DNA lets sharks take a bite out of cancer

A new study of shark DNA shows unique evolutionary changes in immunity genes may explain how sharks’ open wounds heal so fast and why the ocean’s top predator rarely gets cancer.

Research scientists at Nova Southeastern University and Cornell University probed the genetics of great white and great hammerhead sharks to learn why shark wounds heal rapidly and why sharks are so resistant to cancer.

Immune systems, fine- tuned over 400 million years of evolution, heal open wounds on sharks and rays within hours. Scientists suspect this amazing ability also may help sharks and rays fend off cancer.

The study, recently published in the journal BMC Ge

nomics, provides the first evidence that some shark and ray immunity genes have undergone evolutionary changes possibly tied to these novel immune system abilities, the researchers said.

“The immune system of sharks and rays has been battle- tested and evolved over hundreds of millions of years,” said Mahmood Shivji, director of NSU’s Save Our Seas Shark Research Center and Guy Harvey Research Institute in Fort Lauderdale.

Two shark genes especially stood out, the researchers said. Both genes have counterparts in humans, where their overexpression is linked with cancers. But in sharks, natural selection has modified the two genes into tumor preventives.

One gene codes for a protein that in humans helps inhibit an essential natural process called “programmed cell death.”

“At certain times, some cells have to stop dividing and die. That’s a good thing,” Shivji said. But overexpression of the gene inhibits normal programmed cell death, setting the stage for cancer. Research has shown that compounds from shark tissues can inhibit growth of new blood vessels on tumors.

“Several studies have demonstrated anti- tumor properties of shark- derived compounds in lab studies, said Shivji, who co- led this research with Michael Stanhope, a Cornell scientist. “It’s intriguing that we are now seeing evidence of evolutionary adaptation in these specific shark immunity genes, which just happen also to be involved in promoting cancer in humans.”

ANDREW BRANDY CASAGRANDE, AP A new study examining the genetics of sharks, including the great white shark, may help scientists understand what makes these ocean predators resistant to cancer.