Although contagious cancers aren’t a huge concern in human health, they have been devastating to some animal species, including most recently Tasmanian devils and California sea lions. Now, scientists are launching studies that they hope will shed light on how these cancers form and spread. And they believe what they learn will advance the search for cures to human cancers, as well, by unlocking the mysteries of cancer evolution, remission and recurrence.
In late August, Washington State University biology professor Andrew Storfer published a paper in the journal Nature Communications describing how some species of Tasmanian devils are developing a genetic resistance to devil facial tumor disease (DFTD). The disease, first detected in 1996, is contagious and almost always fatal, and it has sparked concerns in Australia that Tasmanian devil colonies could be wiped out altogether. But 20% of animals in affected areas survive, raising questions about whether those devils have a different genetic makeup than those who succumb to DFTD.
Storfer teamed up with scientists from Great Britain and Australia to collect DNA from Tasmanian devils in three sites where DFTD was detected. They discovered 5 genes that are known to be related to cancer and immune functioning in other animals. They are now working on determining the exact function of those genes and are hoping to breed DFTD-free devils to see if they can increase the population of resistant animals.
"Our study suggests hope for the survival of the Tasmanian devil in the face of this devastating disease," Storfer said in a release about the study. "Ultimately, it may also help direct future research addressing important questions about the evolution of cancer transmissibility and what causes remission and reoccurrence in cancer and other diseases."
At the Marine Mammal Center in Sausalito, CA, scientists are searching for clues to another form of deadly, transmissible cancer that seems to be growing more prevalent in the state’s sea lions. The cancer is sparked by a virus and spreads in the reproductive organs of both males and females, according to BioGraphic, a publication of the California Academy of Sciences. It was first identified in 1978, but now 26% of sea lions examined after they die are found to have the cancer, up from 18% two decades ago.
The center’s scientists studied the DNA of cancerous tissues from sea lions and discovered a form of herpesvirus that wasn’t previously known, according to BioGraphic. They are now studying that virus more deeply to try to prove a link between it and the cancer. They also take extensive samples from the blood, skin and organs of animals that have succumbed to the disease and study them looking for further clues.
They’ve discovered that all of the sea lions with cancer carry the previously identified herpesvirus, and that they all have a common genotype that may contribute to the spread of the cancer. They also have pollutants in their blubber like PCBs and DDT, which are known to suppress immunity.
The link to environmental factors may be important to understanding how cancer evolves, not just in sea lions, but also in people, says Frances Gulland, senior scientist at the Marine Mammal Center. “These are contaminants the sea lions are acquiring from their prey,” Gulland told BioGraphic. “And the fish they eat are the same fish that we eat.”