Mutations increase cancer risk

From CNN:

For the first time, researchers have estimated what percentage of cancer mutations are due to environmental and lifestyle factors, hereditary factors and random chance. Overall, 66% of the genetic mutations that develop into cancer are caused by simple random errors occurring when cells replace themselves, according to a new study published in the journal Science.

Environmental factors contribute 29% of mutations, while the remaining 5% are inherited, say Cristian Tomasetti and Dr. Bert Vogelstein, both of Johns Hopkins University.
In a previous paper, Tomasetti and Vogelstein asserted that your risk of developing cancer is largely based on random DNA errors that occur when self-renewing cells divide. In their new paper, they offer more detail describing how dumb luck plays a more significant role than either environmental, lifestyle or hereditary factors in causing this disease.
“Every time a perfectly normal cell divides, as you all know, it makes several mistakes — mutations,” explained Vogelstein in a briefing. “Now most of the time, these mutations don’t do any harm. They occur in junk DNA, genes unrelated to cancer, unimportant places with respect to cancer. That’s the usual situation and that’s good luck.”
Occasionally, one of these random miscopies will occur in a cancer driving gene.
“That’s bad luck,” said Vogelstein.
Though this fact may be demoralizing to some people, researchers noted it might bring comfort to people with cancers they worked to prevent or the parents of children with cancer.

Your lifestyle still matters

In a previous research paper published in 2015, Tomasetti and Vogelstein used a mathematical model to first present this idea that cancer risk is strongly correlated with the total number of divisions undergone by normal cells. For 31 cancers, the researchers first estimated the number of stem cells in tissues where disease arose and then they estimated the rate at which these cells divide. Comparing these to incidence of these cancers in the United States, the two researchers found a strong correlation between cell division and lifetime risk of each given cancer.
For their new study, Tomasetti and Vogelstein worked with Lu Li, a doctoral student at Johns Hopkins Bloomberg School of Public Health, to analyze genome sequencing and epidemiologic data from 32 cancer types, including breast and prostate cancers. This time, the research team concluded that nearly two-thirds of mutations in these cancers are attributable to random errors that occur naturally in healthy, dividing cells during DNA replication.
Even mutations caused by environmental or lifestyle factors are haphazard, explained Tomasetti.
Take smoking: Cigarette smoking undoubtedly leads to more genetic mutations than might normally happen, yet where the DNA defects occur on a smoker’s genome is completely accidental. In other words, mutations caused by smoking, just like random mutations, can affect either cancer driving genes or stretches of DNA that are irrelevant to cancer.
Lifestyle factors still matter for cancer prevention.

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