The body does not replace worn out cells efficiently but this acts as a defence mechanism against cancer.
Having the neighbouring cell just split into two identical daughter cells would seem to be the simplest way to keep bodies from falling apart. However, according to John W. Pepper of The University of Arizona in Tucson, who led the study, that would be a recipe for uncontrolled growth.
Advertisement"If there were only one cell type in the group, it would act like an evolving population of cells. Individual cells would get better and better at surviving and reproducing," said Pepper, a UA assistant professor of ecology and evolutionary biology and a member of UA's BIO5 Institute.
"When cells reach the point where they divide constantly, instead of only when needed, they are cancer cells," he added.
Pepper said that multicellular organisms use a seemingly inefficient process to replace lost cells. An organ such as the skin calls upon skin-specific stem cells to produce intermediate cells that in turn produce skin cells.
Although great at their job, the new skin cells are evolutionary dead ends. The cells cannot reproduce.
Pepper added that losing the ability to reproduce was part of the evolutionary path single- celled organisms had to take to become multicellular.
As for the single cells, Pepper said: "Probably they got to be part of something more powerful. Something that was hard to eat and good at eating other things."
"Organisms are just a bunch of cells. If you understand the conditions under which they cooperate, you can understand the conditions under which cooperation breaks down. Cancer is a breakdown of cooperation," he added.
In the study, the researchers used a kind of computer model called an agent-based model to compare different modes of cellular reproduction.
The analysis indicated that if cells reproduce by simply making carbon copies of themselves, the cells' descendants are more likely to accumulate mutations. In contrast, if cellular reproduction was much more complicated, the cells' descendants had fewer mutations.
The researchers reported that suppressing mutations, which might fuel uncontrolled growth of cells would be particularly important for larger organisms that had long lives.
The study is published in their paper, "Animal Cell Differentiation Patterns Suppress Somatic Evolution," in the issue of PLoS Computational Biology.
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