Tumor nanotrap
By Lydialyle Gibson
Image courtesy Argonne National Laboratory
Brain tumors are among the most stubborn and aggressive of cancers, often defying treatment and leaving patients with only weeks or months to live. Particularly devastating is glioblastoma multiforme (GBM). It starts in the nervous system’s glial cells, which surround and support the neurons, and spreads rapidly to other parts of the brain. The disease is the most common type of primary brain tumor, and 84 percent of patients diagnosed with it die within five years.
Researchers at Chicago and Argonne hope to better those odds. They’re testing a therapy that uses nanotechnology and ultraviolet light to target and destroy tumor cells without damaging healthy tissue. The researchers started with nanoparticles of titanium dioxide, a compound used in sunscreens, food-coloring, paints, and self-cleaning windows. Titanium dioxide binds readily to biological molecules and is a photocatalyst—meaning, when exposed to light, it generates free radicals, unstable atoms that break down the organic molecules around them. To get the compound to fasten itself to GBM cells, Argonne scientists attached an antibody that fits into a GBM surface protein. When the researchers turned on the UV light, the titanium dioxide’s free radicals disrupted the tumor cells’ internal pathways and triggered their self-destruction. The image above illustrates that cell death, when the membrane falls apart and phosphatidylserine (PS), an internal-membrane lipid, moves to the cell’s exterior (researchers use a protein called annexin V to detect PS).
So far, the scientists—who include Chicago neurosurgery research associate Ilya Ulasov and Maciej Lesniak, director of neurosurgical oncology at the University’s Brain Tumor Center—have tested the titanium-dioxide therapy only in the lab. But the results, reported in the September 9 Nano Letters, are promising. When exposed to light for five minutes and allowed to incubate for six hours, nearly 80 percent of GBM cells died. About 15 percent of healthy cells also were ensnared and destroyed, a toxicity rate about the same as existing treatments. The next step is testing the method in animals.