Physiological concentrations of genistein and 17ß-estradiol inhibit MDA-MB-231 breast cancer cell growth by increasing BAX/BCL-2 and reducing pERK1/2.

AIM: The aim of the present study was to identify the mechanism by which genistein and 17ß-estradiol inhibit proliferation of MDA-MB-231 breast cancer cells. MATERIALS AND METHODS: The expression of cell signaling proteins involved in cell apoptosis, proliferation, and survival (BCL-2 associated X protein, BAX; B-cell lymphoma 2, BCL-2; extracellular signal regulated kinase, pERK1/2; and protein kinase B, pAKT) were examined by western blotting, and tested whether these effects correlated with cell proliferation and apoptosis. RESULTS: Compared to the control, 1 µM genistein plus 1 nM 17ß-estradiol significantly increased apoptosis, and the BAX/BCL-2 ratio, with a concomitant decrease in ERK1/2 phosphorylation. High concentrations of genistein (100 µM) both in the presence and absence of 17ß-estradiol also increased apoptosis; however, these changes were not correlated with the BAX/BCL-2 ratio or with phosphorylation of ERK1/2. CONCLUSION: These results suggest that different concentrations of genistein elicit cell responses through different signaling mechanisms. These results are especially relevant in premenopausal women with breast cancer who are on a soy diet.

Effect of genistein on p90RSK phosphorylation and cell proliferation in T47D breast cancer cells.

BACKGROUND: The molecular mechanisms of genistein's proliferative effects on breast cancer cells are largely unknown. This study aimed to examine estrogen-receptor (ER)-related signaling molecules involved in genistein-associated cell proliferation and survival (ERK1/2, p90RSK, JNK, Akt and NFκB) and to correlate these results to cell proliferation. MATERIALS AND METHODS: The effect of genistein on cell-signaling molecules was determined in T47D breast cancer cells by a Bioplex phosphoprotein detection kit. These results were confirmed by Western blotting and were correlated to cell proliferation by MTT assay. RESULTS: Low and high concentrations of genistein induced an ERK1/2-independent decrease in phosphorylated p90RSK. This effect was accompanied by decreased cell proliferation at high concentrations and an increased response at low concentrations of genistein following a 48-hour exposure. CONCLUSION: Concentration-dependent actions of genistein in T47D cells may be due to differential activation of signaling molecules.

Genistein in the presence of 17beta-estradiol inhibits proliferation of ERbeta breast cancer cells.

BACKGROUND/AIM: Genistein, a soy component, has been shown to have a biphasic proliferative effect in breast cancer cells, inhibiting in vitro cell proliferation at high concentrations (>10 micromol/l), while stimulating cell proliferation at lower concentrations (<10 micromol/l). However, epidemiological studies have shown an inverse correlation between the intake of genistein and the incidence of breast cancer. One of the possible reasons for this discrepancy could be the differing status of the estrogen receptor (ERalpha and/or ERbeta). Genistein selectively binds to ERbeta with strong affinity and thereby could be a potential chemotherapeutic agent against breast cancer of the ERalpha-negative and ERbeta-positive type. Therefore, the objective of the present study was to determine whether the proliferative effects of genistein were caused by its activity as a selective ERbeta agonist or merely as an antiestrogen. METHOD: This study was carried out in MDA-MB-231 (ERbeta) and T47D (ERalpha and ERbeta) human breast cancer cells. Cell proliferation was determined by the MTT (3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide) assay. The cells were grown in estrogen-starved media and exposed to genistein at different concentrations for 72 h, either in the presence or absence of 17beta-estradiol. RESULTS: A significant decrease in cell proliferation was seen in MDA-MB-231 cells at low concentrations of genistein in the presence of 17beta-estradiol, as compared to genistein alone. In T47D cells, which are known to have a predominance of ERalpha over ERbeta, genistein showed a biphasic cell proliferative response both in the presence and absence of 17beta-estradiol. CONCLUSIONS: Our results suggest that in cells with a predominance of ERalpha, genistein acts as an agonist to ERalpha, and in cells with ERbeta alone, genistein most likely acts as an antiestrogen. Our results also suggest that genistein could be useful as a chemotherapeutic agent in premenopausal women with breast cancer of the ERalpha-negative and ERbeta-positive type.

Effect of antiestrogens on EGF-mediated movement of human breast cancer cells.

In a previous study we compared the influence of several growth factors on breast cancer cells in culture and observed that epidermal growth factor (EGF) enhanced the invasiveness of estrogen receptor-positive breast cancer cells. The objective of the present study was to determine the influence of three unique antiestrogens on EGF-mediated movement of human breast cancer cells. The rate of movement of MCF-7 breast cancer cells was measured using time-lapse videomicroscopy (TLVM). The MCF-7 cells were pretreated with antiestrogen (either tamoxifen, ICI-182-780 (ICI) or 1,1-dichloro-cis-2,3-diarylcyclopropane (AII)) at 10(-6) mol/l for 4 days, and then treated with EGF (10(-10) mol/l) immediately prior to TLVM. EGF enhanced the motility of the MCF-7 cells at 30-90 min post-administration. However, EGF-mediated motility of the MCF-7 cells was inhibited by antiestrogen pretreatment, with TAM and ICI producing complete inhibition of EGF-induced motility. In conclusion, this study demonstrates that EGF enhances the rate of movement of MCF-7 breast cancer cells and that antiestrogen pretreatment inhibits EGF-mediated motility.

VEGF and VEGF receptor levels in retinal and brain-derived endothelial cells.

Vascular endothelial cell growth factor (VEGF) is an endothelial cell-specific angiogenic and permeability-inducing factor that has been implicated in the pathogenesis of diabetic retinopathy. The objectives of this study are to compare VEGF and VEGF receptor expression between retinal and brain-derived endothelial cells cultured in 5 or 30 mM glucose for 5 days. Our results show that expression of cell-surface VEGF receptors, assessed by flow cytometry, is higher in retinal-derived endothelial cells. RT-PCR results show that both retinal and brain-derived endothelial cells express comparable levels and types of VEGF. Exposure to 30 mM glucose for 5 days did not alter levels of VEGF or VEGF receptors. The higher level of VEGF receptor expression in retinal endothelial cells suggests that the retinal microcirculation may be more sensitive to the effects of VEGF and this may contribute to the pathogenesis of diabetic retinopathy.

The effect of antiestrogens on TGF-beta-mediated chemotaxis of human breast cancer cells.

BACKGROUND: In a previous study we compared the influence of several growth factors on cancer cells in culture and observed that transforming growth factor-beta (TGF-beta) enhanced the invasiveness of several breast cancer cell lines. The objective of the present study was to determine the influence of three unique antiestrogens on TGF-beta-mediated chemotaxis of human breast cancer cells. MATERIALS AND METHODS: The chemotactic activity of TGF-beta was assayed in vitro using collagen IV-coated transwell chambers with either MCF-7 or MDA-MB-231 human breast cancer cells. The cells were pretreated with antiestrogen for 4 days, harvested and placed in the upper transwell chamber. TGF-beta was added to the lower chamber and cell migration and collagenase release were determined following a 6-hour incubation. RESULTS: In this study TGF-beta enhanced the chemotaxis of both cell types with a much greater effect on the MDA-MB-231 cells. However, TGF-beta-mediated chemotaxis of the MCF-7 cells was inhibited by antiestrogen pretreatment while TGF-beta-mediated chemotaxis of the MDA-MB-231 cells was not altered. Further, neither TGF-beta nor antiestrogen treatment altered collagenase release from either cell line. CONCLUSION: The data demonstrate that pure antiestrogens are capable of inhibiting TGF-beta-mediated chemotaxis in estrogen receptor (ER)-positive breast cancer cells by a mechanism which is independent of collagenase release. Finally, the results of this study suggest a coupling of the TGF-beta and ER signaling pathways and indicate that TGF-beta may be an important therapeutic target for the treatment or inhibition of breast cancer metastasis.