Like a virus, the polymer (known as polyethylenimine, or PEI) is able to travel throughout the body, carrying genes - in this case, suicide genes - and transferring them into targeted cells. Children's Hospital co-investigators WT Godbey, PhD, and Anthony Atala, MD, engineered the polymer to recognize and target tumor cells based on their over-secretion of a protein known as COX-2. They worked with several cancers of the genitourinary system that over-secrete the COX-2 protein, including prostate and bladder carcinomas.

Because normal cells secrete little or no COX-2, they are spared. ''When you give chemotherapy or radiation therapy, you're attacking not only the tumor, but also normal cells,'' explains Atala. ''But when we induce cell death with this technique, it's only being induced in cells that are secreting COX-2 at high levels. We can really turn up the ability to kill these tumors without worrying about killing the good cells.''

Godbey and Atala presented their findings at the American Academy of Pediatrics annual meeting in New Orleans. They are conducting further studies in experimental models of cancer that are so far yielding promising results.