A new study suggests a possible reason why: Elephants have 20 times as many copies of a key cancer-fighting gene as humans.
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The myth that sharks don’t get cancer has encouraged people to kill them and sell their cartilage for nutritional supplements. “If you kill the damaged cell, it’s gone, and it can’t turn into cancer”. It detects stress or damage in the cell, and stops the cell from dividing until the stress has passed or the DNA is repaired.
Recently a team of geneticists led by Joshua Schiffman at the University of Utah made major headway in this direction when they studied the cells of Asian and African elephants from the San Diego Frozen Zoo and found that elephants’ genomes possessed 20 copies of a tumor suppressing gene called P53.
Study discovered that most cancers costs in elephants are below in human population. And TP53, as Schiffman and other scientists describe it, is the so-called “Guardian of the Genome”.
Huntsman Cancer Institute researchers performed the study in conjunction with a team from Ringling Bros.
But scientists have cautioned that more research would be needed to fully understand the mechanisms in play in elephants.
Dr Schiffman added: “Nature has already figured out how to prevent cancer”. The researchers compared the radiated cells from elephants, healthy humans and people with Li-Fraumeni Syndrome and found that elephant cells self-destruct at double the rate of human cells and five times the rate of Li-Fraumeni cells.
Next, the scientists investigated how the TP53 gene protected against cancer. “We don’t know what the tradeoff was, [but] elephants either found a way to deal with it or broke whatever constraint prevented organisms from evolving many P53 copies”. The extra copies probably accumulated millions of years ago as the gene was accidentally duplicated many times in the ancestors of elephants, the researchers suggest.
Laboratory tests showed how the gene led elephant white blood cells whose DNA had been damaged to commit suicide.
“We are now exploring how to apply these discoveries to children and families most at risk to develop cancer”, Schiffman said in a release.
He believes that further research on elephants, and other animals that tend to ward off cancer, “may indeed provide a few clues as to how we might better harness p53-regulated cellular pathways in humans”.
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.
One species that’s been hit particularly hard by cancer in recent years is the Tasmanian devil, a species at risk of becoming extinct over the next decade because of lethal cancers spread by a parasite.
According to the results of a new study in the Journal of the American Medical Association (JAMA), 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. People with this syndrome are 90 percent more likely to develop cancer compared to those who don’t.
Naked mole rats and elephants protect against cancer in different ways, Seluanov notes. “We expected to see that elephants were repairing DNA like nobody’s business”, Schiffman says. “The explanation for this dilemma may involve other factors that greatly increase cancer risk”. Peto noted that, in general, there is little relationship between cancer rates and the body size or age of animals.
“And when we zapped their blood with radiation in the laboratory”, Schiffman said, “their cells didn’t seem to die at all”.
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“These findings, if replicated, could represent an evolutionary-based approach for understanding mechanisms related to cancer suppression”, the study authors wrote.
