Australasian Science: Australia's authority on science since 1938

Devil Tumour Changing

By Stephen Luntz

The cancer that is killing Tasmanian devils is changing.

Little is known about the effects of the changes, but there is hope they may be used to fight the disease and possibly offer insights into human cancers.

In Proceedings of the Royal Society B, A/Prof Kathy Belov and Dr Beata Ujvari of the University of Sydney’s Faculty of Veterinary Science have revealed that samples of the tumour from 5 years ago and today show alterations in the methylation tags of certain genes, an important factor in epigenetics.

“Epigenetic changes can result in differences in how a gene is expressed without altering the DNA sequence. We found that in devil tumours these tags have been removed over time. There were more tags 5 years ago than there are now. This suggests that more genes have been switched off in today’s tumours than those in the past,” Belov says.

Epigenetic changes can cause a tumour to become more aggressive or slow its development, but Ujvari says it is not yet clear in which direction the changes are going. “It is known that in human cancers methylation changes as they adapt to their environment,” Ujvari says.

Besides devil facial tumour disease (DFTD), the one transmissible cancer known is found in dogs. It is believed this was once lethal but evolved to become benign, giving hosts a greater chance to transmit the tumour. Ujvari expects that with time the same thing would happen to DFTD, but adds: “There are millions of dogs in the world. We don’t have enough devils left for this to happen.”

The prospects for a vaccine against DFTD have been thought poor because the genome is so similar to that of the devils themselves that any immune response would trigger autoimmune effects. However, Ujvari says that “it might be possible to develop an epigenetic marker specific to the tumour, allowing the immune response to not affect other tissues.”

Epigenetic reversal has been used in the treatment of some human cancers, avoiding the side-effects of chemotherapy, and such an approach may prove practical for DFTD once it is known which changes make the disease more and less aggressive.

DFTD’s unusual nature makes it a powerful research tool. By responding to varying environments in different hosts it may offer insight into how other cancers respond to incomplete chemotherapy.