parallel_prankster writes "In the research published Wednesday, doctors at the University of Pennsylvania say the treatment made the most common type of leukemia completely disappear in two of the patients and reduced it by 70 percent in the third. In each of the patients as much as five pounds of cancerous tissue completely melted away in a few weeks, and a year later it is still gone. The results of the preliminary test “exceeded our wildest expectations,” says immunologist Dr. Carl June a member of the Abramson Cancer Center's research team. Using a modified, harmless version of HIV, the virus that causes AIDS, they inserted a series of genes into the white blood cells. These were designed to make to cells target and kill the cancer cells. After growing a large batch of the genetically engineered white blood cells, the doctors injected them back into the patients."