Second form of contagious cancer found in Tasmanian devils

Researchers say it raises questions about the current level of understanding when it comes to cancers that can spread between individuals.

This new discovery was published in the Proceedings of the National Academy of Science journal in December after it was detected in eight devils in southeast Tasmania. The team were studying facial tumors on a Tasmanian devil found in south-eastern Tasmania in 2014 when they discovered the cancer was transmittable, but not the same type that had been previously found. They have since detected that cancer type in eight individuals.

The discovery of a second transmissible cancer in Tasmanian devils changes our perception of the potential of cancer cells to adapt to new niches as parasitic clonal cell lineages. Now another “contagious” cancer has been found.

This has led to much of the Tasmanian devil population being affected, with many usually dying within months of contracting cancer.

Transmissible cancers – cancers which can spread between individuals by the transfer of living cancer cells – are believed to arise extremely rarely in nature.

Ask The Big Question: Could humans be at risk from the new contagious cancer?

Scientists are now anxious that other, as-yet-udiscovered transmissible cancers may exist in this species. And the most notable type of contagious cancer occurs in the world’s largest carnivorous marsupial: the Tasmanian devil. As they mate and feed, they frequently bite each other, making it easy for the cancer to spread. As this cancer has spread throughout the island, populations of the marsupials have declined to the point that they were listed as endangered in 2008 by the International Union for Conservation of Nature.

To date, only three forms of transmissible cancer have been observed in nature – in dogs, soft-shell clams and in Tasmanian devils. With a second type of cancer potentially spreading across Tasmania as well, the devils face more potential disease as they struggle to survive.

Unfortunately for the Tasmanian devils, lightning has apparently struck twice, as scientists from Cambridge and the University of Tasmania has identified a second type of contagious cancer that is genetically distinct but visibly indistinguishable from the previously discovered form. The discovery was made a year ago when a devil was found with tumours in the southeastern part of the island.

“Transmissible cancers are extremely rare, but for two [to occur] in the one species, astonishing”, said study co-author Gregory Woods, an immunologist at the University of Tasmania. In addition, such cancers might appear more frequently in these small carnivores. Regardless of whether the plight of Tasmanian devils represents the existence of a common pathological process that has previously been overlooked, is the effect of an unfortunate species-specific vulnerability, or has arisen due to an exceptionally improbable concomitance of events, clarification of the biological basis of DFT2 promises to illuminate important concepts underpinning cancer evolution.