Devil face tumor disease (DFTD), discovered in 1996, sounds like the worst affliction possible. Fortunately for humans, only Tasmanian devils can contract this form of cancer – which is only one of three known directly transmissible cancers. Unfortunately for them, their survival rate is essentially zero if they contract it.
Remarkably, a new Nature Communications study has revealed that they are now becoming resistant to this infectious face cancer. It seems the gears of evolution have been spinning just fast enough to turn the tide against DFTD, and this new devilish defense couldn’t have come at a better time – the tumor has wiped out 80 percent of wild devils in the last two decades alone.
“First and foremost, this gives us hope for the survival of the Tasmanian devil, which is predicted to be extinct but isn't,” study co-author Andrew Storfer, a professor of genomics at Washington State University, told a press conference. “We see that the devils apparently are evolving genes that may be associated with resistance to the disease.”
“We're talking about roughly six generations in some populations, which is a very short period of evolutionary time,” he added, highlighting just how quickly this new defense has appeared.
An international team looked at biological samples from 294 devils across three different areas of the Australian island, both before and after the disease appeared. Using a series of cutting-edge genetic sequencing methods, they were able to look for changes across the entire genome of the devils, with over 800,000 individual locations across the genome of each individual devil mapped out.
They discovered that two genetic segments were mutating faster than the rest of the genome in all three populations of wild devils. Significantly, seven genes within these segments were found to be connected to the immune system – and some were very similar to cancer-related genes found in our own species’ genetic sequence.
DFTD, in all its gory glory. AAP/Sarah Peck/PA
These potentially anti-cancer genes, which influence how the body sends immune cells to dysfunctional tissue growths or pathogens, are most likely the reason why the Tasmanian devil is beginning to fight back the DFTD plight. By harnessing this knowledge, researchers may be able to help keep these devils from falling into extinction.
In any case, one enormous mystery still remains. Namely – where did DFTD come from in the first place, and why is it so easily transmissible? Additionally, it’s not clear what DFTD and the other two directly transmissible cancers have in common.
One of the others jumps between the genitals of dogs when they mate. It’s an ancient cancer type, one that’s at least 11,000 years old. The other is spread between bivalves on the western coast of the US, and worryingly, this appears to be able to spread across different species. Hypothetically, this makes transmittable cancers a threat to all species, not just one.
Although a lot more work needs to be done, this latest study represents a remarkable breakthrough in our understanding of the evolution of the Tasmanian devil, the world’s largest carnivorous marsupial. With its muscular build, extremely disgusting scent, and it’s horrifying, ear-splittingly loud screech, it’s a globally-recognized animal.
In terms of land-based mammalian predators, its bite is actually one of the strongest in the world, and it is through this bite that DFTD is spread between sparring devils. The devil death spiral meant that the animal was considered “endangered” in 2008, and captive breeding programs hoping to foster a generation of DFTD-free devils have consequently been underway for some time now.
Devil combat. Susan Flashman/Shutterstock
[H/T: BBC News]