| January 1998 |
Isoflavonoids in soy drinks and availability in human body fluids.
Increasing evidence suggests that soy consumption and/or soy isoflavones might protect against various cancers and against other chronic diseases such as osteoporosis and cardiovascular disorders. Epidemiologic studies concerned with the accurate assessment of the role of soy and isoflavones to prevent cancer require fast, reliable and affordable techniques to measure exposure favorably, through non-invasive protocols using biochemical markers. Therefore, we developed a rapid and accurate procedure to extract soy specific isoflavones from foods and from human plasma, urine, saliva and breast milk followed by selective HPLC quantitation using diode-array and electrochemical detection. Soy drinks known to be the main source of soy exposure in Western societies were found to contain isoflavones predominantly (70-90%) as their malonyl and glucoside conjugates. Total daidzein, genistein and glycitein levels varied between 90 and 370 mg/kg, 140 and 620 mg/kg, and 50 and 140 mg/kg, respectively. Similarly, up to fivefold inter-individual differences of isoflavone levels, in human fluids were observed after exposure to a given single soy serving. Isoflavonoid levels in plasma and other body fluids were found to be significantly correlated within an individual, suggesting that non-invasive protocols can be used in future epidemiologic studies evaluating the health benefits of soy foods and/or soy isoflavones.
Breast Cancer and Genistein
Programming against breast cancer with genistein, a component of soy.
Breast cancer is the most common cancer in females and is the second leading cause of cancer death among women. Yet, Asian women consuming a traditional diet high in soy products have a low incidence of breast cancer. Asians who emigrate to the United States and adopt a Western diet lose this protection. Using the imethylbenz(a) anthracene-mammary cancer rat model, we have investigated the potential of genistein, a phytoestrogen component of soy, to protect against the development of mammary cancer. Our results demonstrated that prepubertal genistein treatment resulted in decreased incidence and number of tumors per rat. Mammary whole mount analysis showed that genistein treatment resulted in mammary glands of adult rats developing fewer terminal end buds and more lobules. Cell proliferation studies with bromodeoxyuridine (BrdU) showed that terminal end buds from mammary glands of 50-day-old females treated with genistein had significantly fewer cells in S-phase of the cell cycle. In vivo mechanistic studies revealed that genistein and estrogen modulated tyrosine phosphorylation of the EGF-receptor. We conclude that genistein exerts its action via the estrogen receptor mechanism, that in turn sets in motion a cascade of down stream events to result in gland differentiation and less susceptibility for mammary cancer.
Inducing Cancer Cell Maturation
Induction of maturation of breast cancer cells by genistein.
Recent studies on animal models of mammary carcinogenesis identified the soybean isoflavone genistein as a chemopreventive agent. The objective of the present study is to determine if soybean isoflavones can be applied in the prevention of human breast carcinogenesis. Human adenocarcinoma cells that are either estrogen receptor-positive (ER+, such as MCF-7) or ER-negative ( ER-, such as MDA-MB-468) was used as our model system. Treatment of these cells with genistein Various concentrations resulted in cell growth inhibition, which was accompanied by the expression of maturation markers. Maturation was monitored by the induction of intra-cytoplasmic casein and lipids and the membrane protein l-CAM. Optimal expression of these maturation markers was after nine days of treatment with 30 micromolars of genistein. Both ER+ and ER- cells became differentiated in response to genistein treatments, suggesting that the anti-estrogenic function of genistein is unrelated to the mechanism of cell differentiation. Daidzein, the other major isoflavone component of soy, did not induce differentiation in either MCF-7 or MDA-MB-468 cells. To explore the potential applications of this observation, we used the nude mouse xenograft model of carcinogenesis. Treatment of either cell line with genistein before implantation into nude mice diminished the cells' tumorigenic potential. These data suggest that initiation of the differentiation program provides a protective effect against tumor growth in mice xenografts.
Anti-Estrogenic Actions of Genistein
Estrogenic and anti-estrogenic actions of genistein in human
Epidemiological and clinical studies suggest potential chemopreventive effects for the phytoestrogen genistein (GEN) against breast cancer. Proliferation of estrogen receptor positive MCF-7 breast cancer calls was determined after treatment with GEN (4, 5, 7-trihydroxyisoflavone). Thymidine incorporation assay, indicated that GEN significantly increased DNA synthesis at 10 micromolars compared to controls. In contrast, there was a 50% reduction in DNA synthesis at 25 micromolars, indicating an anti-estrogenic role for this drug. To elucidate the mechanism by which GEN exhibits the dose-dependent estrogenic or anti-estrogenic actions, its influence on enzymes of polyamine metabolism; ornithine decarboxylase (ODC), S-adenosylmethionine decarboxylase (SAMDC) and Spermidine/spermine-N-acetyltransterase (SSAT) was studied. Polyamines are cellular cations involved in cell proliferation and differentiation and their levels are regulated by estradiol in MCF-7 cells. GEN significantly increased ODC and SAMDC activity at 10 micromolars concentration. At growth inhibitory concentrations of GEN, however, these enzymes were inhibited. There was also a dose-dependent increase in SSAT levels with GEN treatment. These results indicate that a possible mechanism for GEN action might involve a polyamine pathway, eliciting growth promotive and suppressive effects depending on the concentration of the drug.
Genistein Inhibits Prostate Cancer
Inhibition of human prostate cancer cell proliferation by genistein.
Prostate cancer risk is low in countries with a high soy intake, and the soy phytoestrogen genistein inhibits prostate cancer cell proliferation. Our aims were to confirm prostate cancer cell growth inhibition and to explore possible mechanisms. We used androgen receptor (AR) and estrogen receptor positive LNCaP cells, AR- and ER- DU-145 cells, and AR- but possibly ER+ PC-3 cells. 24 hours after plating vehicle or genistein (12.5, 25, 37.5 ~g/ml) were added. At this time and after 24, 48 or 72 hours, the number of viable cells was counted by hemocytometer and dye exclusion. Cells were also harvested for flow cytometry, DNA laddering and TUNEL analysis. Genistein was no1 cytotoxic, but inhibited growth of PC-3 cells dose-relatedly, and abolished growth of LNCaP and DU-145 cells at all doses. Genistein induced apoptosis in LNCaP cells, but not in PC-3 and DU-145 cells (flow cytometry). The highest dose caused 20% of cells in apoptosis after 24 furs, but there was no apoptosis in the vehicle control. This was confirmed by DNA laddering and TUNEL analysis. Genistein caused a partial cell cycle arrest in PC-3 (shift to G0/G1) and DU-145 cells (shift to G2/M), but not in LNCaP cells. Thus, genistein inhibits human prostate cancer cell proliferation by various mechanisms, regardless of their AR/ER status.
Ribavirin and Hepatitis C
Ribavirin enhances the efficacy but not the adverse effects of interferon in chronic hepatitis C. Schalm S.W.; Hansen B.E.; Chemello L.; Bellobuono A.; Brouwer J.T.; Weiland O.; Cavalletto L.; Schvarcz R.; Ideo G.; Alberti A., Dr. S.W. Schalm,
Background/Aims: This study aimed to obtain a more precise estimation of the efficacy and tolerability of interferon-ribavirin combination therapy for chronic hepatitis C. Methods: A meta-analysis was carried out of individual patient data comprising about 90% of the published experience with combination therapy. The study was set in four European university-affiliated liver referral centers. A total of 186 individuals with chronic hepatitis C who had participated in three randomized controlled trials and one open study were selected for the study.
Fifty-one had received ribavirin monotherapy (1,000-1,200 mg/day), 37 received interferon monotherapy (3 MU 3x/week) and 78 interferon-ribavirin combination therapy (dosage as for monotherapy) for 6 months. Twenty patients served as controls. Follow-up after therapy was 6 months. Data analysis was by the multivariate logistical regression method. Results: The primary outcome measure for efficacy was the percentage with a sustained response (ALT normalization and HCV RNA negativity 6 months after therapy). The sustained response rate was significantly higher for interferon-ribavirin combination therapy than for interferon or ribavirin monotherapy (odds ratio IFN-Riba vs. IFN=9.8, 95% CI 1.9-50). The estimated probability of sustained response following interferon-ribavirin combination therapy was 51% for patients without previous IFN therapy, 52% for patients with previous IFN therapy and response-relapse, and 16% for previous IFN non-responders. No serious adverse events were observed and less than 10% withdrew. Conclusions: The efficacy of interferon-ribavirin therapy appears to be enhanced two- to threefold over interferon monotherapy in all major subgroups of chronic hepatitis C patients tested. In view of its acceptable toxicity profile, interferon-ribavirin combination therapy is a candidate for the new standard therapy for chronic hepatitis C.
Antiviral Therapy of Hepatitis C
Antiviral therapy of hepatitis C.
Background: Chronic hepatitis C can be treated with interferon therapy, but persistent viral clearance is achieved only in 20% of patients. Which patients have a high chance of viral clearance and what other treatmentmight enhance the effectivity of interferon therapy are reviewed.
Methods: Data from published randomized trials on interferon mono-therapy, ribavirin mono-therapy and combination therapy of interferon-ribavirin and interferon-ursodeoxycholic acid are analysed separately and in a meta-analysis of individual data.
Results: Interferon mono-therapy leads to viral clearance in only 10% of patients with genotype 1 and in less than 10% in cirrhosis; patients with plasma HCV RNA detectable at 4 weeks of therapy have only 2% chance of viral clearance.
Prolongation of therapy reduces relapse in treatment responders. Interferon-ribavirin combination therapy appears to enhance the efficacy 2-3 fold without increasing toxicity.
Conclusions: The benefit-risk/cost ratio of interferon mono-therapy can be improved by selection of patients, monitoring plasma HCV RNA at 4 weeks, and prolonging therapy to 12 months in responders with genotype 1. Interferon-ribavirin combination is promising for its enhanced efficacy.