Cancer cells carry four times more DNA damage than healthy tissue

A new study compared the number of genetic errors, so-called somatic mutations (DNA changes that are not inherited but arise during life), in normal cells and cancer cells from five different organs. The finding: cancer cells contain on average four times as many mutations as healthy cells from the same organ.

That finding itself is not entirely new. But the researchers added a striking observation: even the normal cells of cancer patients contain more mutations than the normal cells of healthy individuals. This suggests that some people have an inherently higher mutation rate. And those who accumulate mutations faster have a greater chance that the wrong combination of mutations will occur by chance in the same cell.

The ‘tail hypothesis’: baseline mutation rate matters

The researchers tested three explanations for the higher mutation count in cancer cells. The most compelling is the so-called tail hypothesis: people at the extremes of the normal distribution of mutation rates, meaning those whose cells inherently accumulate DNA errors faster, are more likely to develop cancer. This offers a new lens on cancer prevention: not only exposure to harmful substances matters, but also an individual’s baseline rate of DNA damage.

What this says about aging and cancer risk

Cancer is largely a disease of aging: risk increases sharply with age, partly because cells accumulate more mutations over a lifetime. This study adds a layer: not everyone accumulates mutations at the same rate. Whether an individual’s mutation rate is measurable or modifiable is an open question for future research. The study was published in the journal Cancer Research.

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