NPR - Cancer can be caused by tobacco smoke or by an inherited trait, but new research finds that most of the mutations that lead to cancer crop up naturally.
The authors of the study poked a hornet's nest by suggesting that many cancers are unavoidable.
The provocative findings by Bert Vogelstein and Cristian Tomasetti at the Johns Hopkins Kimmel Cancer Center, have stirred up a heated scientific debate that started two years ago, when they published a report along similar lines.
Back then, critics said they were undercutting important messages about cancer prevention. So when these scientists had new results to report, Vogelstein addressed that concern head-on.
"We all agree that 40 percent of cancers are preventable," he said at a news conference. "The question is, what about the other cancers that aren't known to be preventable?"
Vogelstein, who is also an investigator with the Howard Hughes Medical Institute, explained how he and Tomasetti have refined that question. He notes that every time a perfectly normal cell divides, it makes several mistakes when it copies its DNA. These are naturally occurring mutations.
Most of the time, those mutations are in unimportant bits of DNA. That's good luck. "But occasionally they occur in a cancer driver gene. That's bad luck," Vogelstein says.
After two or three of these driver genes get mutated in the same cell, they can transform that healthy cell into a cancer cell.
In their new paper in Science, the researchers set out to quantify how often those random errors are an inevitable part of cell division, how often they're caused by nasty chemicals like tobacco smoke and how often they're inherited.
The answer: 66 percent of the total mutations are random, about 29 percent are due to the environment and the remaining five percent are due to heredity.