Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey
Speaker 1: brain Stuff, Lauren Bobo bam here. You have no idea
Speaker 1: what your DNA is up to right now. You might
Speaker 1: not be able to see or feel it working, but
Speaker 1: it is there, It never sleeps, and it's basically got
Speaker 1: you hog tied. Your genetic material is an entire universe
Speaker 1: of biological instructions, and a lot of the time they're
Speaker 1: not even very good instructions. Your DNA could be making
Speaker 1: coarse black hairs grow out of your palms right now,
Speaker 1: or it could be nonchalantly protecting you from cancer. There's
Speaker 1: no telling. Here's the thing, evolution doesn't have some great
Speaker 1: plan for you personally, whether or not you have genes
Speaker 1: that tell your palms to grow whiskers or your body
Speaker 1: to fight cancer. That's mostly just happenstance, mostly, but from
Speaker 1: time to time, DNA has been known to pull incredible
Speaker 1: hail Mary's Take elephants, for instance, they very rarely get cancer.
Speaker 1: An elephants cancer mortality rate is just under five percent.
Speaker 1: For US humans it's between eleven and twenty five. Whales
Speaker 1: have very low rates of cancer too. In fact, large
Speaker 1: animals of all kinds seem to succumb to cancer way
Speaker 1: less than one might imagine. This puzzled cancer researchers in
Speaker 1: the nineteen fifties and sixties because the early understanding of
Speaker 1: why cancer happens has to do with how many cells
Speaker 1: an animal has, coupled with its longevity. Large and long
Speaker 1: lived animals, scientists theorized, have lots of cells and more
Speaker 1: time in which cells could potentially start doing their jobs wrong. Conversely,
Speaker 1: small animals have fewer cells and generally don't live as
Speaker 1: long as larger animals. Thus there are fewer chances and
Speaker 1: less time for cells to mutate in the ways that
Speaker 1: would result in cancer. This line of reasoning makes a
Speaker 1: good bit of sense, right Yet in the nine seven these,
Speaker 1: statistical epidemiologist Richard Peto observed that we don't see a
Speaker 1: higher instance of cancer in humans than we do in mice,
Speaker 1: even though human bodies contain a thousand times more cells
Speaker 1: and we live thirty times as long. And so science
Speaker 1: was introduced to Peto's paradox, the mystery that's bedeviled cancer
Speaker 1: researchers for nearly half a century. Even though cancer reliably
Speaker 1: shows up in larger individuals within a species more often
Speaker 1: than in smaller ones. For instance, just a couple inches
Speaker 1: of height on a human can significantly raise her chances
Speaker 1: of getting some types of cancer. For whatever reason, huge
Speaker 1: and long lived animals have cancer rates comparable to or
Speaker 1: lower than our own. Because being humongous has evolved in
Speaker 1: various animals countless times over the eons, there are probably
Speaker 1: as many solutions to Peto's paradox as there are gigantic animals. However,
Speaker 1: a study published in an August issue of Cell Reports
Speaker 1: found the reason for Peto's paradox and elephants is in
Speaker 1: reality completely bonkers genetically speaking. Previous research reported that African
Speaker 1: savannah elephants have a whole bunch of copies of a
Speaker 1: specific cancer fighting gene called t P fifty three. This
Speaker 1: gene produces a protein that comb cells looking for potential
Speaker 1: DNA damage. Humans and most other animals have only one
Speaker 1: copy of this gene. Elephants, it happens, have twenty copies.
Speaker 1: So t P fifty three lends the elephant a lot
Speaker 1: of capacity to see that there is a problem, but
Speaker 1: not really the ability to do anything about it. So
Speaker 1: the University of Chicago research team rummaged around and the
Speaker 1: elephant genome to see if they could find any clue
Speaker 1: as to what would be carrying out the cell repairs
Speaker 1: or cell destruction that gives elephants their cancer fighting powers,
Speaker 1: and they found something pretty obvious. Elephants have between seven
Speaker 1: and eleven copies of a type of gene known as
Speaker 1: leukemia inhibitory factor, or l i F. The problem was
Speaker 1: these copies were evolutionarily old, and many of them had
Speaker 1: probably been useful to the elephants distant ancestors, but they
Speaker 1: were so degraded that they were probably useless. But this
Speaker 1: is where things start getting weird. For the article this
Speaker 1: episode is based on how Stuff Work. Spoke with the
Speaker 1: studies lead author one Manuel of as Quez, then a
Speaker 1: graduate student in the Department of Human Genetics at the
Speaker 1: University of Chicago. He said, well, what we actually found
Speaker 1: was a copy of l i F l i F six,
Speaker 1: which had integrated into the genome in the common ancestor
Speaker 1: of elephants and manatees. Manatees still have this piece of DNA,
Speaker 1: but it's what would traditionally consider junk. But elephants took
Speaker 1: this junk DNA and right before law lost any in
Speaker 1: all coding potential for the correct protein. It evolved a
Speaker 1: new way of inducing its activation and expression into a
Speaker 1: functional protein. Again, it was pure luck. So as a
Speaker 1: last ditch attempt to cut down on the accumulation of
Speaker 1: bad cells, the elephant's body resurrected a piece of DNA
Speaker 1: that's capable of killing cells that have been flagged for
Speaker 1: execution by t P fifty three due to DNA damage
Speaker 1: and put it to work culling those cells. L i
Speaker 1: F six kill cells by poking holes in the mitochondria,
Speaker 1: the power plant of the cell, and you know it
Speaker 1: could have gone wrong. What's amazing is that the elephant
Speaker 1: was able to both reactivate the gene and control it
Speaker 1: to tell l i F six to kill not every cell,
Speaker 1: but just the ones that seemed the most dangerous. You
Speaker 1: can't control your DNA, but sometimes it can come out
Speaker 1: with some pretty good tricks you'd never even think of.
Speaker 1: Today's episode is based on the article Zombie Jeane protects
Speaker 1: Elephants from cancer on House Tofworks dot Com, written by
Speaker 1: Jesslyn Shield. Brain Stuff is production of I Heart Radio
Speaker 1: in partnership with housetuffworks dot Com, and it's produced by
Speaker 1: Tyler Clang. Four more podcasts on my heart Radio, visit
Speaker 1: the iHeart Radio app, Apple podcasts, or wherever you listen
Speaker 1: to your favorite shows.