It's no secret that men and women who eat lots of vegetables seem more likely to avoid prostate or breast cancer, but researchers now think the chemical in broccoli could also be used to treat the cancers as well.

No one has tested the chemical on humans yet, however, and it may take years to turn it into a usable drug. "It's interesting early work, but it's a long way from something going on in a test tube to exactly what goes on in humans," says Dr. Durado Brooks, director of prostate and colorectal cancers for the American Cancer Society.

Prostate cancer is the most commonly diagnosed cancer among men in the United States and kills about 30,000 each year, according to the National Prostate Cancer Coalition. A number of treatments are available, but side effects commonly include incontinence and impotence.

Prostate cancer rates are lower in countries where people eat plenty of fruits and vegetables, although the exact link between diet and the disease isn't clear, Brooks says. Researchers at the University of California at Berkeley decided to investigate the cancer-fighting effects of chemicals in cruciferous vegetables such as broccoli, cauliflower, kale, Brussels sprouts and cabbage.

The researchers found that a chemical known as 3,3'-diindolylmethane (DIM), a byproduct of eating cruciferous vegetables, appeared to prevent the growth of breast cancer cells. They next turned to prostate cancer cells.

"We realized that what was missing was a comprehensive study of how these natural compounds affect the growth and function of reproductive cancer cells," says study co-author Gary Firestone, a professor of molecular and cell biology at the University of California at Berkeley.

The researchers found that prostate cancer cells treated with DIM grew 70 percent slower than untreated cells. Their research will appear in the June 6 issue of the Journal of Biological Chemistry.

The chemical appears to prevent cancer cells from receiving signals from the hormone testosterone, Firestone says. That, in turn, prevents the cells from growing.
By contrast, traditional hormone therapy for prostate cancer patients is designed to prevent testosterone from getting to the cells in the first place. "You cut off the signal that makes the prostate cancer cells grow," Firestone says.

It's possible that the chemical could be used in combination with hormone therapy, Firestone says, letting doctors dampen the side effects of lowering testosterone levels.
Producing drugs from the vegetables may be easy and inexpensive, he adds: "There's a lot of broccoli and cabbage, and you should be able to obtain a lot of this chemical at a very cheap price."

However, Brooks says hormone treatment is much less common than other prostate cancer treatments. Surgery and radiation are the usual treatments.

Research into chemicals derived from vegetables may be more important in terms of prevention, says Satya Narayan, an associate professor of anatomy and cell biology at the University of Florida. "These compounds may be of greater importance for prostate cancer prevention at the early stages of the prostate cancer development, instead of at the later stages when the cancer is advanced."

But it's still not clear how many vegetables men would need to eat to protect themselves from getting prostate cancer in the first place.

SOURCES: Durado Brooks, M.D., director, prostate and colorectal cancers, American Cancer Society, Atlanta; Gary Firestone, Ph.D., professor, molecular and cell biology, University of California at Berkeley; Satya Narayan, Ph.D., associate professor, anatomy and cell biology, University of Florida, Gainesville; June 6, 2003, Journal of Biological Chemistry .