Which Dogs Are More Prone to Cancer? And Other Questions

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An Asian elephant is seen in its enclosure at Pairi Daiza wildlife park, in Brugelette, Belgium on September 6. Drs. Joshua D. Schiffman and Matthew Breen are looking at animals like elephants and dogs to see what makes them susceptible or immune to cancer and how we can utilize that information for human diagnosis. Yves Herman/Reuters

Following our cover story on how cancer mortality in the animal kingdom is informing research, we asked readers to submit their questions for Dr. Joshua D. Schiffman and Dr. Matthew Breen though social media using the hashtag #CancerQs.

Both Schiffman and Breen are looking at animals like elephants and dogs to see what makes them susceptible or immune to cancer and how we can utilize that information for human diagnosis. Here are their responses to some of those questions.

Are there plans to study other pets exposed to the same living conditions as humans in the way Dr. Breen studies canine oncology? 

Dr. Breen: Our group, as well as others, are already studying cancers in other domestic species, including pets such as cats. In addition we have a very active program looking at cancer in wildlife. These exciting collaborations involve several institutions around the world and are combining to provide new information about the genetic and environmental factors that may be impacting cancers in numerous animal species, including humans.

Related: Why Elephants Don't Get Cancer—and What That Means for Humans

Dr. Schiffman: We look forward to working with Dr. Breen (and other collaborators) to use our knowledge of human cancer risk and tumor growth to compare to animal cancer as Dr. Breen has outlined.

Are larger dogs more prone to cancer? Are there certain breeds that are particularly prone? 

Dr. Breen: Cancer can affect any size or breed of dog, including mixed breeds. In fact almost half of all canine cancers are diagnosed in mixed breeds. However, among purebred dogs, some breeds are highly predisposed to certain types of cancer. To name a few, golden retrievers are predisposed to lymphoma and hemangiosarcoma, Bernese mountain dogs, flat coated retrievers and rottweilers are prone to histiocytic sarcoma, Scottish terriers, beagles, West Highland white terriers and Shetland sheepdogs are prone to bladder cancers, and boxers and Boston terriers are prone to some types of brain cancer.  The diligent work of the research community, collaborating with thousands of dog owners and their veterinarians, provides a solid foundation on which our cancer and comparative studies are based.

What's been the most frustrating part of your research?

Dr. Breen: The most frustrating aspect of our research has been an inability to make progress faster, so that we can offer more help to animal and human patients diagnosed with cancers. This limitation is solely due to a chronic lack of funding to support the field of comparative oncology.

Dr. Schiffman: One frustrating aspect of the elephant research has been the lack of elephant-specific reagents or tools for our experiments. We've had to get creative and search for reagents designed to be used on human cells that also work for elephant cells. Like Dr. Breen, our research also has been slowed by an initial lack of funding. The more people become aware of our comparative oncology research and want to be involved, we hope the faster our discoveries will come!

Related: That Bird Just Saved My Life: What Animals Can Teach Doctors

What has been the reception to your work in the broader oncology community? 

Dr. Breen: Among veterinary medical professionals the reception has been phenomenal. Among human medical professionals the reception has been somewhat less enthusiastic, but is changing. This change is coming about as we provide more education about new opportunities offered by a comparative approach. Our compelling data shows that consideration of cancers across species is accelerating important discoveries toward improved diagnosis and treatments for both animal and human patients.  

Dr. Schiffman: The initial response from oncology community has been skepticism. Because p53 is one of the most studied tumor suppressor genes, and people have been trying to find ways to increase p53 function for many years, they doubt that elephant retrogenes will lead to a future therapy. However, based on our findings published this week in JAMA, we remain convinced in the therapeutic potential of elephant p53. We are careful not to over-promise or claim that we have discovered a cure to cancer, or a way to prevent cancer. However, we do claim that elephants rarely develop cancer, have evolved extra copies of TP53, and that their cells respond more robustly to DNA damage compared to human cells or cells from patients with Li-Fraumeni Syndrome (who are prone to cancer). We will continue to explore the way these extra TP53 genes might be working in elephants to prevent cancer and then how to apply this to our human patients. We will work hard to prove the skeptics wrong.