Carl Zimmer in The New York Times:
Elephants ought to get a lot of cancer. They’re huge animals, weighing as much as eight tons. It takes a lot of cells to make up that much elephant. All of those cells arose from a single fertilized egg, and each time a cell divides, there’s a chance that it will gain a mutation — one that may lead to cancer. Strangely, however, elephants aren’t more prone to cancer than smaller animals. Some research even suggests they get less cancer than humans do. On Tuesday, a team of researchers reported what may be a partial solution to that mystery: Elephants protect themselves with a unique gene that aggressively kills off cells whose DNA has been damaged. Somewhere in the course of evolution, the gene had become dormant. But somehow it was resurrected, a bit of zombie DNA that has proved particularly useful.
…Some of the first research focused on a well-studied anticancer gene called p53. It makes a protein that can sense when DNA gets damaged. In response, the protein switches on a number of other genes. A cell may respond by repairing its broken genes, or it may commit suicide, so that its descendants will not have the chance to gain even more mutations. In 2015, Dr. Lynch and his colleagues discovered that elephants have evolved unusual p53 genes. While we only have one copy of the gene, elephants have 20 copies. Researchers at the University of Utah independently made the same discovery. Both teams observed that the elephant’s swarm of p53 genes responds aggressively to DNA damage. Their bodies don’t bother with repairing cells — they only orchestrate the damaged cell’s death. Dr. Lynch and his colleagues continued their search for cancer-fighting genes, and they soon encountered another one, called LIF6, that only elephants seem to possess. In response to DNA damage, p53 proteins in elephants switch on LIF6. The cell makes LIF6 proteins, which then wreak havoc.
More here.