Tasmanian devils have had the outrageously bad fortune to be plagued by not just one, but two contagious cancers. But the ferocious Australian animals might finally be catching a break. Tasmanian devils may be evolving to resist devil facial tumor disease, which has wiped out nearly 80 percent of their population over the past 20 years. Areas of the animals’ genomes bearing a handful of genes involved in cancer and the immune system have changed distinctively in response to the deadly cancer, indicates a study published today in Nature Communications.
“This gives us hope for the survival of the Tasmanian devil,” coauthor Andrew Storfer, of Washington State University in Pullman, said in a press briefing on Friday.
Scientists ID’d the cancer in 1996, after they started noticing Tasmanian devils with tumors on their faces. Since then devil facial tumor disease, which is nearly always fatal, has spread throughout the animals’ range. The cancer is passed on when devils bite each other (which these aggressive predators do constantly). “This disease…moves from host to host, it’s effectively like one very long lived human tumor,” Storfer said.
And yet, despite epidemiological models predicting their extinction, long-diseased devil communities are still hanging on. To figure out why, Storfer and his colleagues turned to tissue samples that had been collected from Tasmanian devils in different areas both before and after the disease hit. The team scanned the animals’ genomes at more than 800,000 sites, looking for changes over time.
They found two small regions that differed before and after the advent of devil facial tumor disease in all three of the populations they’d sampled. Five of the seven genes found in these snippets of the genome are related to immune function or cancer risk in humans. Several of these are involved in directing immune cells to dysfunctional cells or pathogens, coauthor Brendan Epstein, of Washington State University, said during the press briefing.
The findings indicate that Tasmanian devils are evolving extremely quickly—over just a few generations. “The functions of these genes suggest that the devil immune system may be adapting to be able to recognize tumor cells,” the researchers wrote. They plan to verify what role these genes play in future studies.
It’s not clear if this evolution might also help Tasmanian devils withstand the second type of contagious facial tumors they are susceptible to. Tumors that can be passed between hosts are exceedingly rare, and the only other known cases have been seen in dogs and certain shellfish. The devils’ response might give scientists some insights about how cancers evolve to become transmissible.