Researchers Know Beans About Cancer Treatment

"We can take ricin, this very potent toxin, and combine it with a monoclonal antibody, a chemical that recognizes the receptor on cancer cells and binds only to that specific cell," said Rial D. Rolfe, Ph.D., chairman of the department of microbiology and immunology at TTUHSC. "When that happens, if ricin is attached to the antibody compound, it will be taken into the cell and kill it. The key is to get it so the ricin only enters the cancer cells."

Commercial production of castor ceased in the United States in the early 1970s, due to the potential health risks of coming in contact with the deadly ricin while harvesting and processing, and associated legal liabilities. Now almost all castor plants are grown in countries such as India and Brazil. Texas Tech's department of plant and soil science in the College of Agricultural Sciences and Natural Resources cultivates a two-acre castor plant field, in hopes of cross-breeding a variety of castor bean that yields high levels of ricin.

"Just two acres of land, given the right castor seed, could produce enough ricin to meet the world's pharmaceutical supply need for cancer treatment," said Dick L. Auld, Ph.D., chairman of Texas Tech's plant and soil science department.

Phase-I human trials using ricin to treat cancer have been ongoing for nearly 10 years, according to Ellen Vitetta, Ph.D., professor of microbiology at the University of Texas Southwestern Medical Center, where testing on cancer patients is currently taking place.

"We have treated between 150 and 200 patients with lymphoma, and I would say about 60 percent of our patients show some evidence of tumor shrinkage, and 30 to 40 percent of those get partial or complete reduction," said Vitetta.

In addition to developing a castor bean with high-ricin content, the department also is trying to design a seed that contains zero or low levels of the toxin, which would reduce health risks for growers and processors and may renew interest among producers for the plant's oil value, Auld said.