Scientists have unravelled the secret to why elephants rarely get cancer despite their large size.Elephants have 38 additional modified copies of a gene that encodes p53, a compound that suppresses tumour formation.
Humans, on the other hand, have only two, according to the study in the Journal of the American Medical Association (JAMA).
This means that as elephants evolved, their bodies made many extra copies of a gene that prevents tumours from forming.
Elephants have been considered an enigma for years because they have far more cells than people, which would presumably place them at higher risk of cancer over their lifespans, which can last 50-70 years.
And yet, the analysis of a large database of elephant deaths showed that less than 5 per cent of elephants die of cancer, compared to 11 to 25 per cent in people.
We think that making more p53 is nature’s way of keeping this species alive.
Dr Joshua Schiffman
“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,” said co-senior author Dr Joshua Schiffman, paediatric oncologist at Huntsman Cancer Institute, University of Utah School of Medicine.
The scientists combed through the African elephant genome and found at least 40 copies of genes that code for p53, a protein well known for its cancer-inhibiting properties.
“We think that making more p53 is nature’s way of keeping this species alive.”
To test their hypothesis, they then compared cells from the elephants with a group of healthy humans, and a group of people who have Li-Fraumeni Syndrome, who have just one copy of p53 and a 90 per cent chance of developing cancer over their lifetime.
Hope for cancer-fighting therapies?
The researchers found that elephants have a more aggressive internal mechanism for killing damaged cells that are at risk for becoming cancerous.
“In isolated elephant cells, this activity is doubled compared to healthy human cells,” said the researchers that included experts from Arizona State University and the Ringling Bros Centre for Elephant Conservation.
The elephant cells self destructed more than five times the rate of those from people with Li-Fraumeni Syndrome.
The researchers hope their findings could one day lead to new cancer-fighting therapies in people.
But that day could be far off, according to Professor Mel Greaves, director of the Centre for Evolution and Cancer at The Institute of Cancer Research, London.
“The new research provides a plausible answer to one of the most celebrated riddles in evolutionary biology — why some big animals with lots of cells still manage to have quite low rates of cancer,” said Professor Greaves, who was not involved in the study.
“It is not immediately clear what lessons there are from this elephant tale for risk of cancer in humans. The main impact of this remarkable story is to bring into focus the question of why we are so uniquely predisposed to cancer for our size and lifespan — and what we can do to change this.”
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