Goal now: Fine-tune it
Scientists at Johns Hopkins and Tsukuba University in Japan have confirmed the existence of a long-suspected natural system the body uses to block the cancer-causing effects of toxic chemicals in food and the environment.
The system hinges on a sharp boost in protective enzymes, called phase II enzymes, which can dispose of toxic chemicals. The enzymes effectively neutralize toxins' ability to damage DNA and trigger cancer, the researchers say.
In two studies appearing in the current Proceedings of the National Academy of Sciences, they've not only demonstrated the fundamental workings of the system, but have also pinpointed the key "switch" that regulates it. "We've gained long-awaited proof of a basic mechanism that can reduce the risk of cancer," says molecular pharmacologist and team member Paul Talalay, M.D.
Scientists already know that natural substances in plants, such as the sulforaphane in broccoli, as well as some man-made chemicals, can tap into this system that they're somehow "chemoprotective" but the route hasn't been clear. The new work, a result of 20 years' research, "confirms that raising the levels of phase II enzymes can offer a highly effective way to achieve protection against carcinogenesis," says Talalay. "We always had faith," he adds; "Now, in our animal studies, we have a direct demonstration."
"Our precise understanding of this system should make it fairly easy to design drugs that can fine-tune it," says researcher Thomas W. Kensler, Ph.D., a Hopkins toxicologist who's now overseeing early clinical trials of one such drug in China. "We have evidence that we can increase the system's levels of protection in people," he says, "and are planning long-term studies that would reveal any lowered incidence of cancer."
In the study, the researchers focused on strategies cells use to control activity of the phase II enzymes. "The levels of these enzymes are tight
Contact: Marjorie Centofanti
Johns Hopkins Medical Institutions