Dr. Schiffman and his colleagues found in their research that elephants have a remarkably low rate of cancer. They reviewed zoo records on the deaths of 644 elephants and found that less than 5 percent died of cancer. By contrast, 11 percent to 25 percent of humans die of cancer — despite the fact that elephants can weigh a hundred times as much as we do.
To understand the elephants’ defenses, the scientists investigated a gene that is crucial for preventing cancer, called p53. The protein encoded by the gene monitors cells for damage to the DNA they contain. In some cases, it triggers the cells to repair the genes. In other cases, p53 stops cells from dividing further. And in still other cases, it even causes the cells to commit suicide.
One sign of how important p53 is for fighting cancer is what happens to people born with a defective copy of the gene. This condition, known as Li-Fraumeni syndrome, creates a lifetime risk of cancer of more than 90 percent. Many people with Li-Fraumeni syndrome get cancers as children and can have several types of cancer over their lifetimes.
Dr. Schiffman and his colleagues found that elephants have evolved new copies of the p53 gene. While humans have only one pair of p53 genes, the scientists identified 20 pairs in elephants.
Dr. Lynch and his colleagues also found these extra genes. To trace their evolution, the researchers made a large-scale comparison of elephants to other mammal species — including extinct relatives like woolly mammoths and mastodons whose DNA remains in their fossils.
The small ancestors of elephants, Dr. Lynch and his colleagues found, had only one pair of functional p53, like other mammals. But as they evolved to bigger sizes, they steadily evolved extra copies of p53.
“Whatever’s going on is special to the elephant lineage,” Dr. Lynch said.
- Carl Zimmer
To understand the elephants’ defenses, the scientists investigated a gene that is crucial for preventing cancer, called p53. The protein encoded by the gene monitors cells for damage to the DNA they contain. In some cases, it triggers the cells to repair the genes. In other cases, p53 stops cells from dividing further. And in still other cases, it even causes the cells to commit suicide.
One sign of how important p53 is for fighting cancer is what happens to people born with a defective copy of the gene. This condition, known as Li-Fraumeni syndrome, creates a lifetime risk of cancer of more than 90 percent. Many people with Li-Fraumeni syndrome get cancers as children and can have several types of cancer over their lifetimes.
Dr. Schiffman and his colleagues found that elephants have evolved new copies of the p53 gene. While humans have only one pair of p53 genes, the scientists identified 20 pairs in elephants.
Dr. Lynch and his colleagues also found these extra genes. To trace their evolution, the researchers made a large-scale comparison of elephants to other mammal species — including extinct relatives like woolly mammoths and mastodons whose DNA remains in their fossils.
The small ancestors of elephants, Dr. Lynch and his colleagues found, had only one pair of functional p53, like other mammals. But as they evolved to bigger sizes, they steadily evolved extra copies of p53.
“Whatever’s going on is special to the elephant lineage,” Dr. Lynch said.
- Carl Zimmer
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