Plants and marine life battle cancer.

It might seem unusual that compounds found in tree bark, sea sponges, or ornamental shrubs can fight cancer, or that plant leaves can kill pain or relieve the symptoms of congestive heart failure. Nevertheless, drugs such as Taxol, which comes from the bark of the Pacific yew tree and is highly successful in fighting ovarian cancer, may be the hope of the future in treating various forms of cancer and other health conditions.

"Hundreds of years ago - even before physicians knew why they worked-many plants and organisms were used to treat certain medical conditions," indicates Robert Mannel, a gynegologic oncologist at the University of Oklahoma Health Sciences Center. "People with congestive heart failure, or `dropsy' as it was called, chewed on foxglove leaves because it got rid of excess fluid." Other, more recent, examples of natural products used to combat illness include penicillin, derived from bread mold, to treat infection, and pain killers such as morphine and opium, which come from the poppy flower.

"Many of medicine's most effective compounds have their origin in nature-either plants, fungus, or animals. So when we look for compounds that are going to be effective against cancer, we want to make sure we look at natural products."

Certain leukemias and gynecologic cancers such as ovarian, uterine, cervical, or vaginal cancers respond well to compounds originating from natural products. Taxol and anti-cancer agents from ornamental shrubs (called vinca alkaloids) affect the cancer cells internal skeleton, making cell division unsuccessful, while marine sponge and fungus compounds attack cancer via other mechanisms.

"The future holds some exciting things in this area," Mannel notes. "We have a much better appreciation of the mechanisms by which natural anti-cancer compounds work, so we can search for compounds with similar structures. We also are better able to synthesize these compounds, so we can develop similar man-made products instead of depleting the Earth of products that may be in limited supply. Computer technology and automation also are helping to speed up the screening process. The [National Cancer Institute] continues to screen organisms from all over the. world - plants from the rainforests, coral reefs in the ocean, and fungi from the soil. The screening program has to go on, because if it doesn't, we're eventually going to miss something novel that's going to be very active against cancer, such as Taxol, which never would have been discovered otherwise."