3C) and genistein are naturally occurring chemicals derived from cruciferous vegetables and soy, respectively, with potential cancer prevention activity for hormone-responsive tumours (e.g., breast and prostate cancers). Previously, we showed that I3C induces BRCA1 expression and that both I3C and BRCA1 inhibit oestrogen (E2)-stimulated oestrogen receptor (ER-α) activity in human breast cancer cells. We now report that both I3C and genistein induce the expression of both breast cancer susceptibility genes (BRCA1 and BRCA2) in breast (MCF-7 and T47D) and prostate (DU-145 and LNCaP) cancer cell types, in a time- and dose-dependent fashion. Induction of the BRCA genes occurred at low doses of I3C (20 μM) and genistein (0.5–1.0 μM), suggesting potential relevance to cancer prevention. A combination of I3C and genistein gave greater than expected induction of BRCA expression. Studies using small interfering RNAs (siRNAs) and BRCA expression vectors suggest that the phytochemical induction of BRCA2 is due, in part, to BRCA1. Functional studies suggest that I3C-mediated cytoxicity is, in part, dependent upon BRCA1 and BRCA2. Inhibition of E2-stimulated ER-α activity by I3C and genistein was dependent upon BRCA1; and inhibition of ligand-inducible androgen receptor (AR) activity by I3C and genistein was partially reversed by BRCA1-siRNA. Finally, we provide evidence suggesting that the phytochemical induction of BRCA1 expression is due, in part, to endoplasmic reticulum stress response signalling. These findings suggest that the BRCA genes are molecular targets for some of the activities of I3C and genistein.

Role of vitamins, minerals and supplements in the prevention and management of prostate cancer

The authors review the current literature on the complementary and alternative medicines most frequently utilized by prostate cancer patients and those at risk for the disease. Products covered are vitamin E, vitamin A, selenium, zinc, soy, lycopene, pomegranate juice, green tea and omega-3 fatty acids. There is no definitive proof that any of the nutritional supplements discussed can impact the course of prostate cancer or its development. The authors believe that simply taking a standard daily multivitamin should be sufficient to ensure that patients have the appropriate levels of vitamins and minerals without risking the over utilization of vitamins, minerals, and supplements which can lead to numerous negative side effects.

Complementary and alternative medicine in urology

Complementary and alternative medicine (CAM) includes various practices, measures and products which are not presently considered to be a part of conventional (mainstream) medicine. Herbal products, vitamins, minerals and amino acids are increasingly popular as dietary supplements for the treatment, improvement and prophylaxis of urological diseases, and to improve general health and well-being. As these products are freely available without prescription, conventional healthcare providers are often unaware that their patients are using CAM. It is essential to know that some herbal supplements may act in the same way as chemical drugs, and that they originate 'from nature' does not mean that they are safe and/or with no potential harmful effects and/or toxicity. Eventual interactions with conventional medications and contamination with prescription drugs and metals have been reported. The active components of many phytotherapeutic preparations and their mechanism(s) of action are still being determined and evaluated. There is scientific evidence for the effectiveness of some CAM treatments, but for most there are important key questions yet to be answered through basic research and well-designed studies according to established guidelines. Because of the increasing popularity and use of CAM, conventional healthcare providers, including urologists, should not ignore it, and be well informed about the benefits and potential risks of dietary supplements, so that they can advise their patients about this developing field. Whenever necessary and possible, lifestyle and behavioural changes should be recommended before using CAM, and eventually be supplemented by CAM as a second step.

Novel antiproliferative flavonoids induce cell cycle arrest in human prostate cancer cell lines

Epidemiologic studies have demonstrated an inverse association between flavonoid intake and prostate cancer (PCa) risk. The East Asian diet is very high in flavonoids and, correspondingly, men in China and Japan have the lowest incidence of PCa worldwide. There are thousands of different naturally occurring and synthetic flavonoids. However, only a few have been studied in PCa. Our aim was to identify novel flavonoids with antiproliferative effect in PCa cell lines, as well as determine their effects on cell cycle. We have screened a representative subgroup of 26 flavonoids for antiproliferative effect on the human PCa (LNCaP and PC3), breast cancer (MCF-7), and normal prostate stromal cell lines (PrSC). Using a fluorescence-based cell proliferation assay (Cyquant), we have identified five flavonoids, including the novel compounds 2,2'-dihydroxychalcone and fisetin, with antiproliferative and cell cycle arresting properties in human PCa in vitro. Most of the flavonoids tested exerted antiproliferative effect at lower doses in the PCa cell lines compared to the non-PCa cells. Flow cytometry was used as a means to determine the effects on cell cycle. PC3 cells were arrested in G2/M phase by flavonoids. LNCaP cells demonstrated different cell cycle profiles. Further studies are warranted to determine the molecular mechanism of action of 2,2'-DHC and fisetin in PCa, and to establish their effectiveness in vivo.

Administration of extract of mushroom Phellinus linteus induces prostate enlargement with increase in stromal component in experimentally developed rat model of benign prostatic hyperplasia

OBJECTIVES

To clarify the effect of the mushroom extract Phellinus linteus on noncancerous prostate cells using an experimentally developed rat benign prostatic hyperplasia model. A growing number of people take some natural herbal extracts for maintenance of their health. Among them, the extracts of certain mushrooms are believed to have a marked tumoricidal effect but low toxicity for normal tissues, and they are being drunk widely in Japan and Korea. However, until now, their effect on noncancerous benign prostate growth has not been examined.

METHODS

The mushroom extract was administered daily for 5 weeks to experimentally developed benign prostatic hyperplasia rats. Prostate organ weight, histologic composition, and gene expression levels of sex hormone receptors, transforming growth factor-beta, vascular endothelial growth factor, and endothelial nitric oxide synthase were examined.

RESULTS

Prostate weight increased significantly by 37% owing to treatment with the mushroom extract (P < 0.05). In particular, the stromal component of the prostate increased significantly by 80% (P < 0.05). A suppression of transforming growth factor-beta1 expression by 56% was observed with the mushroom extract treatment (P < 0.05).

CONCLUSIONS

We found that the mushroom extract enlarged the prostate. The effect was suggested to be on the prostate stroma, which may be involved in transforming growth factor-beta1 regulation. Administration of mushroom extract should be considered carefully by those with an enlarged prostate.

Phytoestrogens and prostate cancer risk

BACKGROUND

Phytoestrogens are natural plant substances. The four main classes are isoflavones, flavonoids, coumestans, and lignans. Phytoestrogens have anti-carcinogenic potential. For evaluation of the effect of phytoestrogens on prostate cancer risk, we reviewed analytical epidemiological data.

METHODS

Up to now, there are few studies that have assessed the direct relation between the individual dietary intake of soy products and other nutrients with phytoestrogens and the risk of prostate cancer. We decided to review analytical epidemiological studies providing data on (a) dietary soy intake or flavonoids intake, (b) urinary excretion of isoflavones or lignans, or (c) blood measurements of isoflavones or lignans. Soy is used as a marker for isoflavone intake.

RESULTS

Overall, the results of these studies do not show protective effects. Only four of these studies are prospective, and none of them found statistically significant prostate cancer reductions. Two prospective studies measured flavonoid intake and one reported a preventive effect on prostate cancer for the assumption of myricetin. One study assessed enterolactone concentrations in three different countries and showed no reduction in prostate cancer occurrence.

CONCLUSION

Few studies showed protective effect between phytoestrogen intake and prostate cancer risk.

Blocking effects of genistein on cell proliferation and possible mechanism in human gastric carcinoma

AIM: To study the blocking effects of genistein on cell proliferation cycle in human gastric carcinoma cells (SGC-7901) and the possible mechanism.

METHODS: MTT assay was applied in the detection of the inhibitory effects of genistein on cell proliferation. Flow cytometry was used to analyze the cell cycle distribution. Immunocytochemical technique and Western blotting were performed to detect the protein expression of cyclin D₁, cyclin B₁ and p21^waf1/cip1.

RESULTS: Genistein significantly inhibited the growth and proliferation of human gastric carcinoma cells (SGC-7901). Seven days after treatment with different concentrations of genistein (2.5, 5.0, 10.0, 20.0 μg /mL), the growth inhibitory rates were 11.2%, 28.8%, 55.3%, 84.7% respectively and cell cycles were arrested at the G(2)/ M phase. Genistein decreased cyclin D₁ protein expression and enhanced cyclin B₁ and p21waf/cip1 protein expression in a concentration-dependent manner.

CONCLUSION: The growth and proliferation of SGC-7901 cells can be inhibited by genistein via blocking the cell cycle, with reduced expression of cyclin D₁ and enhanced expression of cyclin B₁ and p21waf/cip1 protein in the concentration range of 0-20 μg /mL.

Genistein affects androgen-responsive genes through both androgen- and estrogen-induced signaling pathways

This study examined the mechanisms by which the prostate cancer chemopreventive agent genistein modulates gene expression in LNCaP human prostate cancer cells. Expression of androgen- and estrogen-regulated genes was measured in LNCaP cells cultured in the presence or absence of hormonal stimulation and the presence or absence of genistein. Genistein strongly suppressed basal expression of androgen-responsive gene (ARG) mRNAs, including prostate-specific antigen (PSA) and Ste20-related proline-alanine-rich kinase (SPAK). However, genistein had little or no effect on basal expression of two other ARGs, beta2-microglobulin (B2M) or selenoprotein P (SEPP1). Culturing LNCaP cells in the presence of the synthetic androgen R1881-induced increases in PSA, SPAK, B2M, and SEPP1 mRNA levels. The R1881-induced expression of these genes was uniformly blocked by genistein. For PSA and SPAK, genistein also blocked or downregulated 17beta-estradiol-induced increases in mRNA expression. These results indicate that genistein selectively alters expression of ARG mRNAs in LNCaP cells through modulation of both androgen- and estrogen-induced signaling pathways.

Androgen deprivation therapy for prostate cancer: current status and future prospects

Androgens play a major role in promoting the development and progression of prostate cancer. As a result, androgen ablation or blockade of androgen action through the androgen receptor (AR) has been the cornerstone of treatment of advanced prostate cancer. Different strategies involving this hormonal therapy produce a significant clinical response in most of the patients, but most responders eventually lose dependency, resulting in mortality. Thus, whether hormonal therapy contributes to the improvement of overall survival rates, especially in patients with advanced prostate cancer, remains controversial. However, patients with advanced disease clearly have a benefit from androgen deprivation-based treatment for palliating their symptoms and for improving the quality of their lives. In order to improve overall survival, novel treatment strategies that prolong the androgen-dependent state and that are useful for androgen-independent disease based on specific molecular mechanisms need to be identified.

Identification of flavonoids in Hakmeitau beans (Vigna sinensis) by high-performance liquid chromatography-electrospray mass spectrometry (LC-ESI/MS)

Liquid chromatography coupled with electrospray mass spectrometry (LC-ESI/MS) with positive and negative ion detection was used for the identification of flavonoids in Hakmeitau beans, a black seed cultivar of cowpea (Vigna sinensis). Gradient elution with water and acetonitrile, both containing 2% formic acid, was employed in chromatographic separation. The peaks were identified by comparison of the retention times and the UV-vis spectroscopic and mass spectrometric data with authentic standards and/or literature data. The identified flavonoids included six anthocyanins (cyanidin 3-O-galactoside, cyanidin 3-O-glucoside, delphinidin 3-O-glucoside, malvidin 3-O-glucoside, peonidin 3-O-glucoside, and petunidin 3-O-glucoside) and four flavonol/flavonol glycosides (kaempferol 3-O-glucoside, quercetin, quercetin 3-O-glucoside, and quercetin 3-O-6' '-acetylglucoside). The tentatively identified flavonoids included two anthocyanins (malvidin 3-O-acetylglucoside and peonidin 3-O-malonylglucoside) and three flavonol glycosides (myricetin-3-O-glucoside, quercetin 7-O-glucoside, and quercetin-3-O-diglucoside). These flavonoids are present in seed coats, and the contents of anthocyanins and flavonol glycosides were 20.7 and 2.0 mg/g, respectively.

Using DNA microarray analyses to elucidate the effects of genistein in androgen-responsive prostate cancer cells: identification of novel targets

Many studies have correlated the consumption of soy-rich diets with a decreased risk of developing hormone-dependent cancers, including prostate cancer. Genistein is a candidate prostate cancer preventive phytochemical found at high levels in soybean and soy foods. To better understand the molecular mechanisms underlying the beneficial effects of genistein on prostate cancer prevention, we used a DNA microarray approach to examine the effects of genistein at concentrations in the physiologic range on global gene expression patterns in androgen-responsive cancer cells. Microarray analyses were performed on androgen-responsive LNCaP human prostate cancer cells exposed to 0, 1, 5, or 25 microM genistein. We found a concentration-dependent modulation of multiple cellular pathways that are important in prostate carcinogenesis. Interestingly, the androgen receptor (AR)-mediated pathways, in particular, appeared to be modulated by genistein at the lowest concentrations. Based on these results, we propose that the regulation of AR-mediated pathways is potentially the most relevant chemopreventive mechanism for genistein administered at physiologic levels.

A Multicountry Ecologic Study of Risk and Risk Reduction Factors for Prostate Cancer Mortality

OBJECTIVE

The objective of this research is to identify and determine the relative importance of dietary and environmental risk and risk reduction factors for prostate cancer mortality.

MATERIALS AND METHODS

A multicountry ecologic approach was used in multivariate regression analyses with prostate cancer mortality rates and dietary factors and solar ultraviolet-B (UV-B) radiation. Prostate cancer mortality rates for 32 predominantly Caucasian countries for the late 1990s were obtained from the World Health Organization. Dietary supply data were obtained from the Food and Agriculture Organization. Annual solar UV-B dose data were obtained from European ground stations and used to estimate values elsewhere. Linear and multiple linear regression analyses were conducted for all 32 countries as well as the 20 European countries.

RESULTS

The strongest risk factor for prostate cancer mortality was animal products, with the nonfat portion of milk and alcohol being somewhat weaker; the strongest risk reduction factors were onions, other protective vegetable products (excluding alcohol, oils, and sweeteners), and solar UV-B radiation. Dietary data for 1979-81 yielded the highest correlations.

CONCLUSIONS

These results are consistent with insulin-like growth factor-I (IGF-I), being an important risk factor for prostate cancer, with alcohol and calcium being less important risk factors, and with allium family vegetables, and, to a lesser extent, vitamin D being important risk reduction factors. These results should provide guidance for additional studies on dietary and environmental links to prostate cancer.

Follow-up of conservatively managed prostate cancer: watchful waiting and primary hormonal therapy

Many men with newly diagnosed prostate cancer choose not to undergo curative treatment, including patients who cannot be helped by local curative therapies (especially those with metastatic disease) and patients with clinically localized disease who opt for expectant management or noncurative treatments such as androgen ablation. This article reviews the selection of patients for these noncurative approaches, strategies for clinical monitoring, the choices of intervention therapies upon progression, and when to start these therapies.

Clinical characteristics and pharmacokinetics of purified soy isoflavones: multiple-dose administration to men with prostate neoplasia

A phase I clinical trial was conducted to determine the safety, pharmacokinetic parameters, and efficacy of orally administered isoflavones (genistein and daidzein, potential cancer chemotherapeutic agents) over a 3-mo period in men with prostate neoplasia. Twenty men, ages 40 and above, with stage B, C, or D adenocarcinoma of the prostate were treated with a multiple-dose regimen of a soy isoflavone formulation (delivering approximately 300 or 600 mg/day genistein and half this much daidzein) for 84 days. The delivered dose of isoflavones was more than 10-fold higher than that typically taken by prostate cancer patients. In men with prostate cancer, relatively minor side effects of chronic isoflavone treatment were observed including some estrogenic effects (breast changes, increased frequency of hot flashes). Serum dehydroepiandrosterone was decreased by 31.7% (P = 0.0004) at the end of treatment. Except for those subjects whose prostate-specific antigen (PSA) values were below 0.4 ng/ml, subjects had a history of increasing PSA levels prior to the trial. This increase continued during the trial both while on soy isoflavones and after treatment was discontinued. On average the rate of rise accelerated after soy isoflavones were discontinued, but that difference did not attain statistical significance. Genistein and daidzein were rapidly cleared from plasma and excreted in urine. Pharmacokinetic data for chronic dose administration were similar to single-dose administration for the isoflavones investigated except that we observed slightly longer circulation time for daidzein.

Estrogens and anti-estrogens: Key mediators of prostate carcinogenesis and new therapeutic candidates

Despite the historical use of estrogens in the treatment of prostate cancer (PCa) little is known about their direct biological effects on the prostate, their role in carcinogenesis, and what mechanisms mediate their therapeutic effects on PCa. It is now known that estrogens alone, or in synergism with an androgen, are potent inducers of aberrant growth and neoplastic transformation in the prostate. The mechanisms of estrogen carcinogenicity could be mediated via induction of unscheduled cell proliferation or through metabolic activation of estrogens to genotoxic metabolites. Age-related changes and race-/ethnic-based differences in circulating or locally formed estrogens may explain differential PCa risk among different populations. Loss of expression of estrogen receptor (ER)-beta expression during prostate carcinogenesis and prevention of estrogen-mediated oxidative damage could be exploited in future PCa prevention strategies. Re-expression of ER-beta in metastatic PCa cells raises the possibility of using ER-beta-specific ligands in triggering cell death in these malignant cells. A variety of new estrogenic/anti-estrogenic/selective estrogen receptor modulator (SERM)-like compounds, including 2-methoxyestradiol, genistein, resveratrol, licochalcone, Raloxifene, ICI 182,780, and estramustine are being evaluated for their potential in the next generation of PCa therapies. Increasing numbers of patients self-medicate with herbal formulations such as PC-SPES. Some of these compounds are selective ER-beta ligands, while most of them have minimal interaction with ER-alpha. Although many may inhibit testosterone production by blockade of the hypothalamal-pituitary-testis axis, the most effective agents also exhibit direct cytostatic, cytotoxic, or apoptotic action on PCa cells. Some of them are potent in interfering with tubulin polymerization, blocking angiogenesis and cell motility, suppressing DNA synthesis, and inhibiting specific kinase activities. Further discovery of other compounds with potent apoptotic activities but minimal estrogen action should promote development of a new generation of effective PCa preventive or treatment regimens with few or no side-effects due to estrogenicity. Further advancement of our knowledge of the role of estrogens in prostate carcinogenesis through metabolic activation of estrogens and/or ER-mediated pathways will certainly result in better preventive or therapeutic modalities for PCa.

In vitro metabolism of genistein and tangeretin by human and murine cytochrome P450s

Recombinant cytochrome P450 (CYP) 1A2, 3A4, 2C9 or 2D6 enzymes obtained from Escherichia coli and human liver microsomes samples were used to investigate the ability of human CYP enzymes to metabolize the two dietary flavonoids, genistein and tangeretin. Analysis of the metabolic profile from incubations with genistein and human liver microsomes revealed the production of five different metabolites, of which three were obtained in sufficient amounts to allow a more detailed elucidation of the structure. One of these metabolites was identified as orobol, the 3'-hydroxylated metabolite of genistein. The remaining two metabolites were also hydroxylated metabolites as evidenced by LC/MS. Orobol was the only metabolite formed after incubation with CYP1A2. The two major product peaks after incubation of tangeretin with human microsomes were identical with 4'-hydroxy-5,6,7,8-tetramethoxyflavone and 5,6-dihydroxy-4',7,8-trimethoxyflavone, previously identified in rat urine in our laboratory. By comparison with UV spectra and LC/MS fragmentation patterns of previously obtained standards, the remaining metabolites eluting after 14, 17 and 20 min. were found to be demethylated at the 4',7-, 4',6-positions or hydroxylated at the 3'- and demethylated at the 4'-positions, respectively. Metabolism of tangeretin by recombinant CYP1A2, 3A4, 2D6 and 2C9 resulted in metabolic profiles that qualitatively were identical to those observed in the human microsomes. Inclusion of the CYP1A2 inhibitor fluvoxamine in the incubation mixture with human liver microsomes resulted in potent inhibition of tangeretin and genistein metabolism. Other isozymes-selective CYP inhibitors had only minor effects on tangeretin or genistein metabolism. Overall the presented observations suggest major involvement of CYP1A2 in the hepatic metabolism of these two flavonoids.

Phase IIA Clinical Trial to Test the Efficacy and Safety of Toremifene in Men with High-Grade Prostatic Intraepithelial Neoplasia

Men with high-grade prostatic intraepithelial neoplasia (PIN) evident on prostate biopsy are at high risk for the eventual development of prostate cancer. The ability to reverse high-grade PIN may reduce the incidence or delay the development of prostate cancer. Toremifene (GTx-006, Acapodene trade mark ) is a selective estrogen receptor modulator that has been shown in the transgenic mouse model of prostate cancer to eliminate high-grade PIN and reduce the incidence of prostate cancer. This study was aimed at the evaluation of the safety and efficacy of toremifene in men diagnosed with high-grade PIN. This was an open-label, phase IIA clinical trial that enrolled 21 men (mean age, 64.7 years) with evidence of high-grade PIN on biopsy within 6 months of entry into the study. Eighteen of these men (86%) completed toremifene treatment (60 mg/day orally for 4 months) and then underwent follow-up prostate biopsy (8 cores) to determine high-grade PIN status. The effect of the drug on serum prostate-specific antigen (PSA), percentage of free PSA, testosterone, estradiol, and quality of life was also measured. After toremifene treatment, 72% of these 18 men (vs. 17.9% of historical controls) had no high-grade PIN on subsequent prostate biopsies. Mean PSA trended higher, and percentage of free PSA was increased. Quality of life was not significantly affected by treatment. There were 3 mild adverse events, and no serious adverse events. Toremifene appeared to reduce high-grade PIN in this small, exploratory trial. The drug was well tolerated. A double-blind, dose-finding, randomized, placebo-controlled phase IIB/III study is currently open to further study toremifene's activity against high-grade PIN and prostate cancer incidence.

Antiestrogens and selective estrogen receptor modulators reduce prostate cancer risk

The development of chemoprevention strategies against prostate cancer would have the greatest overall impact both medically and economically against prostate cancer. Estrogens are required for prostate carcinogenesis. Estrogenic stimulation through estrogen receptor alpha in a milieu of decreasing androgens contributes significantly to the genesis of benign prostatic hyperplasia, prostate dysplasia, and prostate cancer. The ability of antiestrogens and selective estrogen receptor modulators (SERMs) to delay and to suppress prostate carcinogenesis is supported by preclinical, clinical, and epidemiological studies. SERMs have many features that make them attractive candidates for prostate cancer chemoprevention including their favorable safety profile and efficacy in preclinical prostate cancer models. The true clinical benefits of SERMs for chemoprevention to prevent prostate cancer, however, should continue to be investigated through human clinical trials. A phase IIb/III human clinical trial is currently evaluating safety and efficacy of toremifene, a SERM, in men who have high-grade prostatic intraepithelial neoplasia.

Chemoprevention of prostate cancer

Dietary factors and other naturally occurring substances may emerge as potent therapeutic or preventative agents in the battle against prostate cancer. Much of the current support for these agents is epidemiologically based, but new prospective studies are now underway which may support their use in conventional medical practice.

Prostate Cancer Prevention: What Do We Know Now, and When Will We Know More?

Prostate cancer prevention is now one of the most aggressively investigated areas of urologic oncology, with > 30,000 men currently participating in clinical trials in the United States alone. The Prostate Cancer Prevention Trial will complete end-of-study prostate biopsies in May 2004, and the Selenium and Vitamin E Cancer Prevention Trial is rapidly reaching its accrual goal 1-2 years ahead of schedule. These 2 studies will give definitive answers regarding 3 of the most important potential preventive interventions: finasteride, vitamin E, and selenium. Many phase II and biomarker-modulation studies are also ongoing, testing a host of other interventions. It is hoped that, within a short period of time, the clinician will be provided with strategies to reduce the risk of the disease.

Determination of daidzein and genistein in soybean foods by automated on-line in-tube solid-phase microextraction coupled to high-performance liquid chromatography

An automated on-line method for the determination of the isoflavones, daidzein and genistein, was developed using in-tube solid-phase microextraction coupled to high-performance liquid chromatography (in-tube SPME-HPLC). In-tube SPME is a new extraction technique for organic compounds in aqueous samples, in which analytes are extracted from the sample directly into an open tubular capillary by repeated draw/eject cycles of sample solution. Daidzein, genistein and their glucosides tested in this study were clearly separated within 8 min by HPLC using an XDB-C8 column with diode array detection. In order to optimize the extraction of these compounds, several in-tube SPME parameters were examined. The glucosides daidzin and genistin were analyzed as aglycones after hydrolysis because the glucosides were not concentrated by in-tube SPME. The optimum extraction conditions for daidzein and genistein were obtained with 20 draw/eject cycles of 40 microl of sample using a Supel-Q porous layer open tubular capillary column. The extracted compounds were easily desorbed from the capillary by mobile phase flow, and carryover was not observed. Using the in-tube SPME-HPLC method, the calibration curves of these compounds were linear in the range 5-200 ng/ml, with a correlation coefficient above 0.9999 (n = 18), and the detection limits (S/N = 3) were 0.4-0.5 ng/ml. This method was successfully applied to the analysis of soybean foods without interference peaks. The recoveries of aglycones and glucosides spiked into food samples were above 97%.