Well, this is one of the proposed mechanisms at least:
Broccoli compound targets key enzyme in late-stage cancer
Indole-3-carbinol, or I3C, is a chemical compound found in broccoli and other cruciferous vegetables and which is known to stop the growth of breast cancer cells. UC Berkeley researchers' discovery of how I3C works will help them modify the compound to improve its anti-cancer effects. (Firestone & Bjeldanes labs/UC Berkeley)
(PhysOrg.com) -- An anti-cancer compound found in broccoli and cabbage works by lowering the activity of an enzyme associated with rapidly advancing breast cancer, according to a University of California, Berkeley, study appearing this week in the online early edition of the journal Proceedings of the National Academy of Sciences.
The compound, indole-3-carbinol, is already undergoing clinical trials in humans because it was found to stop the growth of breast and prostate cancer cells in mice.
The new findings are the first to explain how indole-3-carbinol (I3C) stops cell growth, and thus provides the basis for designing improved versions of the chemical that would be more effective as a drug and could work against a broader range of breast as well as prostate tumors.