Two thirds of cancers
caused by random genetic mistakes: U.S. study
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[March 24, 2017] By
CHICAGO (Reuters) - About two thirds of
cancers are caused by random typos in DNA that occur as normal cells
make copies of themselves, a finding that helps explain why healthy
individuals who do everything they can to avoid cancer are still
stricken with the disease, U.S. researchers said on Thursday.
"These cancers will occur no matter how perfect the environment,"
said Dr. Bert Vogelstein, a cancer geneticist at Johns Hopkins
University in Baltimore whose study was published in the journal
The new findings are based on genetic sequencing and cancer studies
from 69 countries around the world. They follow a controversial 2015
study published in Science by the same researchers at Johns Hopkins
that looked just at cancers in the United States.
That study, by Vogelstein and mathematician Cristian Tomasetti,
asserted that random DNA mistakes accounted for a lot more of the
risk of developing cancer than previously thought. The finding
caused an outcry from cancer experts, who have traditionally held
that most cancers were caused by preventable lifestyle and
environmental factors or inherited genetic defects.
Although most people know about the hereditary and environmental
causes of cancer, such as smoking, few appreciate the risk from
random mistakes that occur each time a normal cell divides and
copies its DNA into two new cells, Tomasetti said.
Such mistakes are "a potent source of cancer mutations that
historically have been scientifically undervalued," Tomasetti said
in a statement.
The new work offers the first estimate of what proportion of cancers
are caused by these random mistakes. To get there, the team
developed a mathematical model using DNA sequencing data from The
Cancer Genome Atlas and disease data from the Cancer Research UK
database, looking specifically at mutations that drive aberrant cell
growth in 32 different cancer types.
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Although there was variation within specific cancers, overall, the
researchers estimated that 66 percent of mutations in these cancers
resulted from copying errors, 29 percent were caused by lifestyle
and environmental factors, and the remaining 5 percent were
Although most of these mutations cannot be prevented, the team
stressed that early detection and treatment can prevent many cancer
deaths, regardless of the cause.
Though most cancers are due to bad luck, people should not ignore
sound public health advice that can help people avoid preventable
cancers, including maintaining a healthy weight and avoiding
environmental risk factors such as smoking, the team said.
(Reporting by Julie Steenhuysen; Editing by Leslie Adler)
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