Scientists have taken a major step toward understanding cancer in cats, opening what researchers once described as a genetic “black box.”
In a large international study published in Science, researchers genetically analyzed cat cancers on a scale that had not been attempted before. The work could improve cancer care for cats while also helping scientists better understand how some cancers develop in humans and other animals.
The researchers also created a freely available resource that other scientists can use to study the genetics of feline cancer.
Cancer is one of the leading causes of illness and death in cats, yet scientists have historically known far less about the genetic changes behind feline tumors than they do about cancers in humans or dogs.
Dr. Geoffrey Wood, a University of Guelph pathobiology professor and co-senior author of the study, said that gap has now begun to close.
“Despite domestic cats being common pets, there was very little known about the genetics of cancer in these animals,” Wood says, “until now.”
Cat and Human Cancers Share Key Genetic Changes
Researchers examined tumor samples from almost 500 domestic cats in five countries, searching for mutations and other genetic changes that help cancers form and grow.
Many cancers are driven by changes in certain genes that normally help control how cells grow, divide, repair damage, or die. When these genes are altered, cells can begin multiplying uncontrollably. Scientists often refer to genes that contribute directly to tumor growth as cancer driver genes.
The team found that many of the driver genes involved in cat cancers were also familiar from human and dog cancers.
One of the clearest examples appeared in aggressive mammary cancers, which arise in breast tissue.
The most common driver gene found in cat mammary tumors was FBXW7. More than 50 percent of the tumors examined carried a mutation in this gene.
FBXW7 normally helps regulate proteins involved in cell growth and division. When the gene is damaged, some of those growth promoting proteins can accumulate, potentially helping cancer cells survive and spread.
In humans, mutations in the FBXW7 gene in breast cancer are associated with worse prognosis – paralleling the change seen in cats.
Researchers also identified similarities between cat and human cancers affecting the blood, bones, lungs, skin, gastrointestinal system and central nervous system.
Shared Environments May Offer Cancer Clues
The similarities may be especially useful because domestic cats often live in the same environments as people.
Cats can encounter some of the same environmental factors as their owners, including household chemicals, air pollutants, smoke and other exposures that may influence cancer risk. Studying naturally occurring cancer in pets could therefore help researchers investigate how genetics and the surrounding environment interact.
“This study can help us understand more about why cancer develops in cats and humans, how the world around us influences cancer risk, and possibly find new ways to prevent and treat it,” says Wood.
The genetic findings could also have implications for treatment.
Researchers found that certain chemotherapy drugs were more effective against cat mammary tumors carrying the mutated FBXW7 gene.
The result was observed only in tissue samples, so it does not yet show that the same approach will work in living cats or people. Still, the finding suggests that genetic information could eventually help doctors and veterinarians identify treatments that work better for particular tumors.
This type of approach is known as precision oncology. Instead of treating every cancer of the same general type in exactly the same way, precision oncology uses the molecular and genetic features of an individual tumor to help guide therapy.
“Having access to such a large set of donated tissues allowed us to assess drug responses across tumor types,” says Dr. Sven Rottenberg, co-senior author at the University of Bern, “in a way that hasn’t been possible at this scale before.”
Bailey Francis, co-first author at the Wellcome Sanger Institute, said the findings could also have implications for dogs.
“When knowledge and data flows between different disciplines, we can all benefit.”
Using Cat Cancer Research to Help Pets and People
The project brought together researchers from the Wellcome Sanger Institute, U of G’s Ontario Veterinary College, the University of Bern and other institutions.
Rather than collecting all new samples, the team sequenced DNA from tissues that veterinarians had already obtained for diagnostic purposes.
That allowed scientists to study naturally occurring cancers from a large number of cats and compare the genetic patterns among different tumor types.
The findings also support a broader research strategy known as One Medicine.
The One Medicine approach emphasizes that human and veterinary medicine can inform one another. Cancer treatments developed for humans could potentially be evaluated in cats with naturally occurring tumors, while discoveries made during feline cancer studies and clinical trials could provide clues that help shape future human research.
That two way exchange is especially valuable because pets naturally develop many of the same diseases as people while sharing many aspects of the same environment.
Researchers hope the new genetic database will ultimately help bring more personalized cancer care to cats.
Dr. Louise Van Der Weyden, senior author at the Wellcome Sanger Institute, said the study provides a foundation for the next stage of feline cancer research.
“We can now begin to take the next steps forwards towards precision feline oncology, to catch up with the diagnostic and therapeutic options that are available for dogs with cancer, and ultimately one day, humans.”
The research was funded in part by EveryCat Health Foundation, the CVS Group, Wellcome, the Natural Sciences and Engineering Research Council of Canada and the Swiss National Science Foundation.
