How transmissible cancer in Tasmanian devils depends on host genetics

Cancer usually dies with the organism in which it first developed. But transmissible cancer in Tasmanian devils breaks that rule. Its cells can move between animals, establish new tumours and continue surviving long after the original host has died.

This extraordinary disease raises an equally intriguing question: why are some devils more susceptible than others? Does the outcome depend mainly on the animal's own genetics, on the tumour's genome, or on interactions between genetic variants?

A study published on October 30, 2026, in the Journal of Evolutionary Biology offers new evidence. By examining 312 matched pairs of Tasmanian devil and tumour genomes, researchers identified dozens of candidate genetic variants associated with interactions that may influence susceptibility to infection.

The findings suggest that understanding this cancer requires looking beyond individual genes.

A cancer that outlived its original host

Tasmanian devils are carnivorous marsupials native to the Australian island of Tasmania. Their powerful jaws and aggressive encounters are central to the story of one of the most unusual infectious diseases known.

During fights over food or mating, devils frequently bite one another. Those bites can transfer living cancer cells directly into another animal's tissues.

Unlike a conventional infection, the infectious agent is not a bacterium or a virus. It is the malignant cell itself.

Once transferred, those cells can establish a new tumour. In biological terms, the disease behaves like a naturally occurring transplantation of cancerous tissue.

The first recognised transmissible devil cancer, known as DFT1, was observed in 1996. It subsequently spread across much of Tasmania and contributed to major population declines.

A second independently originating cancer, DFT2, was discovered later. Both can spread through biting, but they are distinct tumour lineages.

The new study focuses on DFT1.

Its success is surprising because foreign cells should normally be rejected by the immune system. Organ transplantation between genetically different individuals often requires immunosuppressive drugs precisely because the recipient recognises the donor's cells as foreign.

DFT1 has evolved ways to escape that recognition. One mechanism involves reducing the expression of molecules that normally help immune cells distinguish the body's own tissues from foreign tissue.

This explains part of the cancer's remarkable ability to spread. It does not fully explain why individual devils differ in susceptibility.

Why genetic combinations may matter

The research team, led by Enrique Celemín at the University of South Florida, analysed 312 matched devil–tumour genome pairs.

Their focus was epistasis, a genetic phenomenon in which the effect of one variant depends on the presence of other variants.

A DNA change might have little detectable effect on its own, for example, yet influence a biological trait when combined with a particular variant elsewhere in the genome.

Studies that examine genetic variants one at a time can therefore miss part of the biological picture.

Using statistical tests designed to detect evidence of these interactions, the researchers identified 50 candidate single-nucleotide polymorphisms, or SNPs, in the devil genomes.

These variants were associated with epistatic effects relevant to susceptibility to DFT1.

Importantly, the findings do not establish 50 genes that protect against cancer. They identify candidate statistical signals whose biological effects have not been directly demonstrated.

Several functional categories stood out.

One involved glutathione transferase activity. These enzymes participate in cellular responses to potentially damaging chemical compounds and oxidative stress.

Another involved ATP synthesis, the process through which cells generate a major source of usable energy. This points towards possible contributions from cellular metabolism.

The third category was less expected: sensory perception of chemical stimuli.

The authors suggest that smell-related biology might influence how devils encounter infected animals, potentially through behavioural avoidance.

This is an interesting possibility rather than a demonstrated mechanism. The study did not test whether animals carrying particular variants can recognise infected companions by smell or avoid risky encounters more effectively.

The tumour genome produced a different result

The researchers also examined genetic interactions within DFT1 tumour genomes.

Here, they detected only two statistically significant SNPs, compared with the 50 candidate variants identified in the hosts.

That difference may suggest a smaller detectable contribution from epistatic interactions to tumour transmissibility than to host susceptibility.

It would be misleading, however, to interpret the counts as showing that host genetics is 25 times more important than tumour genetics.

The number of detectable associations depends on genetic variation, statistical power and the analytical methods used. A difference in the number of signals does not directly measure the biological importance of each genome.

There is another important distinction: identifying a genetic association does not establish the molecular mechanism behind it.

The findings do not experimentally demonstrate that any particular combination of variants changes tumour growth, immune recognition or transmission.

They do, however, extend earlier evidence that Tasmanian devils and their transmissible cancer are involved in an ongoing evolutionary relationship.

Previous research has suggested that the interaction between host and tumour genomes can help explain variation in infection dynamics. The new study adds another layer by examining interactions among genetic variants.

That matters because transmissible cancers occupy a unique position in evolutionary biology.

Most cancers evolve inside a single organism. Their fate is closely tied to the survival of that individual.

DFT1 follows a different evolutionary path. Its cells move between hosts, carrying a tumour genome with its own history of mutations and selection.

Each infected devil contributes another genetically distinct environment in which the tumour must survive.

The outcome may therefore depend on combinations of genetic factors that cannot be understood by examining individual variants in isolation.

Tasmanian devils and DFT1 are participating in an unusual evolutionary process: the animal population is changing under pressure from a transmissible cancer, while the cancer itself continues to evolve as it moves between animals.