By Jocelyn Selim
Once upon a time, researchers believed viruses triggered many cancers; after years of doubt, they are starting to think so again
By Jocelyn Selim
Toward the end of 1910, a newly minted researcher named Peyton Rous was testing out a highly unlikely hunch about the origin of some cancers.
Only two years out of medical school, Rous had declared himself unfit to be a “real doctor” and vowed instead to devote himself to medical research. He had recently landed his first real job, heading the cancer laboratory at New York City’s Rockefeller Institute for Medical Research. The lab’s former director had left the field of cancer to study polio—a disease with more promise for quick vaccines, successful treatment and glory.
At the time, doctors were just beginning to understand that exposure to certain compounds could cause cancer—soot was blamed for high cancer rates among chimney sweeps and frequent work with X-ray machines was linked to aggressive tumors of the hands. Still, cancer was mostly a mystery: A puzzlingly spontaneous occurrence, albeit one that could be hastened by exposure to certain carcinogens.
Rous’ hunch was unusual for the time. Was it possible to “catch” cancer, he wondered, like one would catch a cold? Like many other researchers, he was fascinated with infections. The decades after Robert Koch announced in a landmark 1882 lecture that he had connected tuberculosis to a type of bacteria ushered in a golden age of infectious disease research. Koch followed his surprising assertion with news that he had found the cholera bacterium. And using Koch’s methods, researchers were able to definitively prove, with near-dizzying speed, the organisms responsible for diseases like diphtheria, typhoid, tetanus, syphilis and even bubonic plague. Infectious disease research was the place to be.
Rous, now at Rockefeller, decided to test the prevailing scientific view of cancer, which focused on physical and chemical insults to the body, not infectious ones. Using a Plymouth Rock hen that had a large tumor on its chest, Rous developed a simple experiment: He extracted tumor cells and passed them through a filter so fine that even bacteria were kept out, and then injected the filtered fluid into healthy chickens. A few weeks later, tumors appeared, clustered around the injection sites of the healthy chickens. Rous had found the first virus that causes solid tumors in animals: the Rous sarcoma virus (RSV).
His results, published in the Journal of Experimental Medicine, were reported by the New York Times. But the publicity wasn’t enough to give credibility to the finding, which other cancer researchers roundly dismissed as either insignificant or an exotic curiosity. (Viruses were new to science: The first had been identified less than two decades earlier.) Rous wasn’t swayed, and continued his experiments with other types of chicken tumor cells, discovering that the filtered fluid from each cell type (bone, cartilage, blood vessels) produced tumors when injected into healthy animals. His results continued to be ignored, but Rous was convinced: Viruses cause some cancers. And if a virus could cause cancer in chickens, why not in humans?
Early Clues to Elusive Viruses
“The idea that cancer is a viral disease really goes back to Peyton Rous,” says surgical oncologist H. Kim Lyerly, the director of the Duke Comprehensive Cancer Center in Durham, N.C. “But Rous didn’t really have the tools to see what was happening. It’s a bit like Galileo’s great folly. When he was looking through his telescope, he thought Saturn was actually three planets. He didn’t have the optics to see the rings. And he couldn’t even conceive of rings, because no one had ever imagined them before. In terms of cancers and viruses, that’s the area we’re just getting into now.”