Big animals like elephants live longer and their cells have to divide more, so you would expect them to be more susceptible to cancer. People who inherit one copy that doesn’t work may develop a condition called Li-Fraumeni syndrome, which gives them a greater than 90 percent risk of getting cancer during their lifetime, according to the study, published online today (Oct. 8) in the journal JAMA. Center for Elephant Conservation, elephants have 38 additional modified copies (alleles) of a gene that encodes p53, a well-defined tumor suppressor, as compared to humans, who have only two. These two animals, as well as elephants, do share a strategy of genetically killing off damaged cells.
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Dr Schiffman added: “Nature has already figured out how to prevent cancer”.
“The enormous mass, extended life span and reproductive advantage of older elephants would have selected for an efficient and fail-safe method for cancer suppression”, the researchers wrote in the study. Using more extensive data from an “Elephant Encyclopedia” that records the causes of death of captive elephants worldwide, Schiffman estimated that less than 5 per cent of elephants die of cancer, compared with 11 to 25 per cent of humans. Scientists found that elephants have a huge surplus of a major cancer-fighting gene – 20 copies versus one copy in humans. The second team found many other species have only one copy, just like humans. These bonus genes might enable elephants to weed out potentially cancerous cells before they can grow into tumors.
Schiffman’s team collaborated with Utah’s Hogle Zoo and Ringling Bros. “The next steps are to figure out precisely how these extra copies are working in the cell, and if there are other genes with elephant-specific changes evolved in their cancer resistance”.
Why elephants do not get cancer is a famous conundrum that was posed – in a different form – by epidemiologist Richard Peto of the University of Oxford, UK, in the 1970s.
Schiffman said, “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 fix itself”.
As expected, the people with Li-Fraumeni syndrome had the least cell death – just 2.7 percent of their blood cells died.
“As aging occurs, modern humans appear to be exceptionally vulnerable to cancer, especially in more developed societies”, they write.
The researchers then took elephant and human blood and exposed the samples to drugs and radiation that cause DNA damage, and watched how the samples reacted.
To test this, the researchers did a side-by-side comparison with cells isolated from elephants (n=8), healthy humans (n=10), and from patients with Li-Fraumeni Syndrome (n=10). The animals’ cells carry out a controlled self-destruction called apoptosis in response to DNA damage at much higher rates than do human cells. “Most cancers are preventable”, he said.
“We think that making more p53 is nature’s way of keeping this species alive”.
Feld Entertainment is dedicated to the preservation of Asian elephants and part of these efforts includes research.
Now scientists believe they know why.
“It is not immediately clear what lessons there are from this elephant tale for risk of cancer in humans”.
In the new study, Schiffman teamed up with Carlo Maley, an evolutionary cancer biologist at Arizona State University, Tempe, and colleagues.
Naked mole rats and elephants protect against cancer in different ways, Seluanov notes. Schiffman and his team, for example, plan to investigate natural or synthetic compounds that can mimic the amplification of the p53-associated gene seen in elephants.
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Schiffman and co-authors, Lisa Abegglen, Ashley Chan, Kristy Lee, Rosann Robinson, Michael Campbell, and Srividya Bhaskara are from Huntsman Cancer Institute and the University of Utah, Aleah Caulin and Shane Jensen are from the University of Pennsylvania, Wendy Kiso and Dennis Schmitt are from the Ringling Bros.
