WASHINGTON, Jan. 19 (UPI) - Scientists have combined the morning-after abortion pill and a bio-engineered cold virus to deliver a genetic switch into the body that can be flipped on to produce therapeutic substances only when needed. Dr. Bert O'Malley, of Houston's Baylor College of Medicine, told United Press International the method opens the door to fighting conditions ranging from cancer to anemia. His experiment produced high levels of human growth hormone in mice without causing an immune response that might destroy the virus. His findings are reported in Tuesday's issue of the Proceedings of the National Academy of sciences.
O'Malley and his team loaded a gutted adenovirus, which usually causes colds, with a segment of DNA that would activate the growth hormone gene and a receptor sensitive to the drug mifepristone, commonly known as RU486, the morning-after pill. After being injected into the body, an extremely low dose of RU486 - thousands of times smaller than is used to disrupt the reproductive system - turned on the gene in the infected liver cells, producing high levels of growth hormone. O'Malley says he chose the growth hormone gene for the experiment because the protein it makes it is easy to track in the body. But he says you can pop the gene out and put in any other DNA segment, such as one that fights cancer or aging.
He plans to try some other proteins this year and hopes to test his virus-and-switch system on humans by 2000. The human experiments will be aimed at cancer, targeting agents that limit tumor proliferation or block blood supply to the cancer. Gene therapy expert Gary Nabel, of Howard Hughes Medical Institute at the University of Michigan, called O'Malley's experiment a major advance. In a commentary accompanying the study, he says he is encouraged by the work, because it can presumably be extended to other vectors to fight other diseases.