Soybean-Based Chemical May Help Prevent Oral Cancer

The findings are believed to be among the first in humans to indicate that the soybean derivative could prevent oral cancer, which has one of the lowest survival rates of all cancers. The study appears in the December issue of Clinical Cancer Research.

Dr. Frank Meyskens, director of the Chao Family Comprehensive Cancer Center, and Dr. William Armstrong, assistant professor of head and neck surgery at UCI, led a team that found that a chemical called Bowman-Birk Inhibitor reduced the size of precancerous lesions in the mouth--called oral leukoplakia--in about one-third of participants in the clinical trial.

"This study shows that it may be possible to stave off the development of leukoplakia and therefore prevent more cases of oral cancer from occurring," said Meyskens. "The best way to cure cancer is to prevent cancer, and we are encouraged by the fact that a simple dose of a chemical was able to achieve this without side effects. We hope that our continued clinical studies will give us more insight into how well Bowman-Birk Inhibitor can prevent this disease."

In the study, 32 participants took one lozenge of Bowman-Birk Inhibitor each day for a month. Ten participants showed a reduction in leukoplakia size by about half; over the entire group, the average decrease in size was about 24 percent.

Bowman-Birk Inhibitor was identified by chemists nearly 40 years ago. Although it is based on a chemical found in soybeans that prevents an enzyme called chymotrypsin from breaking down proteins in the body, its exact function is not known. Previous research has shown that Bowman-Birk Inhibitor is effective at stopping the initiation of cancer at a cellular level in the laboratory. Researchers also have found that high levels of soybean consumption are associated with lowered rates of colon, breast and prostate cancers.

Oral cancer accounts for about 30,000 cancers diagnosed annually in the United States. Only half of those patients diagnosed are alive five years later, according to the U.S. Centers for Disease Control. While survival rates in breast, colon and prostate cancers have improved, oral cancer survival has shown no improvement in the past two decades and has actually worsened among some minority groups. In some areas, such as Sri Lanka, India and Southeast Asia, incidence rates are at more than 40 percent of all cancers, compared to a rate of about 3 percent in the United States. About 75 percent of oral cancers are attributed to the use of tobacco.

"Current treatments for oral cancer are expensive and often require chemotherapy, radiation or surgery," Meyskens said. "Comparatively, oral leukoplakia is far easier to treat. If further trials with Bowman-Birk Inhibitor are successful, they could lead to better prevention methods to keep leukoplakia from growing and preventing this cancer from occurring in the first place."

Meyskens' group is working on further clinical trials on Bowman-Birk Inhibitor's effectiveness. If this and other trials are successful, Bowman-Birk Inhibitor could be developed as a preventive agent against precancerous lesions in the mouth. The researchers currently are recruiting participants for these clinical studies at UCI and at UCLA. Those interested in participating should call Westley Lagerberg, (714) 456-6485.

Meyskens' and Armstrong's colleagues in the study included Thomas Taylor, Quoc A. Nguyen and Westley Lagerberg of UCI; Jerald Jensen and Wayne Thompson of the Veterans Affairs Medical Center, Long Beach; and Ann R. Kennedy and X. Steven Wan of the University of Pennsylvania.