Some organs are more susceptible to cancer than others – and now scientists have offered an explanation.
Dr Frederic Thomas of the Centre for Ecological and Evolutionary Cancer Research in France, and colleagues, look to evolution for the answer, and in particular the idea of each organ having a separate developmental story.
They write in the journal Trends in Cancer yesterday (9 August) that some organs are more vulnerable to cancer due to natural selection, because "humans can tolerate tumours in large or paired organs more easily than in small, critical organs, such as the heart".
Cancers of the colon or breast are not as immediately life-threatening, he writes, so these organs may have evolved fewer mechanisms to defend themselves.
Dr Thomas says: "The organs that are the most important to keeping you alive and capable of reproduction, such as the heart, brain, or uterus, may enjoy a better protection against cancer, all other things being equal. We are not saying that this is the main factor to explain the different susceptibility of organs to cancer, but it is a factor that contributes with others."
Other theories about the rates of cancer in different organs have focused on either risk factors, such as smoking or UV light exposure, or internal factors, such as the frequency of cell division.
Dr Thomas and his team, which includes experts from Australia, suggest that cancer biologists think of individual organs as "specialised islands with their own environmental conditions, such as the level of oxygen, acidity, or water".
The group is now carrying out a long-term experiment to measure the accumulation of cancerous and precancerous mutations inside different organs, using mice.
Thomas, F. et al. Evolutionary Ecology of Organs: a Missing Link in Cancer Development? Trends in Cancer 9 August 2016 [abstract]
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