Elephants can live to be 70 years old, and have 100 times as many cells as humans. While this long lifespan and abundance of cells typically means more chances for cells to mutate into tumors, the animals very rarely get cancer.
Peto’s Paradox is the observation by British epidemiologist Richard Peto that cancer risk does not always correlate with a species’ size or lifespan. Some animals, like the elephant and the naked mole rat, have developed very powerful anti-cancer strategies that keep their risk extremely low. Meanwhile, certain species such as dogs, mice, and cheetahs are much more vulnerable to the disease. Researchers believe that studying these patterns in animals may shed light on potential preventative measures or treatment options for humans.
Joshua Schiffman, MD, a pediatric oncologist and cancer researcher at the University of Utah, has been studying variation in cancer rates across species for a decade. He and a team of researchers discovered that elephants have 40 copies of the TP53 gene. Humans and most other animals, meanwhile, only have two copies of the gene.
The TP53 gene helps the body kill rogue cells before they become tumors, but until this point no one knew of a species with so many copies of the gene. These extra copies may give elephants the ability to keep mutant cells at bay, thus significantly reducing cancer rates.
Meanwhile, naked mole rats’ cancer-fighting abilities may be due to their high production of hyaluronic acid, which seems to prevent tumors from growing out of control. Their cousin, the blind mole rat, has also developed an anti-cancer strategy, “concerted cell death”, where cells replicate far fewer times than those of other species. This greatly reduces the risk of cell mutation.
More research is needed to fully understand how certain animals are able to fight off cancer better than others, and what genetic differences can be linked to reduced cancer rates. Eventually, researchers hope it will be possible to use their strategies to develop new ways to fight cancer for humans.