Scientists at Cold Spring Harbor Laboratory have spent the past two years trying to understand a bizarre cancer cluster among Tasmanian devils on their namesake island off the coast of Australia, even as the devils were dying at an alarming rate.

Now the team of researchers reports not only several key findings in the cancer mystery, they also know why the animals are able to infect each other with an aggressive form of cancer that distorts their faces and snuffs out their lives. Deadly cancer cells were transmitted devil-to-devil whenever they bit each other or fought, causing a condition scientists call devil facial tumor disease.

Cancer, in humans, is not generally considered a disease that can be transmitted as a result of exposure to a malignant cell. But the mechanism, in the devils, is different.

Because the cells themselves - and not a virus or other infectious agent - are causing the disease in devils, the discovery raises new questions about how cancer cells work and transmit the disease, said Gregory Hannon, a professor at the laboratory and an expert in cancer genetics.

"It has been quite a long road but we've been able to make some headway," said Hannon. He said Cold Spring Harbor scientists discovered the cancer is emanating in nerve cells, or more specifically, according to Gannon, in Schwann cells, which make up the insulating tissue that encases and protects nerves.

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In humans, cervical cancer and certain liver malignancies are considered transmissible because viruses passed from one person to another corrupt the DNA of healthy cells.

There have been extremely rare reports of brain cancers developing in recipients of transplanted livers when donors of the organs had brain tumors undetected before the transplant. Only a handful of those cases have been reported. Generally, humans and other mammals reject foreign tissue.

But in the devils, Gannon said, their isolation has resulted in animals that are virtually identical genetically, all having descended from a few "founding devils." As a result, they don't reject cells from each other, a situation that theoretically, he said, can easily allow cancer cells to seed themselves in affected devils.

"This is a very interesting case involving a cancer that is moving throughout a population," he said. "One of the next steps is to understand if there is anything special about this particular cancer that makes it so aggressively metastatic."

Working with Dr. Elizabeth Murchison, a Cold Spring Harbor molecular geneticist from Tasmania, and colleagues at the lab and in Tasmania, the research is the first to unravel how cancer can be transmitted in a bite. The study is reported in today's journal Science.