| Recently the research of anticancer factors in food is more and more popular, among which genistein (not a nutrient in soy) is especially a global focus. The results of epidemiological investigations indicate that the incidence of breast cancer and prostatic carcinoma is relatively low in Asian, contrast to that for the inhabitants with the diet pattern of high animal food in western countries. The low incidence may be related to the high expenditure of genistein in soy. The results in subsequent researches confirm that genistein can inhibit the proliferation of many kinds of cancers and is related to the initiation, promotion and progression of cancers. The mechanism may include inhibitting vascularization and the activity of protein tyrosine kinase, inducing cell differentiation and apoptosis and so on. But the concrete molecular mechanism of genistein is not clear. Most scholars think the inhibition of genistein to the development of cancer cells is related to two pathways: cell apoptosis andcell cycle block. Based on these results, this study investigated the effect of genistein on MCF-7 cell proliferation, cell cycle, cell apoptosis and protein expression to provide a new idea.In order to study the mechanism of genistein on MCF-7 cells, MTT chromometry was used to study the effect of genistein to cell proliferation, flow cytometry was used to analyze cell cycle, acridine orange dye was applied to observe the morphological effect of genistein on cell apoptosis, DNA gel electrophoresis was made to survey the characteristic ladder band caused by apoptosis, Western Blot method was introduced to detect the protein expression of cyclin B1, cyclin E, cyclin D1, p21, Bc1-2, Bax, caspase 8 and caspase 3 respectively and two-dimensional gel electrophoresis was used to analyze the protein group expression.The results showed that the inhibitive effect became greater with the concentration increased or the effect time last. On the contrary, genistein slightly promoted cell proliferation when the concentration was below 5μmol/L, which was not statistically significant. With the increase of the genistein concentration, MCF-7 cell cycle distribution changed obviously, cells in the period of Go/G1 decreased and those in S and G2 increased, with an obvious dose-effect tendency. Genistein could promote the protein expression of cyclin B1 and p21 and show a dose-effect tendency too. But genistein didn't influence protein expression level of cyclin E. It could inhibit the protein expression level of cyclin D1, especially in thehigh concentration group, the protein expression of which was only 30.1 percent of that in control group.When the MCF-7 cells was treated with genistein at concentration of 25mol/L and above, characteristic cell apoptosis was observed, such as thickly-dyed chromatin and pyknosis. The characteristic ladder band was observed in DNA electropherogram when the concentration of genistein was about lOOumol/L. High concentration of genistein (>25umol/L) inhibited the protein expression of Bcl-2 with a dose-effect tendency. Likewise, genistein promoted the protein expression of Bax when the concentration was about lOumol/L. Obvious effect of genistein on the protein expression of caspase 8 and caspase 3 was not observed. After being treated by genistein at lOOumol/L for 4 days, the protein expression image of MCF-7 changed, in which 44 protein spots expression levels were up-regulated and 57 spots down-regulated.It can be concluded, that genistein can inhibit the cell proliferation of human breast cancer MCF-7 cells. The effect may be related to many paths; including G2/M cell cycle block, cell apoptosis and so on. The mechanism of cell cycle block may be related to the effect of genistein on the protein express of p21, cyclin Dl and the protein accumulation of cyclin Bl. Genistein can induce cell apoptosis of MCF-7 cells, which may be related to the effect of genistein on reducing the protein expression of Bcl-2, promoting Bax and decreasing the ratio of Bcl-2/Bax. |
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