Nearly Two-Thirds of Cancers Are Due to Random DNA ‘Mistakes’

In this image, the researchers used red coloring to indicate the percentage of cancers that are attributed to inherited mutations (left), random mistakes (center) and environmental factors (right) in women. For each organ, the color represents what percentage is attributable to each factor, ranging from white (0 percent) to red (100 percent). The cancers are identified as: B, brain; Bl, bladder; Br, breast; C, cervical; CR, colorectal; E, esophagus; HN, head and neck; K, kidney; Li, liver; Lk, leukemia; Lu, lung; M, melanoma; NHL, non-Hodgkin lymphoma; O, ovarian; P, pancreas; S, stomach; Th, thyroid; U, uterus.
Credit: C. Tomasetti et al,. Science (2017)

Cancer is caused by mistakes in DNA, and a new study finds that in most cancer cases, these mistakes are completely random; they’re not due to heredity or environmental factors, but rather the result of random errors.

The mistakes, or mutations, cause cancer to happen because even a tiny error in DNA can make cells multiply out of control, the study said. Scientists had thought these mutations resulted mainly from two things: Either the mutation was inherited, or it was caused by outside factors that can damage DNA, such as cigarette smoke or ultraviolet radiation, the researchers wrote.

But a third cause — random mistakes — actually accounts for two-thirds of these mutations, said the new study, published today (March 23) in the journal Science.

When a cell divides, it copies its DNA, so that each of the new cells will have its own version of the genetic material. But each time this copying happens, it creates an opportunity for a mistake to occur. And in some cases, these mistakes can lead to cancer.

This means that cancer “will occur no matter how perfect the environment,” senior study author Dr. Bert Vogelstein, a pathologist at the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University, said in a statement.

In the new study, the researchers wanted to calculate what percentage of cancers were due to heredity, the environment and random mistakes. The scientists developed a mathematical model that incorporated data from registries of cancer patients around the world and data from DNA sequencing.

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