Sulforaphane, found in cruciferous vegetables such as broccoli, activates a protective genetic pathway that detoxifies carcinogens in the body, protecting from oral cancer, researchers say.
The study, published in the journal Cancer Prevention Research, was led by Dr. Julie Bauman, co-director of the University of Pittsburgh Medical Center (UPMC) Cancer Center in Pennsylvania.
According to the Centers for Disease Control and Prevention (CDC), each year in the United States, over 30,000 new cases of oral cancer are diagnosed, and there are over 8,000 deaths due to oral cancer.
The survival rate for such cancers is quite low, with a 5-year survival rate of about 50 percent.
"With head and neck cancer, we often clear patients of cancer only to see it come back with deadly consequences a few years later," says Dr. Bauman.
Methods of treating oral cancers include surgery, radiation, and chemotherapy, but they can be disfiguring and costly.
Repeated exposure to carcinogens is the greatest risk factor for head and neck cancer. Cruciferous vegetables have a high concentration of sulforaphane; previous research has shown it can protect people against environmental carcinogens.
Dr. Bauman notes that previous attempts to develop drugs to reduce the risk of head and neck cancer recurrence "have been inefficient, intolerable in patients and expensive. That led us to 'green chemoprevention' - the cost-effective development of treatments based upon whole plants or their extracts."
Lab, mice, and human studies have been successful
To further investigate, Dr. Bauman and colleagues first treated human head and neck cancer cells with different doses of sulforaphane, as well as a control. They then compared them with healthy throat and mouth cells.
Results showed that the sulforaphane encouraged both cell types to increase levels of a protein that turns on specific genes that induce carcinogen detoxification, protecting cells from cancer.
Next, in a small preclinical trial, for several days, 10 healthy volunteers drank or swished juice mixed with broccoli sprout extract.
Not only did the study subjects have no significant problems tolerating the extract, but the lining of their mouths also showed that the same protective genetic pathway was activated in their mouths.
The researchers say this means the sulforaphane was absorbed and focused on at-risk tissue.
In a further experiment, the researchers used mice to see how the extract worked in those predisposed to head and neck cancer. Results showed that the mice that received the extract developed fewer tumors, compared with those that did not.
In light of the successful studies, Dr. Bauman and her colleagues have initiated a larger clinical trial in humans who have previously been cured of head and neck cancer. The participants are currently taking capsules with broccoli seed powder.
The researchers write:
"Together, our findings demonstrate preclinical chemopreventive activity of sulforaphane against carcinogen-induced oral cancer, and support further mechanistic and clinical investigation of sulforaphane as a chemopreventive agent against tobacco-related HNSCC [head and neck squamous cell carcinoma]."