Purpose: To determine the effects of genistein, a major soy isoflavone, on the expression of p21 in prostate cancer cell lines LNCaP and PC3, we investigated the effects of genistein on DNA methylation and histone modification.

Experimental Design: LNCaP and PC3 cell lines were treated with low dose (1-20µmol/L) of genistein for 72 hrs and the mRNA expression was determined by RT-PCR. Bisulfite modified PCR and DNA sequencing were employed to examine the DNA-methylation status. ChIP assay was performed to analyse chromatin modifications caused by genistein.

Results: Genistein (1-20µmol/L) induced p21 mRNA expression in LNCaP and PC3 cells in a dose dependent manner. DNA sequencing results revealed absence of p21 promoter methylation in both the cell lines. Genistein’s effect on p21 chromatin remodeling have not been reported so far. We found that genistein increased acetylated histones 3 and 4 at the unmethylated p21 promoter in addition to release of HDAC1 from LNCaP cells. Whereas the HDAC1 was absent in PC3 cells.

Conclusion: These results demonstrate that genistein can induce p21 expression by a mechanism that involves increase in the acetylated histones 3 and 4 without requiring promoter demethylation. It may contribute to the chemo preventive activity of this dietary isoflavone that functions possibly via a chromatin modification mechanism.

98th AACR Annual Meeting-- Apr 14-18, 2007; Los Angeles, CA