Elephants may have saved themselves from extinction by evolving extra copies of a gene that protects against cancer, scientists believe.
A study, published in the Journal of the American Medical Association, has found that the African elephant has 38 extra copies of the p53 gene that helps cancerous cells self-destruct before they form dangerous tumours.
Humans only have two copies of the gene. The multiple ‘back-ups’ mean elephants rarely get cancer, even though such a large and long-living animal should be highly vulnerable to the disease.
Joshua Schiffman, an oncologist at the University of Utah School of Medicine in the US, who co-led the research, said: “By all logical reasoning, elephants should be developing a tremendous amount of cancer, and in fact, should be extinct by now due to such a high risk for cancer. We think that making more p53 is nature’s way of keeping this species alive.”
The gene, nicknamed ‘the guardian of the genome’, produces a protein that can trigger either the rescue or destruction of damaged cells.
On the one hand p53 is able to ‘reboot’ cells and switch on DNA repair mechanisms. Alternatively, it might signal the cell to commit suicide – a process known as apoptosis. If p53 develops a fault it can leave people at the mercy of cancer.
Patients with a condition called Li-Fraumeni Syndrome have only one working copy of p53 and a more than 90 per cent lifetime cancer risk.
Because elephants have 100 times more cells than humans, they should be 100 times more likely to have a cell slip into a cancerous state over a long lifespan of 50 to 70 years. Yet a large analysis of elephant deaths showed that fewer than five per cent of the animals die of cancer, compared with up to a quarter of humans.
The numerous extra copies of p53 genes were discovered when scientists combed through the DNA of the African elephant.
Elephant cells exposed to radiation self-destructed at twice the rate of normal human cells and more than five times the rate of cells taken from Li-Fraumeni patients.
Schiffman said: “If you kill the damaged cell, it’s gone, and it can’t turn into cancer. This may be more effective of an approach to cancer prevention than trying to stop a mutated cell from dividing and not being able to completely repair itself.
“Nature has already figured out how to prevent cancer. It’s up to us to learn how different animals tackle the problem so we can adapt those strategies to prevent cancer in people.”