The cancer-fighting properties of broccoli, a member of the crucifer family of vegetables, are not new and previous studies have related these benefits to the high levels of active plant chemicals called glucosinolates. These are metabolised by the body into isothiocynates, and evidence suggests these are powerful anti-carcinogens. The main isothiocynate from broccoli is sulforaphane.
Other studies have proposed that the compound indole-3-carbinol (I3C), a phytochemical found naturally in cruciferous vegetables, could also have potential prevention activity against hormone-responsive tumours, such as breast, ovarian and prostate cancer.
New data, published on-line ahead of print in the journal Carcinogenesis (doi:10.1093/carcin/bgl171) and presented recently at the National Cancer Research Institute Conference, adds to these studies by reporting that I3C could alter receptors in breast cancer cells and induced apoptosis (programmed cell death).
The researchers also reported that the green vegetable compound may also make the tumour cells more susceptible to pharmaceutical approaches.
"It is notoriously hard to conduct large-scale studies looking at the cancer preventing effects of these substances in our food, but the in vitro evidence is growing that these agents would make an ideal addition to preventive and combinatorial anti-cancer strategies," said lead researcher Professor Margaret Manson from the University of Leicester.
The scientists, funded by the Medical Research Council (MRC) looked at the impact of I3C on four different types of breast cancer cells (MDA-MB-468, MDA-MB-231, MCF7 and HBL100), and found that I3C-induced apoptosis in three of these cell types; MCF7, MDA-MB-468 and MDA-MB-231.
"Although we need to carry out further studies on tumours removed from patients, the potential benefits are clear," said Professor Manson.
"Dietary agents are kind to normal cells at doses, which can slow down or kill cancer cells. Combining them with drugs may enhance the drugs' effectiveness and could allow reduced doses to be given to patients.
"As dietary substances like I3C have a proven track record of being safe for the patient, we hope that the journey to clinical trials will be relatively straightforward," she said.
It was also suggested that the 'dose' of I3C present in cruciferous vegetables may not be sufficient to be high enough to replicate the effects seen in vitro which may open up opportunities for high-dose I3C extracts from vegetables or breeding of "super" forms of the veggies with higher amounts of I3C, along similar lines to the broccoli developed by British researchers said to contain three times the levels of sulforaphane than normal mature broccoli.
Some broccoli-extracts are currently available on the market, such as Cyvex's Nutrition's BroccoPlus, combines six per cent glucosinolates with sulforaphane, delivering high doses of these compounds in powder form, and B&D Nutritional Ingredients' sgs-100, a broccoli seed extract from a plant strain that is reported to be unusually high in sulforaphane glucisinolate (SGS).
Dr. Sheila Bingham, director of the MRC Centre for Nutrition and Cancer at the University of Cambridge said: "This study supports the growing evidence that food can be important in altering our susceptibility to cancer and possibly survival from it, and may help explain why fruits and vegetables are so important."
Josephine Querido, science information officer at Cancer Research UK, said: "This study adds to the evidence that I3C molecule - found in broccoli, cabbage and other cruciferous vegetables - can help block the growth of breast cancer cells."
But Querido stressed that the work was done in a laboratory, and that it was too soon to tell if I3C could have a role to play in breast cancer prevention and/or treatment.
"After stopping smoking, a healthy balanced diet including plenty of fruit and vegetables is the best way to reduce your risk of developing certain cancers," she said.