Other scientists have been examining non-nutritive compounds in plants. Elson has been studying compounds he calls isoprenoids, a group that includes more than 22,000 compounds. All are derived from a parent compound called mevalonic acid. Limonene and lycopene are examples of isoprenoids that inhibit cancer.
Many isoprenoids contribute to plants' distinctive flavors and fragrances, Elson says. In plants, isoprenoids help regulate germination, growth, flowering, and dormancy while attracting pollinators and protecting plants from insects and fungi.
Elson began working with isoprenoids because some can reduce cholesterol levels in animals. Initially he hoped that depriving tumor cells of cholesterol would make them susceptible to cancer treatments. But Elson's early experiments showed he could not lower the cholesterol in tumor cells by feeding animals isoprenoids. However, he noticed that the isoprenoids slowed tumor growth.
To screen isoprenoids for those with anticarcinogenic activity, Elson tests them against a cell line developed from an extremely aggressive form of mouse melanoma. He has identified many isoprenoids that can slow the growth of this cell line. The tricky part has been finding isoprenoids that suppress cancer growth at the low concentrations that might occur in diets.
One such isoprenoid is gamma-tocotrienol, a compound found in cereal grains; it has a chemical structure related to vitamin E. In research published in 1997, Elson's group showed that substituting gamma-tocotrienol for vitamin E in a diet fed to mice slowed the growth of tumors transplanted to those mice. It was the first research demonstrating that an isoprenoid slowed cancer growth and prolonged the life of mice when fed at a level that an animal might consume.
In the current paper, Elson and his graduate student, Huanbiao Mo, found that
Contact: Charles Elson
University of Wisconsin-Madison