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The effects of genistein on angiogenesis remain poorly understood. Some studies claim an antiangiogenic effect and others claim a pro-angiogenic one. Thus, the aim of this study was to determine if genistein may exhibit bivalent angiogenic effects. To address this question, genistein angiogenic modulatory effects were examined using an in vitro 3D angiogenesis model using human umbilical vein endothelial cells. In this model, a bivalent effect of genistein was demonstrated on sprouting angiogenesis, with angiogenic stimulation at low concentrations (0.001 – 1 µM) and inhibition at higher ones (25 – 100 µM). Enhancement of the endothelial tube formation correlated with an increase in human umbilical vein endothelial cell metabolic activity and proliferation. Inhibition of angiogenesis correlated with a decreased metabolic activity, proliferation, and migration. Moreover, high concentrations of genistein influenced human umbilical vein endothelial cell morphology. Expression of genes involved in the angiogenic process in response to genistein was measured to study the mechanism of action. Secretome profiling revealed that angiogenic regulators were modulated with genistein treatment. These results suggested a bivalent effect of genistein on human umbilical vein endothelial cell growth and angiogenesis, and further investigations on the benefit of genistein for cancer chemoprevention, cancer treatment, or pro-angiogenic therapies have to be carefully considered.

The higher incidence of thyroid carcinoma (TC) in women during reproductive years compared with men and the increased risk associated with the therapeutic use of estrogens have suggested a pathogenetic role exerted by these steroids in the development of TC. In the present study, we evaluated the potential of 17beta-estradiol (E2), genistein (G), and 4-hydroxyta-moxifen (OHT) to regulate the expression of diverse estrogen target genes and the proliferation of human WRO, FRO, and ARO thyroid carcinoma cells, which were used as a model system. We have ascertained that ARO cells are devoid of estrogen receptors (ERs), whereas both WRO and FRO cells express a single variant of ERalpha that was neither transactivated, modulated, nor translocated into the nucleus upon treatment with ligands. However, E2, G, and OHT were able either to induce the transcriptional activity of c-fos promoter constructs, including those lacking the estrogen-responsive elements, or to increase c-fos, cyclin A, and D1 expression. It is noteworthy that we have demonstrated that the G protein-coupled receptor 30 (GPR30) and the mitogen-activated protein kinase (MAPK) pathway mediate both the up-regulation of c-fos and the growth response to E2, G, and OHT in TC cells studied, because these stimulatory effects were prevented by silencing GPR30 and using the MEK inhibitor 2'-amino-3'-methoxyflavone (PD 98059). Our findings provide new insight into the molecular mechanisms through which estrogens may induce the progression of TC.

Phytoestrogens are a chemically diverse group of compounds made by plants that can have estrogenic effects in animals. Both tumorigenic and antitumorigenic effects have been reported. Although estrogens stimulate the growth of many breast tumors, there is a negative correlation between the incidence of breast cancer and the phytoestrogen-rich diet of certain Asian populations. To begin to resolve this paradox, we have analyzed the estrogenic properties of genistein and quercetin, two flavonoid phytoestrogens particularly abundant in soybeans. Trans-activation experiments with a transfected reporter gene for nuclear estrogen receptors (ER) show strong activation of the endogenous ER alpha by both phytoestrogens in two MCF7 human breast cancer cell lines. This is supported by the observation that the two phytoestrogens induce the down-regulation of ER alpha mRNA and protein levels. Using chimeric proteins consisting of the hormone binding domains of ER alpha and ER beta fused to the Gal4 DNA binding domain, we have established that genistein and quercetin are full estrogenic agonists of both ER isoforms. Ligand binding experiments with purified ER alpha and ER beta confirm that the two phytoestrogens are ER ligands. At concentrations that are sufficient to obtain substantial transcriptional activity, they stimulate the proliferation of two ER alpha-dependent breast cancer cell lines. At high concentrations, such as those reached with a soy-rich diet, genistein and quercetin are strong cytotoxic agents that even kill ER-independent HeLa cells. Thus, the mode of action of phytoestrogens and the balance between being risk or chemopreventive factors for breast cancer may depend on the dietary load.

The consumption of a plant-based diet can prevent the development and progression of chronic diseases associated with extensive neovascularization, including the progression and growth of solid malignant tumours. We have previously shown that the plant-derived isoflavonoid genistein is a potent inhibitor of cell proliferation and in vitro angiogenesis. Moreover, the concentration of genistein in the urine of subjects consuming a plant-based diet is 30-fold higher than that in subjects consuming a traditional Western diet. We have also reported that certain structurally related flavonoids are more potent inhibitors than genistein. Indeed, 3-hydroxyflavone, 3',4'-dihydroxyflavone, 2',3'-dihydroxyflavone, fisetin, apigenin and luteolin inhibit the proliferation of normal and tumour cells as well as in vitro angiogenesis at half-maximal concentrations in the lower micromolar range. The wide distribution of isoflavonoids and flavonoids in the plant kingdom, together with their anti-angiogenic and anti-mitotic properties, suggest that these phytoestrogens may contribute to the preventive effect of a plant-based diet on chronic diseases, including solid tumours. Baillieres Clin Endocrinol Metab

This study addresses the role of store-operated Ca2+ influx in the regulation of exocytosis in inflammatory cells. In HL-60 granulocytes, which do not possess voltage-operated Ca2+ channels, the chemotactic peptide fMet-Leu-Phe (fMLP) was able to stimulate store-operated Ca2+ influx and to trigger exocytosis of primary granules. An efficient triggering of exocytosis by fMLP required the presence of extracellular Ca2+ and was inhibited by blockers of store-operated Ca2+ influx. However, receptor-independent activation of store-operated Ca2+ influx through thapsigargin did not trigger exocytosis. fMLP was unable to stimulate exocytosis in the absence of cytosolic free Ca2+ concentration [Ca2+]c elevations. However, a second signal generated by fMLP synergized with store-operated Ca2+ influx to trigger exocytosis and led to a left shift of the exocytosis/[Ca2+]c relationship in ionomycin-stimulated cells. The synergistic fMLP-generated signaling cascade was long-lasting, involved a pertussis toxin-sensitive G protein and a phosphatidylinositol 3-kinase. In summary, store-operated Ca2+ influx is crucial for the efficient triggering of exocytosis in HL-60 granulocytes, but, as opposed to Ca2+ influx through voltage-operated Ca2+ channels in neurons, it is not a sufficient stimulus by itself and requires synergistic receptor-generated signals.