Cruciferous vegetables such as broccoli are known to contain high concentrations of sulforaphane, a compound that could form the basis of future anticancer treatments.
Researchers from the University of Pittsburgh Cancer Institute (UPCI) have announced that the extract is protective against oral cancer in mice and has been tolerated by a small group of healthy human volunteers.
These findings will be explored further later this year in a clinical trial involving human participants identified as being at high risk for head and neck cancer recurrence.
"People who are cured of head and neck cancer are still at very high risk for a second cancer in their mouth or throat, and, unfortunately, these second cancers are commonly fatal," says lead author Dr. Julie Bauman. "So we're developing a safe, natural molecule found in cruciferous vegetables to protect the oral lining where these cancers form."
Cruciferous vegetables, sometimes referred to as brassica vegetables, are characterized by strong aromas and a bitter flavor. Examples include broccoli, arugula, cabbage, cauliflower and collard greens.
According to the National Cancer Institute (NCI), cancer researchers are keen to study cruciferous vegetables because they contain a number of sulfur-containing chemicals known as glucosinolates - the substances responsible for the smell and taste of these vegetables.
When these glucosinolates are broken down, be it through food preparation or the process of eating, they form biologically active compounds. Researchers have previously found that some of these compounds can inhibit the development of cancer in some of the organs of mice and rats.
Sulforaphane significantly reduced oral cancer incidence and tumor numbers in mice
One such compound, sulforaphane, was the focus of the team's research. In collaboration with Dr. Daniel E. Johnson, a senior scientist from the UPCI Head and Neck Cancer Program, Dr. Bauman spent several months testing the effects of sulforaphane on mice predisposed to oral cancer.
Sulforaphane reduced both the incidence of oral cancer and the number of tumors that developed in the mice significantly. This finding led the researchers to test a mixture of fruit juice and broccoli sprout extract rich in sulforaphane on 10 healthy human volunteers.
No ill-effects occurred, and at the same time, the researchers detected certain protective changes in the lining of the volunteers' mouths, suggesting that the compound was absorbed and directed toward the tissue in this area.
To follow up these results, the researchers will now conduct a clinical trial involving 40 participants who have previously received treatment for head and neck cancers. For the trial, each participant will be given capsules containing broccoli seed powder.
"We call this 'green chemoprevention,' where simple seed preparations or plant extracts are used to prevent disease," explains Dr. Bauman. "Green chemoprevention requires less money and fewer resources than a traditional pharmaceutical study, and could be more easily disseminated in developing countries where head and neck cancer is a significant problem."
If the participants can tolerate this treatment and the capsules affect the oral lining enough to be preventive against cancer, further clinical trials could be conducted on a larger scale.
"The clear benefit of sulforaphane in preventing oral cancer in mice raises hope that this well-tolerated compound also may act to prevent oral cancer in humans who face chronic exposure to environmental pollutants and carcinogens," states Dr. Johnson.
The study was funded by a grant from the NCI, and the team's findings have been presented at the American Association for Cancer Research's Annual Meeting in Philadelphia.
For more information about the health benefits of broccoli, read Medical News Today's Knowledge Center article about the vegetable.