Broccoli could stop breast cancer from spreading. Sulforaphane, a component of the vegetable is the key, say scientists with the University of Michigan.
They took mice with breast cancer and injected varying concentrations of sulforaphane from the broccoli extract. There was a marked decrease in the cancer stem cell population after treatment with sulforaphane, with little effect on the normal cells.
Further cancer cells from mice treated with sulforaphane were unable to generate new tumours.
The researchers then tested sulforaphane on human breast cancer cell cultures in the lab, finding similar decreases in the cancer stem cells.
Study author Professor Duxin Sun from the University of Michigan, said: "Sulforaphane has been studied previously for its effects on cancer, but this study shows that its benefit is in inhibiting the breast cancer stem cells.
"This new insight suggests the potential of sulforaphane or broccoli extract to prevent or treat cancer by targeting the critical cancer stem cells."
Co-author Dr Max Wicha said: "This research suggests a potential new treatment that could be combined with other compounds to target breast cancer stem cells.
"Developing treatments that effectively target the cancer stem cell population is essential for improving outcomes."
The concentrations of sulforaphane used in the study were higher than what can be achieved by eating broccoli or broccoli sprouts.
Results of the study on mice and cell cultures appear in the May 1 issue of Clinical Cancer Research.
Prior research suggests the concentrations needed to impact cancer can be absorbed by the body from the broccoli extract, but side effects are not known. While the extract is available in capsule form as a supplement, concentrations are unregulated and will vary.
This work has not been tested in patients, and patients are not encouraged to add sulforaphane supplements to their diet at this time.
Researchers are currently developing a method to extract and preserve sulforaphane and will be developing a clinical trial to test sulforaphane as a prevention and treatment for breast cancer.