*intro*
The antlers of deer, moose, and elk grow ridiculously fast. Uniquely fast, actually. 

Among mammals, they're the only body parts that can regenerate completely and they do, regrowing year after year from just a small stump.

So you would think with all those cells whose job is to divide really fast that animals in the deer family would get cancer more often than others. But deer actually get cancer less. Way less, like one-fifth as often as other mammals at least based on statistics from animals in captivity.

And a massive 2019 genome study might have revealed why. In a paper published in the journal Science, researchers analyzed the genomes of certain species of deer, along with dozens of related species. And the genetic changes they found in the deer DNA go a long way toward explaining both how antlers grow so fast and how that growth doesn't lead to cancer more often. 

Usually, cells growing and dividing too fast is a problem. When cell growth escapes the body's control, those cells can form a tumor. Cancer is what happens when those uncontrolled cells become malignant, capable of escaping to other parts of the body and causing extra cell division there too. 

With their super fast growth, antlers bear some resemblance to tumors. In fact, the 2019 study found that in terms of what genes they express, antler cells are more like bone cancer than regular bone. That includes genetic changes that promote cell growth and division. 

And based on what we know from studies in other species, similar changes can often cause cancer if left unchecked.

For example, antler cells express a lot of a gene called Fos, meaning they contain more of that gene's protein product than you'd normally expect. And Fos instructs cells to grow and divide more. That should be a big risk, cancer-wise.

Usually it takes a bunch of problematic genes working together to cause cancer, but in mouse studies, over-expressing just this one gene is enough to cause bone cancer. Any cancer biologist will tell you that Fos is really, really mean. And deer strongly express Fos and a bunch of other genes that can lead to cancer. 

But, it turns out deer also have genetic changes to keep all that extra cell division from turning into cancer, mainly involving P53, sometimes known as the master tumor suppressor. P53 makes a protein that checks cells for DNA damage. If the damage is fixable, the P53 protein tells the cell to repair it. If it's not fixable, it makes the cell self-destruct.

Elephants, which also have very low cancer rates, have extra copies of the P53 gene in their DNA. Researchers think that's a big part of what makes them less prone to cancer. 

Deer don't have extra copies. Instead, they've evolved more genes to support what P53 does and help it along. They've also evolved a bunch of other tumor suppressor genes, specifically expressed in their antlers.

The researchers suggest that these two sets of genetic changes might have evolved together. Growing antlers helped attract mates which was good because babies, but it also involved genetic changes that led to super fast cell division, which was bad, because cancer.

In the end, they evolved a complex set of mechanisms to let antler cells grow and divide really fast, while keeping everything tightly controlled. So, scientists seem to have their answer to why deer don't get cancer more often. And the hope is that maybe with more research into these mechanisms, we'll get a little closer to preventing cancer in humans too. 

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*outro*