The findings, along with similar work on elephants, suggest that somewhere, hiding in the genetic code and evolutionary history of large mammals, there could be a new cancer treatment for humans. But the researchers’ window to study these megafauna may be closing, as humans continue to threaten the animals’ populations and the biodiversity of their habitats.
Read: Elephants have a secret weapon against cancer
That whales like Salt had value was never in doubt for Robbins. There are many valid reasons to conserve large mammals, from the ethical to the ecological. But the idea that their genes could be useful for cancer research was a new one for her.
“I did not think years ago that one of the things we would be studying with this population would be cancer, in general, let alone any kinds of cancer implications for humans,” she says. “It’s unexpected, and very valuable, but I never would have planned it.”
In theory, large, long-lived creatures like Salt should have high cancer rates. At its core, cancer begins when a cell splits—it divides incorrectly, and the potentially fatal mutation spreads to neighboring cells, and, if left unchecked, throughout the body.
Compared with humans, whales and elephants can have hundreds of times the number of cells—and have similarly long natural life spans—but their cells mutate, become cancerous, and kill them less frequently. This quirk of nature, which the ACE team is studying, is called Peto’s Paradox, named for Richard Peto, a British epidemiologist. In the late 1970s, he proposed that there must be some kind of natural selection for cancer suppression, because humans live longer and are much larger than mice, but the species have similar rates of the disease.
In 2011, by comparing the information in Salt’s genes to those of other cetaceans, ACE researchers, along with scientists at 11 other institutions worldwide, started looking at how Peto’s Paradox manifests itself in the genomes of humpback whales. According to the results reported this year, the parts of a whale’s genome that determine how and when a cell splits evolved quickly and coincided with when the animals grew to their enormous size. Marc Tollis—a biologist at Northern Arizona University’s School of Informatics, Computing, and Cyber Systems who joined and began leading the ACE study in 2015—hopes that taking one of the amped-up, cancer-fighting whale genes and putting it in the body of a smaller creature will help the latter fight off these cellular mutations: a mouse as a test, a human as an aspirational end result.
Other scientists are also studying Peto’s Paradox in a different group of huge animals: elephants. In 2012, Joshua Schiffman, a pediatric oncologist at the University of Utah, began investigating cancer defenses in the animals after learning that they had extra copies of a gene responsible for fighting off tumors. It was this same gene that he found lacking in his patients with Li-Fraumeni syndrome, a rare hereditary disorder that predisposes those who have it to cancer development.