What can Tasmanian devils teach us about cancer?

Something extraordinary is evolving among the feisty inhabitants of the remote north-west coast of Tasmania. Something that’s both astounding and delighting the researchers monitoring them.

For more than 20 years, these apple-isle locals have been suffering an ugly cancer that’s caused population numbers to rapidly decline, Devil Facial Tumour Disease (DFTD). The problem has raised many complex questions and stirred urgent conservation efforts among research institutions around the world. But now, in an unprecedented and ground-breaking discovery, an isolated colony of Tasmanian devils appear to be saving themselves from extinction.

Having immersed herself and her research in the devil’s world for a number of years, Dr Beata Ujvari, an evolutionary ecologist and Senior Lecturer in Bioinformatics and Genetics at Deakin University, is excited by the new findings. ‘Encouragingly, the results suggest the devils may be able to overcome the extinction threat of the disease that has devastated the population for over two decades.’

Luck of the devil: discovering the problem

Once considered a nuisance by early European settlers in Hobart, the Tasmanian devil steadfastly rose to become an internationally-renowned icon for the small Australian island it exclusively inhabits.

How fortuitous it turned out to be when, in 1996, Dutch wildlife photographer Christo Baars made his way to the tiny isle and photographed several devils with grotesquely disfigured faces. Intrigued, he showed his photos to a local zoologist, who was both baffled and disturbed by what he saw.

Slowly, word of the grisly discovery spread. Five years later, biologists found more disfigured devils on the eastern coast of Tasmania. This time, the alarm was officially raised – something peculiar was fast forming among the protected species. In 2006, a decade on from Baars’ accidental discovery, the devil’s plight was formally recognised and named as Devil Facial Tumour Disease (DFTD).

With the environmental spotlight now firmly on the devil, it became apparent the disease had caused significant population declines – as great as 95 percent by 2016 in some areas. In 2008, the species was formally upgraded to ‘Endangered’ on the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List – widely considered to be the most authoritative system for classifying risk of species extinction.

Better the devil you know: understanding the cancer

A formidable creature, the Tassie Devil can consume nearly half its own body weight in just 30 minutes. But its fierce appetite and highly-tuned survival instincts have proven no match for the deadly DFTD. ‘Quite the contrary, unfortunately,’ says Dr Ujvari. ‘As soon as they become sexually mature at two years of age, devils start fighting amongst themselves for food and for mates, which ultimately spreads the disease. The devils then die of starvation or organ failure, usually within six months after the first lesions appear.’

Like many human cancers, DFTD is swift, elusive and unrelenting. ‘It’s transmitted as an allograft, meaning that the actual cancer cells are the infectious agents that are being passed between the devils,’ Dr Ujvari explains.

‘Under natural circumstances, the devil’s immune system should recognise the foreign or infectious cells and fight them. But in the case of DFTD the cancer cells are capable of avoiding immune recognition and are therefore able to infect the host.’ In other words, the disease is so sophisticated that it essentially hides from the devil’s immune system and freely attacks under disguise.

The devil is in the detail: the surprising resistance

Two decades on from those infamous photos, another surprising discovery has been made. New research in 2016 uncovered that some populations of devils, where DFTD has been present for more than 20 years, have started showing signs of resistance to the disease.

One particular population in the north-west of Tasmania that was predicted to be extinct by now, in fact, still remains. Observation of this group over 10 years has revealed that DFTD infiltrated the colony in 2006 but failed to take hold to such extent as in other populations. Most importantly, on some devils the facial lesions appeared but did not grow and eventually regressed.

So what’s so special about this group? Up until now, it’s undoubtedly been the conservation efforts of many dedicated researchers that has stemmed the devils’ steady decline and turned their precarious situation around.

But now, the evidence suggests they’re rapidly evolving to develop a resistance to DFTD. Does this mean they can save themselves, and ultimately the species, from extinction?

Give the devil his due: sharing the knowledge

With this new research comes new hope, and a much bigger question: does this signal vital clues for the potential treatment or cure of some human cancers?

‘It could actually work both ways,’ Dr Ujvari suggests. ‘The mechanisms used by DFTD to evade the immune system are actually very similar to those observed and frequently employed by tumour cells in humans.’

‘If we can better understand the mechanisms of immune response modulation by both human and transmissible cancers, this could benefit oncologists developing treatment strategies for human cancers, as well as conservation biologists who are developing preventative and treatment measures to save the iconic devils from extinction,’ she concludes.

Interested in the complex world of animal biology? Check out Deakin’s wildlife and conservation biology courses.