A compound found in broccoli and other cruciferous vegetables has been found to slow the growth of breast cancer cells, especially at early stages.

While sulforaphane has long shown evidence of value in cancer prevention, researchers at Oregon State University (OSU) and the Oregon Health & Science University suggested in a new study that it may play a role in slowing cancer growth as well.

The findings were the result of the first clinical studies to look at the effect of sulforaphane on breast tissues of women diagnosed with breast cancer.

Emily Ho, a professor at the OSU College of Public Health and Human Sciences, said "our original goal was to determine if sulforaphane supplements would be well tolerated and might alter some of the epigenetic mechanisms involved in cancer."

In a double-blind, randomized, placebo-controlled trial, 54 women with abnormal mammograms were given either a placebo or supplements that provided sulforaphane. The amount of sulforaphane they received would equate to about one cup of broccoli sprouts per day, if eaten as a food.

"We were surprised to see a decrease in markers of cell growth, which means these compounds may help slow cancer cell growth," said Ho. "This is very encouraging. Dietary approaches have traditionally been thought to be limited to cancer prevention, but this demonstrated it could help slow the growth of existing tumors."

Previous studies have found that women with a high intake of cruciferous vegetables, such as broccoli, cauliflower, cabbage or kale, have a decreased risk of breast cancer. In particular, sulforaphane appears to inhibit histone deacetylases, or HDACs, which in turn enhances the expression of tumor suppressor genes that are often silenced in cancer cells.

In the new study published in the journal Cancer Prevention Research, the intake of sulforaphane did reduce HDAC activity, as well as cancer cell growth.

As co-author of the study, Ho said it is possible that sulforaphane may be added to traditional approaches to cancer therapy, whether to prevent cancer, slow its progression, treat it or stop its recurrence.

Researchers said additional studies are needed to evaluate dose responses, work with larger populations, and examine the responses of other relevant molecular targets to either foods or supplements containing sulforaphane.