A bacterium responsible for the vast majority of stomach cancers, a leading cause of cancer death worldwide, and ulcers may have met its match, scientists from Johns Hopkins and the French National Scientific Research Center report in the May 28 issue of the Proceedings of the National Academy of Sciences.
The research team discovered that sulforaphane, a compound found in broccoli and broccoli sprouts, kills the bacterium in laboratory studies. The findings should lead quickly to clinical trials to see whether dietary intake of vegetables containing sulforaphane can relieve infection, the researchers say.
In all but 15 to 20 percent of cases, combinations of powerful antibiotics can kill helicobacter pylori, the bacterium that was recognized 20 years ago as the cause of debilitating stomach ulcers and often fatal stomach cancers. Unfortunately, the regions of the world where the infection is most common are the same places where using antibiotics is most economically and logistically difficult.
"In some parts of Central and South America, Africa and Asia, as much as 80 percent to 90 percent of the population is infected with helicobacter, likely linked to poverty and conditions of poor sanitation," says study leader Jed Fahey, a plant physiologist in the Department of Pharmacology and Molecular Sciences at the Johns Hopkins School of Medicine. "If future clinical studies show that a food can relieve or prevent diseases associated with this bacterium in people, it could have significant public health implications in the United States and around the world."
In their laboratory experiments, the scientists discovered that purified sulforaphane even killed helicobacter that was resistant to commonly used antibiotics. They also proved that sulforaphane can kill the bacterium whether it's inside or outside cells. In people, cells lining the stomach can act as reservoirs of helicobacter, making it more difficult to get rid of the infection, says Fahey.
Even though the pure compound kills helicobacter efficiently, it remains to be seen whether dietary sources of sulforaphane (broccoli or broccoli sprouts, for instance) have similar effects. If so, vegetables native or adapted to various regions could be used by local populations to reduce helicobacter infection, notes Fahey, who has compiled a list of vegetables that contain sulforaphane or related compounds.
"We've known for some time that sulforaphane had modest antibiotic activity," says Fahey, who is also affiliated with the Center for Human Nutrition at the Johns Hopkins Bloomberg School of Public Health. "However, its potency against helicobacter, even those strains resistant to conventional antibiotics, was a pleasant surprise."
Sulforaphane was initially isolated from broccoli at Johns Hopkins because of its ability to protect cells against cancer by boosting their production of "phase 2" enzymes, a family of proteins that detoxify certain cancer-causing agents and damaging free radicals. However, the compound's antibiotic abilities are not well understood and are likely to occur through some other mechanism, says Fahey.
Sulforaphane can protect against chemically induced stomach cancer in mice, the research team also found, but more studies are needed to know whether it can do the same against helicobacter-induced stomach cancer and whether dietary sulforaphane, rather than pure sulforaphane, will do the trick.
The French group was led by Alain Lozniewski. Other authors on the report are Xavier Haristoy and Isabelle Scholtus of the French National Scientific Research Center; Patrick Dolan and Thomas Kensler of the Johns Hopkins Bloomberg School of Public Health; and Katherine Stephenson and Paul Talalay of the Johns Hopkins School of Medicine.
The experiments were funded by the Lewis B. and Dorothy Cullman Foundation, the Barbara Lubin Goldsmith Foundation, the McMullan Family Fund and the U.S. National Institutes of Health.
Fahey, Talalay and The Johns Hopkins University own stock in Brassica Protection Products (BPP), a company whose mission is to develop chemoprotective food products and which sells broccoli sprouts. Fahey and Talalay are board members and scientific consultants to BPP, and stock they own is subject to certain restrictions under University policy. The terms of this arrangement are being managed by The Johns Hopkins University in accordance with its conflict of interest policies.