A new study of shark DNA, including from the Great White Shark and Hammerhead Sharks, has revealed unique evolutionary changes in immunity genes that may explain how sharks’ open wounds heal so fast and why they rarely get cancer.

Sharks’ and rays’ immune systems are well known to be highly efficient: they heal open wounds in hours and are suspected to show a greater resistance to cancers. A recent study – funded primarily by Save Our Seas Foundation – provides the first evidence that some shark and ray immunity genes have undergone evolutionary changes possibly tied to these immune system abilities.

“The immune system of sharks and rays has been battle-tested and evolved over hundreds of millions of years,” said Mahmood Shivji, director of Nova Southwestern University’s Save Our Seas Shark Research Center and Guy Harvey Research Institute, who co-authored the study.

The researchers found that two shark immune genes especially stood out. Both genes have counterparts in humans, where their overexpression is linked with cancers. But the research shows that these genes in sharks have been modified by natural selection to be tumor preventatives.

One gene codes for a protein that in humans helps inhibit an essential natural process called “programmed cell death” – when some cells stop dividing and die. This is a good thing, Shivji explained, but overexpression of the gene inhibits normal programmed cell death, increasing the potential for cancer.

Research has shown that compounds from shark tissues can prevent growth of new blood vessels on tumours. However, according to Shivji, we are now seeing evidence of evolutionary adaptation in these specific shark immunity genes that are involved in promoting cancer in humans.

“Using genomics approaches to understanding [sharks’] immunity genesis is likely to produce many more exciting discoveries, some of which could potentially translate into human medical benefit,” Shivji said.

You can find the study published in the journal BMC Genomics.

Now we have another important reason to make sure we don’t lose these marvellous and ecologically critical animals to overfishing, as is currently occurring in many parts of the world. We’ve just scratched the surface in terms of learning what these ancient animals can teach us, as well as possibly provide us in terms of direct biomedical benefits.”

– Mahmood Shivji, director of Nova Southwestern University’s Save Our Seas Shark Research Center and Guy Harvey Research Institute

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