3,3'-diindolylmethane and genistein alter the effects of estrogen on prostate cancer cells
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Evidence suggests that 17beta-estradiol (E2) contributes to the risk of prostate cancer (PCa), whereas the phytochemicals genistein from soy and 3, 3'-diindolylmethane (DIM), derived from indole-3-carbinol (13C) in cruciferous vegetables, decrease the risk of prostate cancer (PCa). This study examined the potential of these phytochemicals to reduce the adverse effects of E2 on PCa. In LNCaP PCa cells (E2 sensitive) DIM decreased E2-induced proliferation. Genistein increased proliferation at low concentrations and decreased proliferation at higher concentrations; DIM abolished the increased proliferation by genistein. The E2 stimulation in LNCaP cells was consistent with dependence on the androgen receptor (AR) as was evidenced by inhibition of E2-induced proliferation with the anti-androgen casodex (CSDX), E2 stimulation of an androgen response element (ARE) luciferase reporter, and E2 stimulation of prostate specific antigen (PSA) protein expression. Both genistein and DIM abrogated the E2 stimulation of PSA. Genistein and DIM altered major E2 metabolism pathways in LNCaP and PC-3 (E2 insensitive) PCa cells by increasing expression of the 2-hydroxylation enzyme cytochrome P450 1A1 (CYP1A1) and the O-methylating enzyme catechol-o-methyltransferase (COMT) as determined by real time RT-PCR. The increase in COMT mRNA only occurred when the combination of DIM and genistein (151mumol/L) was used. Quantitation by mass spectrometry indicated an increase in 2-hydroxyestradiol (2-OHE2) and a decrease in 16alpha-hydroxyestrone (16alpha-OHE1), a result that should result in less estrogenicity and increased amounts of the anti-cancer metabolite 2-methoxyestrone. Furthermore, apoptosis studies in LNCaP and PC-3 cells that were treated with or without E2 in the presence of DIM and/or genistein revealed that estrogen significantly enhances DIM and genistein induced apoptosis. The enhancement of apoptosis by estrogen also occurred in MCF-7 breast cancer cells and C3 3A cervical cancer cells. Our conclusions are that DIM and genistein decrease effects of E2 that have the potential to promote PCa.