Synthetic dimer of indole-3-carbinol: second generation diet derived anti-cancer agent in hormone sensitive prostate cancer.

BACKGROUND Cruciferous vegetables have been found to have anti-prostate cancer effects. The active compounds mediating these effects include indoles such as indole-3-carbinol (I3C) and isothiocyanates. I3C is unstable having tissue tropic effects and clinical utility has been partly addressed by the synthesis of a more stable dimer diindolylmethane (DIM). METHODS Anti-proliferative activity was measured by XTT assay and cytosolic proteins quantitated by Western blot analysis. RESULTS DIM (IC50 50 µM) is a better anti-proliferative agent than I3C (IC50 150 µM) in androgen dependent LNCaP cells, inhibits DNA synthesis, and growth of R1881 stimulated LNCaP cells. Androgen receptor (AR), cyclin D1, and cdk4, induced by R1881, are downregulated by DIM. DIM downregulates phosphorylated Akt and phosphatidyl inositol 3-kinase and downstream inhibition of cyclin D1 and cdk4. CONCLUSION These studies provide evidence that DIM is a second-generation chemopreventive agent with a viable cellular target and has clinical potential as an anti-prostate cancer chemopreventive. © 2005 Wiley-Liss, Inc.