This is a mystery that has stumped scientists all over the world. But a group of researchers at Huntsman Cancer Institute (HCI) at the University of Utah and Arizona State University have found the answer that could hold clues to fight against cancer.
The Scientists have discovered that 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, according to a study published on 9th October, 2015 in the Journal of the American Medical Association (JAMA.
The study determined over the course of several years further reveals that elephants have a more robust 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, and five times that of cells from patients with Li-Fraumeni Syndrome, who have only one working copy of p53 and more than a 90 percent lifetime cancer risk in children and adults” according to the researchers.
The results also suggest that extra p53, a protein well known for its cancer-inhibiting properties could explain elephants’ enhanced resistance to cancer.
“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,” says co-senior author Joshua Schiffman, M.D., pediatric oncologist at Huntsman Cancer Institute, University of Utah School of Medicine.
According to Schiffman, elephants have long been considered a walking conundrum. Because they have 100 times as many cells as people, they should be 100 times more likely to have a cell slip into a cancerous state and trigger the disease over their long life span of 50 to 70 years. And yet it’s believed that elephants get cancer less often, a theory confirmed in this study.
Analysis of a large database of elephant deaths estimates a cancer mortality rate of less than 5 percent compared to 11 to 25 percent in people.
“It’s as if the elephants said, ‘It’s so important that we don’t get cancer, we’re going to kill this cell and start over fresh,’” says Schiffman. “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.”
With respect to cancer, patients with inherited Li-Fraumeni Syndrome are nearly the opposite of elephants. They have just one active copy of p53 and more than a 90 percent lifetime risk for cancer.
“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,” says Schiffman. “We think that making more p53 is nature’s way of keeping this species alive.”
Additional studies will be needed to determine whether p53 directly protects elephants from cancer.
p53 is an ancient gene found in all multicellular animals. It detects stress or damage in the cell, and stops the cell from dividing until the stress has passed or the DNA is repaired. Humans inherit one copy from each parent, and it has a crucial role in protecting us from cancer, according to a New Scientist publication.
The elephant story represents one way that evolution may have overcome cancer. Other evidence suggests that naked mole rats and bowhead whales have evolved different approaches to the problem.