Elephants rarely get cancer. Here’s why this matters to humans
By Michael Nedelman, CNN
You’d think elephants would be getting cancer left and right: They are giants of the animal kingdom and have trillions more cells than humans — cells that, in theory, could turn into cancer over their decades-long lifespans.
But you’d be wrong. It’s not that they never get cancer, but less than 5% of elephants die from it, versus up to 25% of humans.
“Because of their body size and how many cells they have and how long they live, they should all be developing cancer,” said pediatric oncologist Dr. Joshua Schiffman, professor of pediatrics at University of Utah and an investigator at Huntsman Cancer Institute.
Researchers like Schiffman study animals that have evolved ways to “naturally resist cancer” despite their largeness and longevity, including elephants and bowhead whales. The latter can live for over two centuries.
It’s not just gee-whiz science, either. By picking apart the inner workings of genes and molecules in the animal kingdom, scientists hope to unravel new ways to prevent or even treat cancer in humans.
“This is where the field is moving as a whole,” Schiffman said. “If we can understand how these genomic changes are contributing to … cancer resistance, then we’ll be able to start thinking about how do we translate this to our patients?”
One likely mechanism, according to a paper published Tuesday in the journal Cell Reports, could be a “zombie” gene that, when brought to life by DNA damage, causes that cell to die off.
“If [that cell] kills itself, then that damaged DNA never has the potential to eventually give rise to cancer,” said study author Vincent J. Lynch, an evolutionary biologist at the University of Chicago.
The zombie gene arose from what’s known as a “pseudogene,” a mutated or inactive copy of a normal gene that can accumulate over eons of evolution. Elephants, as well as close living relatives like manatees, have many duplications of a gene known as LIF — but these copies don’t actually work like the original.
In elephants, however, one copy seems to have reanimated and “evolved a new on-off switch” that responds to DNA damage, Lynch said. His study’s findings comprise one piece of a larger puzzle, he added.
“There’s probably lots of things which can contribute to augumented cancer resistance, and we found one of them in elephants,” said Lynch.