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Cells that heal fastest risk cancer
Kids heal ridiculously fast. A cut a parent still sees as a scab four weeks later is gone from a child in three days. A Stanford group studies this, and wound healing in the young is quite a bit faster and more efficient at many levels.
In an adult, a gap left by dying cells gets filled by the cells fittest to replicate, and the fittest are often cells with a mutation that makes them divide a bit faster. Winning that way selects for cells that drift a little out of range on growth.
A little better at growing helps close a scratch. Much better, and the cells grow into a lesion and spread to other places, which is called metastasis and is how most people die of cancer.
Why do children heal wounds so quickly?
Young skin has more actively dividing cells, and its supporting cells respond strongly to growth signals. Fetal skin goes further and can heal with almost no scar, which has made it a model for wound research. Adult wounds heal with more scar tissue, which is stiffer and less organized than the original skin. Healing speed and scarring are tied together in the same repair system.
How can a mutation help skin cells win a wound?
Cells that divide a little faster take up more of the empty space, so their descendants make up a larger share of the repaired tissue. A 2018 study in Science by Inigo Martincorena and colleagues found that by middle age, normal esophageal lining is a patchwork of mutant clones, with mutations in the NOTCH1 gene especially common. The mutant clones had expanded because they out-competed neighbors for space. Most of these clones do not become cancer.
How does cancer spread to other organs?
To spread, a tumor cell has to detach from its neighbors, enter the blood or lymph, survive the trip, and settle in a new organ. Most cells that enter the bloodstream die along the way. Surviving cells can sometimes lie dormant in a new organ for years before growing. A 2011 review by Christine Chaffer and Robert Weinberg noted that metastasis accounts for about 90 percent of cancer deaths.
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