Meanwhile, a neurotoxin from the venom of the giant deathstalker scorpion has been found to attach to the surface of brain cancer cells. The overwhelming reason tumors come back is that surgeons can’t reliably distinguish good cells from bad at the growths’ edges. Magnetic resonance imaging—the best available diagnostic tool—doesn’t detect masses smaller than about a billion cells. This means surgeons have to find the boundaries between tumors and healthy tissue “purely by visual and textural cues,” says James Olson of the Fred Hutchinson Cancer Research Center in Seattle, Washington. “It’s a very imperfect science. Glioma cells weave into normal tissue, and pieces sometimes get left behind.”
Doctors who treat glioma, the most common form of brain cancer, created a “molecular flashlight” by marking chlorotoxin with a near-infrared dye. On the very first trial, Olson says, the “tumor paint,” as he calls the scorpion-derived marker, “lit up the cancer beautifully. We were literally jumping up and down because we knew what incredible potential this had.” The paint reveals masses with as few as 200 tumor cells. “You can truly see the tumor almost cell by cell,” Olson says. “This will let surgeons get more cancer out, maybe even 100 percent.” Human trials on the dyed toxin will start later this year, and if tests go well, the paint could be used for prostate, colorectal, lung, breast, pancreatic, and skin cancers, as well as glioma, potentially saving or prolonging millions of lives every year.