While the health benefits of broccoli have been investigated by researchers for some time, a study in the May 2010 issue of Clinical Cancer Research finds that a compound in broccoli called sulforaphane may also prevent the growth of cancer stem cells (CSCs). The findings are particularly relevant since many researchers believe that fighting cancer at the level of the stem cells represents the most promising form of treatment.

...“[s]ulforaphane from broccoli extracts is efficiently and rapidly absorbed in the human small intestine and distributed throughout the body,”...

Yanyan Li and colleagues studied mice who had been induced to develop breast cancer, and administered either sulforaphane or saline solution to the mice for two weeks. At the end of this period the tumors of the mice were analyzed for the growth of breast cancer cells and CSCs. The team found that CSCs were “eliminated” in mice who had received sulforaphane. What’s more, the growth of new tumors was completely suppressed in mice who were injected with sulforaphane-treated cells (that is, these cancer cells were unable to replicate themselves).

The researchers also administered sulforaphane to cultured human breast cancer cells (in vitro) and found similar results. The number and size of breast cancer cells, as well as the growth of CSCs, were significantly reduced in these cancer cells. The last part of the study actually uncovered the mechanism by which sulforaphane works – the researchers say that it is the “downregulation of Wnt/β-catenin self-renewal pathway by sulforaphane” that is behind ability of sulforaphane to inhibit CSC growth.

The results are exciting and may ultimately lead to future directions in cancer treatment and/or prevention. The authors write that “[s]ulforaphane from broccoli extracts is efficiently and rapidly absorbed in the human small intestine and distributed throughout the body,” although the doses used in the study were more than people could probably consume in their diets alone.

The authors sum it up by saying that “[t]hese studies support the use of sulforaphane for breast cancer chemoprevention. These findings provide a strong rationale for preclinical and clinical evaluation of sulforaphane or broccoli/broccoli sprouts for breast cancer therapies.” Future studies will need to look at whether similar results might be found in humans, and if so, what the appropriate – and safe – dosages and treatment length might be.