Strange as it may sound, worms could someday play a key role in fighting cancer. How? Lung cancer cells seem to smell yummy to one species of little worm. Now, scientists are using that allure to build a squirmy new tool to detect cancer. The researchers hope this new “worm-on-a-chip” device will one day provide an easy, painless way to screen for early disease. The cancer-seeking worm in question is the common roundworm, Caenorhabditis elegans. At just about one millimeter (0.04 inch) long, C. elegans is easy to fit on a handheld chip. To build that chip system, researchers crafted what looks like a microscope slide. It has three large indents, or wells. Healthy human cells get placed in a well at one end. Lung cancer cells go in a well at the other end. The worms go in the middle well. From there, they can sniff the cells at either end. In experiments, hungry worms tended to wriggle toward the end containing diseased cells. It’s been reported “that dogs can sniff out people who have lung cancer,” says Paul Bunn. He’s a cancer researcher at the University of Colorado in Aurora who was not involved in the work. “This study,” he says, “is another step in the same direction.” Each chip employs some 50 worms. “About 70 percent of the worms move toward the cancer,” says Shin Sik Choi. He is a biotechnologist that helped develop the worm-on-a-chip system at Myongji University in Seoul, South Korea. With training, Choi suspects the worms’ ability to sniff out cancer can be increased. The Seoul-based team debuted its new worm-on-a-chip on March 20 at the spring meeting of the American Chemical Society. It was held in San Diego, Calif.
Wriggly super sniffers
No one can read a C. elegans worm’s mind. So, it’s impossible to say for sure why these tiny critters find cancer cells appealing. But Choi thinks scent is a pretty safe bet. “In nature,” he explains, “a rotten apple on the ground is the best place where we are able to find the worms.” And cancer cells release many of the same odor molecules as that rotten apple.
C. elegans has a pretty keen sense of smell, says Viola Folli. She studies neuroscience at the Sapienza University of Rome in Italy. Like the Korean team, she investigates C. elegans’ cancer-sniffing prowess. And she’s using what she learns to develop a cancer screening sensor. Although these worms can’t see or hear, Folli notes, they can smell about as well as dogs. In fact, C. elegans has about the same number of genes for chemical-sensing as mammals known for their great sense of smell, such as dogs or mice. That’s pretty impressive, considering C. elegans boast only 302 nerve cells in its entire body — while the human brain alone packs about 86 billion.
Explainer: What is a neuron?
The worms’ simplicity has even allowed scientists to pinpoint the exact nerve cell that reacts to cancer cell aromas. Enrico Lanza, a physicist who studies neuroscience with Folli, did this by genetically tweaking some of the wigglers so that when a specific neuron got activated, it lit up. He then exposed the worms to diseased cells and examined them under a microscope, looking for glow-in-the-dark cells. "C elegans is transparent,” Lanza says. “So if something lights up inside [it]…you can detect it from the outside.” And something did light up — a single, radiant neuron located at one end of C. elegans. Lanza snapped a picture.
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