The products most closely associated with cows are milk and beef. But European scientists report today in the Proceedings of the National Academy of Sciences that the animals can be bred to generate antitumor drugs. The findings could lead to a novel way of manufacturing antibodies for tumor therapy on a large scale.

Drugs employing antibodies that recognize proteins found only on cancerous cells tend to work more effectively when paired with a second type of antibody that targets immune cells. But these so-called bispecific antibodies are difficult to produce, so Gottfried Brem of the University of Veterinary Medicine in Vienna and his colleagues tried a new approach. The researchers first linked two genes, one that targets human melanoma cells and one that activates T cells, and inserted the resulting genetic sequence into cow embryos. The nine animals that developed (see image) had high levels of the desired designer antibody, called r28M, in their bloodstreams. The scientists were able to extract and purify significant quantities of r28M, and test it against human melanoma cells. According to the report, the protein is stable and successfully targeted and killed cancer cells in laboratory tests.

The authors suggest that this gene farming approach could be tailored to produce a variety of proteins. Their results, they conclude, emphasize "the fact that blood cells can be directed to produce high concentrations of fully active therapeutic molecules that are otherwise difficult to express."