Effect of dietary supplementation of soybeans on experimental metastasis of melanoma cells in mice

Nutrition and melanoma prevention

Melanoma has continued to rise in incidence despite public efforts to promote sun protection behaviors. Because sunscreen use does not completely prevent skin cancer induced by ultraviolet radiation, additional chemopreventive methods for protecting against and reversing the effects of ultraviolet photodamage need evaluation. Recent years have brought increased interest in dietary factors, such as natural botanicals and vitamins, for the prevention of melanoma. This contribution provides a narrative review of the relevant, nutrition-related literature found by searching the keywords "melanoma chemoprevention," "nutrition and melanoma," "dietary botanicals and melanoma prevention," "green tea and melanoma," "vitamin D and melanoma," and "vitamin E and melanoma" in the PubMed database. Although randomized controlled trials of humans are lacking, basic science and epidemiologic studies show promising benefits of many natural products in chemoprevention for melanoma. Future studies, hopefully, will yield concrete answers and clarify the role of commonly available dietary nutrients in melanoma chemoprevention.

Effects of phyto-oestrogens on tissues

Recent investigations on the effects of phyto-oestrogens on various tissues have revealed that these diverse molecules may improve human health, particularly by protecting against certain chronic diseases. After a brief examination of the food sources, structures, and general cellular actions of the major phyto-oestrogens, current research findings on cardiovascular disease, skeletal tissues, and reproductive cancers are reviewed. Phyto-oestrogen concentrations in blood may be maintained at high levels in those consuming soyabean (Glycine max)-based food daily at several meals and exert their effects on target cells through either genomic effects via the classical oestrogen receptors or non-genomic effects mediated by membrane-bound oestrogen receptors or other cellular proteins. The expression of oestrogen receptor (OR) subtypes alpha (a) and beta (beta) varies across tissues, and cells that preferentially express OR-beta, which may include bone cells, are more likely to respond to phyto-oestrogens. Conversely, reproductive tissues contain relatively more OR-a and may, thus, be differently affected by phyto-oestrogens. Soyabean phyto-oestrogens appear to prevent the progression of atherosclerosis through multiple interactions, including lowering of plasma lipids and lipoproteins, increased vasodilatation and, possibly, decreased activation of blood platelets and vascular smooth muscle cells. However, a favourable impact on cardiovascular disease morbidity and mortality by a soyabean-enriched western-type diet remains to be shown, and unresolved questions remain regarding dose and form of the phyto-oestrogens in relation to risks and benefits. The isoflavones of soyabean have been shown consistently to have bone-retentive effects in animal studies by several investigators using rodent models, although intakes must be above a relatively high threshold level for a lengthy period of time, and little or no extra benefit is observed with intakes above this threshold level. The reports of modest or no effects on prevention of bone loss in human and non-human primate studies respectively, may be due to the limited doses tested so far. The relationship between soyabean-food intake and cancer risk has been more extensively investigated than for any other disease, but with less certainty about the benefits of long-term consumption of phyto-oestrogen-containing foods on prevention of cancer. The observations that breast and prostate cancer rates are lower in Asian countries, where soyabean foods are consumed at high levels, and the high isoflavone content of soyabeans have led to examination of the potential protective effects of phyto-oestrogens. Establishing diet-cancer relationships has proved difficult, in part because of the conflicting data from various studies of effects of soyabean-diets on cancer. Epidemiological evidence, though not impressive, does suggest that soyabean intake reduces breast cancer risk. The isoflavone genistein has a potent effect on breast cancer cells in vitro, and early exposure of animals to genistein has been effective in reducing later development of mammary cancer. Thus, continuous consumption of soyabean foods in early life and adulthood may help explain the low breast cancer mortality rates in Asian countries. Although the evidence for a protective effect against prostate cancer may be slightly more supportive, more research is needed before any firm conclusions can be made about the phyto-oestrogen-cancer linkages.

Preliminary studies on induction of apoptosis by genistein on HepG2 cell line

Consumption of soy products has been linked to lower the incidence of number of cancers. Genistein, one of the principal soy isoflavones, has been shown to inhibit the growth of a number of tumor cell lines in vitro. In this study, we investigate the effects of genistein on cell growth and apoptosis in human hepatocellular carcinoma HepG2 cell by looking for the formation of nuclear apoptotic bodies and DNA ladder formation. Additionally, flow cytometry analysis with propidium iodide staining has been conducted to detect the apoptotic cells. We found inhibition of cell growth and apoptotic nuclei, DNA fragmentation and increased apoptotic cells after treatment with genistein, indicating apoptotic cell deaths. From these results we observed that genistein inhibits the growth of HepG2 cells and induce apoptosis, however, further definitive studies are needed. These results may support the potentially effective chemopreventive and/or chemotherapeutic of genistein against liver cancer.

Dietary supplementation with high-selenium soy protein reduces pulmonary metastasis of melanoma cells in mice

The effect of high-selenium (Se) soy protein on pulmonary metastasis of murine B16BL6 melanoma cells was investigated in male C57BL6 mice. Isolated soy proteins (ISP) from soybeans grown with and without Se foliar application during seed development were compared. Five diets were studied, a basal AIN-93G diet or a basal diet containing 10% low-Se ISP, 5% low-Se + 5% high-Se ISP, 10% high-Se ISP, or 10% low-Se ISP supplemented with Se equivalent to that of the 10% high-Se ISP diet. The Se concentrations of the 5 diets were 0.13, 0.13, 1.9, 3.6, and 3.0 microg/g, respectively. Mice were fed the diet for 2 wk before and 2 wk after an i.v. injection of 5 x 10(4) viable cells. At necropsy, the number and size of tumors that had developed in the lungs were determined. In the control group, 13/18 mice exhibited > or = 50 tumors. The numbers of mice with > or = 50 tumors were 8/18, 7/18, 3/18, and 6/17 in the ISP-fed groups, respectively. The differences between the 10% high-Se ISP group, the Se-supplemented 10% low-Se group, and the control were significant (P < 0.05). Dietary supplementation with 10% low-Se ISP significantly decreased the mean number of tumors per group and the tumor size compared with the control. A greater reduction in these variables occurred in mice fed the 10% high-Se ISP diet. The inhibition by the Se-supplemented 10% low-Se ISP diet was similar to that by the 10% high-Se ISP diet. The whole-blood Se concentration was inversely related to the tumor number (R = -0.87, P = 0.052), tumor cross-sectional area (R = -0.91, P < 0.05), and tumor volume (R = -0.93, P < 0.05). These findings suggest that Se is responsible for the greater antimetastatic effect of the high-Se ISP. We conclude that the high-Se soy protein has a greater inhibitory effect than the low-Se soy protein on pulmonary metastasis of melanoma cells in mice.

Dietary supplementation with isolated soy protein reduces metastasis of mammary carcinoma cells in mice

The present study investigated the effect of dietary supplementation with isolated soy protein (ISP) on pulmonary metastasis of carcinoma cells from primary mammary tumors induced by orthotopic injection of 4526 murine mammary carcinoma cells in female BALB/c mice. Three diets were compared: a basal AIN-93G diet and the basal diet supplemented with 10% or 20% ISP. After three weeks on the experimental diets, each mouse was injected 4 x 10(5) carcinoma cells into the right inguinal mammary fat pad. The primary tumors were excised when they reached a size of 1.0 cm in diameter. After surgery, mice were maintained on their respective diets for another three weeks. At necropsy, the incidence of metastasis, the number and size of macroscopic tumors, and the number of microscopic tumors in the lungs were determined. The incidence of mice with macroscopically visible tumors was 93%, 76%, and 67%, and the median number of macroscopic tumor was 5, 2, and 1 for the control, 10%, and 20% ISP groups (P < or = 0.05, 20% ISP vs. control). The median cross-sectional area of the macroscopic tumors was 0.93 mm2, 0.80 mm2, and 0.31 mm2, and the median volume was 0.73 mm3, 0.56 mm3, and 0.14 mm3 for the control, 10%, and 20% ISP groups (P < or = 0.01, 20% ISP vs. control). Histological examination revealed fewer microscopically detectable tumors in the ISP groups compared with the control. These results demonstrated that dietary supplementation with ISP reduced pulmonary metastasis of carcinoma cells from primary mammary tumors in BALB/c mice.

Flavonoid effects relevant to cancer

Flavonoids, such as daidzein and genistein, present in dietary plants like soybean, have unique chemical properties with biological activity relevant to cancer. Many flavonoids and polyphenols, including resveratrol in red wine and epigallocatechin gallate in green tea, are known antioxidants. Some of these compounds have estrogenic (and antiestrogenic) activity and are commonly referred to as phytoestrogens. A yeast-based estrogen receptor (ER) reporter assay has been used to measure the ability of flavonoids to bind to ER and activate estrogen responsive genes. Recently, estrogenic compounds were also shown to trigger rapid, nongenomic effects. The molecular mechanisms, however, have not been completely detailed and little information exists regarding their relevance to cancer progression. As a preliminary step toward elucidating rapid phytoestrogen action on breast cancer cells, we investigated the effect of 17-beta estradiol (E2), genistein, daidzein and resveratrol on the activation status of signaling proteins that regulate cell survival and invasion, the cell properties underlying breast cancer progression. The effect of these estrogenic compounds on the activation, via phosphorylation, of Akt/protein kinase B (Akt) and focal adhesion kinase (FAK) were analyzed in ER-positive and -negative human breast cancer cell lines. E2, genistein and daidzein increased whereas resveratrol decreased both Akt and FAK phosphorylation in nonmetastatic ER-positive T47D cells. In metastatic ER-negative MDA-MB-231 cells, all estrogenic compounds tested increased Akt and FAK phosphorylation. The inhibitory action of resveratrol on cell survival and proliferation is ER dependent. Therefore, all estrogenic compounds tested, including resveratrol, may exert supplementary ER-independent nongenomic effects on cell survival and migration in breast cancer cells.

Effects of dietary, drinking, and smoking habits on the prognosis of gastric cancer

Although it has been clarified that dietary, drinking, and smoking habits contribute to the onset of gastric cancer, little is known about their impact on prognosis of gastric cancer. To examine this question, a prognostic analysis was conducted using data from Aichi Cancer Center Research Institute and Hospital. From January 1988 to December 1994, information on 877 gastric cancer patients (578 men and 299 women) regarding habitual smoking and drinking, food consumption, histological grade, and clinical stage of tumor as well as follow-up results were collected. Survival status of all patients was followed up until December 1998, and the survival function was estimated by the Kaplan-Meier method. Proportional hazard analysis was used to test the effect of each lifestyle item on gastric cancer death. After controlling for age, gender, histological grade, and stage of disease, hazard ratios (HR) were calculated. Values for consumption of raw vegetables [HR = 0.74, 95% confidence interval (CI) = 0.56-0.98], tofu (HR = 0.65, 95% CI = 0.42-0.99), and chicken meat (HR = 0.61, 95% CI = 0.39-0.95) more than three times per week demonstrated significantly decreased risk. However, the risk ratio was 2.53 (95% CI = 1.22-5.29) for habitual smokers, and an inverse dose-response relationship was also found between ever smoking and gastric cancer patient survival. Therefore, this study suggested that frequent intake of raw vegetables and tofu is favorable, whereas habitual smoking is an adverse prognostic factor for gastric cancer. Our study implies that an improvement of survival of Japanese gastric cancer might be achieved by lifestyle improvement.

Soy for breast cancer survivors: a critical review of the literature

A variety of health benefits, including protection against breast cancer, have been attributed to soy food consumption, primarily because of the soybean isoflavones (genistein, daidzein, glycitein). Isoflavones are considered to be possible selective estrogen receptor modulators but possess nonhormonal properties that also may contribute to their effects. Concern has arisen over a possible detrimental effect of soy in breast cancer patients because of the estrogen-like effects of isoflavones. Genistein exhibits a biphasic effect on the growth of MCF-7 cells in vitro, stimulating proliferation at low concentrations but inhibiting it at high concentrations. In ovariectomized athymic mice implanted with MCF-7 cells, both genistein and soy protein stimulate tumor growth in a dose-dependent manner. In contrast, in intact mice fed estrogen, genistein inhibits tumor growth. Although two studies in premenopausal women suggested that soy exerts estrogenic-like effects on breast tissue, recently conducted year-long studies indicated that isoflavone supplements do not affect breast tissue density in premenopausal women and may decrease density in postmenopausal women. These latter effects are opposite to those of hormone replacement therapy (HRT). Importantly, substantial data suggest that the progestogen, not the estrogen, component of HRT increases risk of developing breast cancer. Furthermore, recently conducted studies have failed to find that even HRT reduces survival in breast cancer patients. Overall, the data are not impressive that the adult consumption of soy affects the risk of developing breast cancer or that soy consumption affects the survival of breast cancer patients. Consequently, if breast cancer patients enjoy soy products, it seems reasonable for them to continue to use them.

Phytoestrogens and healthy aging: gaps in knowledge. A workshop report

There is an increasing public interest in foods and dietary supplements containing phytoestrogens for the maintenance of health. A workshop was convened to assess evidence for the potential benefits of phytoestrogen-containing foods or supplements on diseases or conditions affecting older populations. Preclinical, clinical, and epidemiologic data on the cardiovascular system, various cancers, bone diseases, and menopausal symptoms were the focus of the discussions. Research on the basis of consumer food choices as well as a presentation from the FDA regarding approval of the use of soy foods to reduce the risk of cardiovascular disease were also presented. Based on the information presented, isoflavone-containing soy foods may have favorable effects on the cardiovascular system, but major knowledge gaps still exist regarding effects ofphytoestrogen supplements on bone diseases, various cancers, menopausal symptoms, and cognitive function.

Dietary supplementation with secoisolariciresinol diglycoside (SDG) reduces experimental metastasis of melanoma cells in mice

We investigated the effect of dietary supplementation with secoisolariciresinol diglycoside (SDG), a lignan precursor isolated from flaxseed, on experimental metastasis of B16BL6 murine melanoma cells in C57BL/6 mice. Four diets were compared: a basal diet (control group) and the basal diet supplemented with SDG at 73, 147 or 293 micromol/kg (equivalent to SDG provided in the 2.5, 5 or 10% flaxseed diet). Mice were fed the diet for 2 weeks before and after an intravenous injection of 0.6 x 10(5) tumor cells. At necropsy, the number and size of tumors that formed in the lungs were determined. The median number of tumors in the control group was 62, and those in the SDG-supplemented groups were 38, 36 and 29, respectively. The last was significantly different from the control (P < 0.01). Dietary supplementation with SDG at 73, 147 and 293 micromol/kg also decreased tumor size (tumor cross-sectional area and volume) in a dose-dependent manner compared with the control values. These results show that SDG reduced pulmonary metastasis of melanoma cells and inhibited the growth of metastatic tumors that formed in the lungs. It is concluded that dietary supplementation with SDG reduces experimental metastasis of melanoma cells in mice.

Soybean isoflavones reduce experimental metastasis in mice

We investigated the effect of dietary supplementation with isoflavones on pulmonary metastasis of B16BL6 murine melanoma cells in C57BL/6 mice. Mice were fed a basal AIN-93G diet or the basal diet supplemented with the isoflavones genistein and daidzein at 113 micromol/kg, 225 micromol/kg, 450 micromol/kg, or 900 micromol/kg for 2 wk before and after the intravenous injection of 0.5 x 10(5) melanoma cells. At necropsy, the number and size of tumors that formed in the lungs were determined. The number of mice that had >15 lung tumors was 17 in the control group, and 16, 15, 13, and 10 in the groups fed isoflavones at 113 micromol/kg, 225 micromol/kg, 450 micromol/kg and 900 micromol/kg, respectively. The latter two were significantly different from the control (P Collapse

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MESH Headings

• Animals
• Body Weight
• Dietary Supplements
• Eating
• Genistein/urine
• Isoflavones/administration & dosage
• Isoflavones/therapeutic use
• Isoflavones/urine
• Lung Neoplasms/drug therapy
• Lung Neoplasms/pathology
• Lung Neoplasms/secondary
• Male
• Melanoma, Experimental/pathology
• Mice
• Mice, Inbred C57BL
• Neoplasm Transplantation
• Glycine max/chemistry

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Affiliation(s)

D Li Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA
J A Yee
M H McGuire
P A Murphy
L Yan

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Experimental studies on lignans and cancer

Mammalian lignans are produced from plant precursors such as secoisolariciresinol diglycoside (SDG) and matairesinol via the action of bacteria in the human or animal colon. While precursors are found in many plant foods, flaxseed is the richest source of SDG and was therefore used as a model to determine the anti-cancer effects of lignans. This paper reviews the experimental studies in animals and humans demonstrating the anti-cancer effects of flaxseed and its SDG as well as other studies relevant to the clinical use of lignans, such as those on their food sources, bio-availability and safety.

Dietary flaxseed supplementation and experimental metastasis of melanoma cells in mice

The present study investigated the effect of dietary supplementation of flaxseed, the richest source of lignans, on experimental metastasis of B16BL6 murine melanoma cells in C57BL/6 mice. Mice were fed a basal diet or the basal diet supplemented with 2.5, 5 or 10% flaxseed for 2 weeks before and after the intravenous injection of 0.75 x 10(5) melanoma cells. At necropsy, the number of tumors that developed in the lungs was counted, the cross-sectional area of tumors was measured and the volumes of tumors were calculated. The median number of tumors in mice fed the 2.5, 5 and 10% flaxseed-supplemented diets was 32, 54 and 63% lower than that of the controls, respectively. The addition of flaxseed to the diet also caused a dose-dependent decrease in the tumor cross-sectional area and the tumor volume. These results provide the first experimental evidence that flaxseed reduces metastasis and inhibits the growth of the metastatic secondary tumors in animals. It is concluded that flaxseed may be a useful nutritional adjuvant to prevent metastasis in cancer patients.