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Scientists knew that it was possible that the skin was peculiar. Perhaps inside the body, protected from ultraviolet light, were healthy cells that did not carry these key mutations.
To find out, the researchers decided to study the cells of the esophagus. The team collected tissue samples from nine deceased healthy organ donors, cut them into several dozen squares and examined the same 74 cancer-related genes.
Dr. Martincorena and his colleagues found that new mutations appeared more slowly in the esophagus than in the skin. But once these mutations emerged, they caused the esophagus cells to grow more rapidly than normal esophageal cells. Over time, these dishonest cells have spread into the esophagus, forming colonies of mutant cells, called clones. Although these clones are not cancers, they have one of the characteristics of cancer: rapid growth.
"These mutant clones colonize more than half of your esophagus in middle age," said Dr. Martincorena. "It opened my eyes." Dr. Martincorena and his colleagues reported their findings Thursday in the journal Science.
By examining mutations, researchers were able to eliminate external causes, such as tobacco smoke or alcohol. Instead, the mutations appear to have appeared during ordinary aging. As the cells divide again and again, their DNA is sometimes damaged. In other words, the rise of these mutations may well be an intrinsic element of aging.
"It seems that no matter how much you take care of yourself by eating well, exercising and limiting certain vices, there is probably a lot to do against the need for it. Organism to replace its cells, said Scott Kennedy, a cancer. a biologist from the University of Washington who did not participate in the study.
The study also raised questions about efforts to detect cancer early, while cancer cells are still rare, said Dr. Kennedy: "The fact that mutations are badociated with cancer does not mean that they have cancer. "
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