A mysterious and deadly cancer that has been plaguing populations of Tasmanian devils for more than a decade must have abandoned its original host long ago, essentially becoming a parasite of the devils, researchers say.
Tasmanian devil | Image courtesy of A/Prof Geoff Shaw, Department of Zoology, University of Melbourne
By performing a large-scale genetic analysis of this disease, the same researchers have identified genes that are involved with the cancer’s transmission and mode of action—along with a particular protein that might be used to help diagnose the disease in the future.
Tasmanian devils are the largest marsupial carnivores on the planet today, but experts warn that, without intervention, this deadly cancer could potentially wipe out all wild Tasmanian devils within the next 50 years.
Devil facial tumor disease, or DFTD, is the rapidly fatal, transmissible cancer that was first observed in 1996. Since then, it has been implicated in the declining populations of devils across the country of Tasmania. The disease is characterized by large tumors on the face and mouth, which frequently metastasize to internal organs.
To investigate the origin of DFTD, Elizabeth Murchison from the Cancer Genome Project in England, along with colleagues from across the world, explored the genetic evolution of these lethal Tasmanian tumors. Their results are published in the 1 January 2010 issue of Science.
Tasmanian devil facial tumor disease | Image courtesy of Save the Tasmanian Devil Program
The researchers were able to confirm that the cancer was passed from one Tasmanian devil to another by physical contact—and that it has originated from Schwann cells, which participate in nerve repair after injury and modulate immune reactions in the peripheral nervous system.
“Studies of captive Tasmanian devils have suggested that the species is prone to developing tumors, particularly carcinomas,” Murchison writes in her report. “However, DFTD does not resemble previously described devil cancers, and determining its etiology is critical for developing management strategies for the disease.”
Murchison and her colleagues sampled 25 different devil tumors from all over Tasmania, and found that they were all genetically distinct from their hosts—but essentially identical to one another. The researchers also identified a particular protein, known as periaxin, which is expressed Schwann cells and present in every tumor. They say that periaxin could be used to diagnose the disease, and in the future, it might be exploited to find a cure to DFTD.
Murchison, who grew up in Tasmania, writes in the report: “There are no diagnostic tests, treatments, or vaccines available for DFTD… [But] our catalog of genes provides a framework for this work.”
Their results are timely because the number of Tasmanian devils in the wild has dropped by about 60% in the last decade as a direct result of the disease.