Antiproliferation effect and mechanism of prostate cancer cell lines as affected by isoflavones from soybean cake.

The objectives of this study were to determine the antiproliferation effect of prostate cancer cell lines LNCaP and PC-3 as affected by 4 isoflavone fractions prepared from soybean cake and isoflavone standards genistein and daidzein. With the MTT test, most treatments were effective in inhibiting prostate cancer cell growth at a low dose of 5 and 10 mug/mL. In cell cycle analysis, the fractions of aglycon, a mixture of acetylglucoside and aglycon, as well as genistein and a combination of genistein and daidzein standards exhibited a high G2/M ratio for LNCaP, as did the acetylglucoside, genistein and a combination of genistein and daidzein standards for PC-3. Results of Western blotting revealed an increase in p53 protein expression of LNCaP following treatments of the aglycon fraction, genistein and a combination of genistein and daidzein standards. However, all the treatments did not affect Bcl-2 protein expression significantly in both LNCaP and PC-3 cells. A decline in cyclin B1 expression of LNCaP was observed for all the treatments, with the mixture of acetylglucoside and aglycon possessing the most pronounced effect. But for PC-3, a decrease in cyclin B1 expression was shown for all the isoflavones, with the exception of malonylglucoside, glucoside and acetylglucoside fractions. The outcome of this study may provide a basis for possible production of functional food in the future with soybean cake as raw material.