When virologist Hilary Koprowski, M.D., reported last month in the Proceedings of the National Academy of Sciences how he and colleagues used tobacco plants to produce cancer-fighting monoclonal antibodies that recognize and hunt down breast and colorectal cancer cells, the work represented another step toward a goal he has been pursuing for the last decade.
While therapeutic uses for such antibodies continue to grow at a rapid rate, production has failed to keep pace. Dr. Koprowski, professor of cancer biology at Jefferson Medical College of Thomas Jefferson University and Jefferson’s Kimmel Cancer Center in Philadelphia, contends that “plants are safer, less expensive and easier to use” than currently used methods in the laboratory and with animals. For mass production purposes, he says, “plants make more sense.”
In the most recent research, Dr. Koprowski, who is also director of the Biotechnology Foundation Laboratories and the Center for Neurovirology at Jefferson Medical College, and his team inserted DNA coding for an antibody against the Lewis Y antigen, which is found on breast and colorectal cancer cells, among other cancers, into tobacco plants. The plants, in turn, become factories churning out antibody. As in their earlier studies, the antibodies were able to kill the cancer cells in the laboratory dish and stop tumor growth in mice. Not only that, these plant-made antibodies worked as well as those produced in the standard way, by mammalian cells. Both types of antibodies suppressed tumor cell growth in mice up to 28 days.
This particular work had an added twist, which has not been shown before: the researchers also demonstrated that the antibodies attached to the human Fc receptor, a key step in the development of immunotherapy. So-called “effector cells” – tumor-cell killing macrophages – recognize monoclonal antibodies through their Fc receptors.
“This technology has all the potential in the world,” Dr. Koprowski says, adding that clinical trials involving plant-produced antibodies should begin to be planned. “It will be the future, and in the next five to 10 years, it could be the main way that therapeutic antibodies are made.”
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