A Zombie Gene Protects Elephants From Cancer

• Viviane Callier

Modern and extinct elephants evolved many features to support the colossal bulk of their bodies. These adaptations include special genetic mechanisms that make them less susceptible to cancer. E. Timothy Paine

Elephants and other large animals have a lower incidence of cancer than would be expected statistically, suggesting that they have evolved ways to protect themselves against the disease. A new study reveals how elephants do it: An old gene that was no longer functional was recycled from the vast “genome junkyard” to increase the sensitivity of elephant cells to DNA damage, enabling them to cull potentially cancerous cells early.

In multicellular animals, cells go through many cycles of growth and division. At each division, cells copy their entire genome, and inevitably a few mistakes creep in. Some of those mutations can lead to cancer. One might think that animals with larger bodies and longer lives would therefore have a greater risk of developing cancer. But that’s not what researchers see when they compare species across a wide range of body sizes: The incidence of cancer does not appear to correlate with the number of cells in an organism or its lifespan. In fact, researchers find that larger, longer-lived mammals have fewer cases of cancer. In the 1970s, the cancer epidemiologist Richard Peto, now a professor of medical statistics and epidemiology at the University of Oxford, articulated this surprising phenomenon, which has come to be known as Peto’s paradox…