Instead of using some fancy virus, why not just blast genes into cells with a gun? That’s the approach taken by cancer immunologist Wenn Sun of Northwestern University and her colleague Ning-Sun Yang of Agracetus, Inc., in Middleton, Wisconsin. They’ve used a gun powered by pressurized helium to fire microscopic gold bullets, coated with genes, into skin cells surrounding tumors in mice. The cells then produce more of what the genes code for: cytokines, which are messenger molecules that circulate in the blood and activate immune cells. Sun thinks these particular cytokines may activate killer T cells, which poison tumor cells, as well as macrophages, which gobble them up. In any case, she and Yang have found that a week of gene shots three to five times daily not only shrinks the tumors but lengthens the lives of the mice. Unlike viruses, the gene bullets don’t seem to cause inflammation, and the genes they carry aren’t permanently integrated into the cell’s DNA--their effects last only a few days or weeks. That’s a disadvantage when it comes to treating inherited diseases, but it means that diseases like cancer can be treated with less risk of side effects. There’s a fear that with viruses, you create something that hasn’t existed before, with potential consequences that nobody can predict right now, says Sun. Once the Food and Drug Administration approves the gene gun as a medical device, Sun and Yang hope to aim it at human tumors, particularly those beyond the reach of a scalpel.