From Our 2015 Archives
What Dogs Are Teaching Us About Cancer
By R. Scott Rappold
Reviewed by Arefa Cassoobhoy, MD, MPH
Oct. 29, 2015 -- When Marisa Rockwell took her dog Valo to the veterinarian for trouble peeing, she suspected some sort of urinary tract infection.
The diagnosis was much worse: bladder cancer, two different types. The pit bull mix was given 9 months to live -- a devastating prognosis for Rockwell, his owner for a decade. So when she heard about an experimental study on canine cancer at a nearby clinic, she signed up.
"I said, 'If there's no cure for either of these cancers already, we might as well try something that's not been tried before,'" says Rockwell, of Guilford, CT. Valo received two shots and follow-up testing, but that was it. He continued to live at home.
More importantly, Valo continued to live. Ten months after the diagnosis, Rockwell says he is showing no signs of illness.
This clinical trial is one of many going on around the country on cancer in dogs, aimed not just at curing man's best friend, but at finding answers in medical science's war on human cancer. Humans and dogs have similarities in how both develop cancer. They also share other physical traits and the same living space.
Canine research isn't confined to cancer, with studies around the U.S. focusing on everything from spinal cord injuries to aging to whether having a pet dog makes us healthier. But unlocking the mysteries of cancer, from testing new drugs to trying to understand why benign lumps turn into malignant tumors, may pose the greatest potential benefits for man and man's best friend, experts say.
The American Kennel Club Canine Health Foundation has funded some 30 such trials in the past 15 years. Meanwhile, veterinarian researchers at 20 universities around the nation have formed the Comparative Oncology Trials Consortium to share information and cooperate in clinical trials on cancer in dogs, with the goal of better understanding and treating cancer in people.
"There are a handful of products that have been added to the market that were initially tested in pet dogs with cancer. There are many more in the pipeline," says Arlene Weintraub, author of the new book Heal, about comparative oncology between dogs and humans. "Over the last year or so there have been many developments in this area, in all sorts of cancer research."
For Valo's owner, it's about not only prolonging his life, but maybe playing a part in the greater battle against cancer.
"In a way, he is making his little mark on history," Rockwell says.
All 20 dogs enrolled in the cancer study are still alive, says Gerald Post, DVM, oncologist at The Veterinary Cancer Center in Norwalk, CT.
While it's too soon to say what role the clinical trial played in their survival, researchers are optimistic. The study is based on a vaccine developed at the Yale School of Medicine. First tested in mice, the vaccine's purpose is to encourage the animals to make disease-fighting antibodies to attack a tumor.
Post says the study is a new take on monoclonal antibody drugs that have been used in humans. In these drugs, the medication itself provides antibodies to fight tumors.
"Instead of making the antibodies externally, we have hopefully figured out a way to make the body make them itself," Post says.
If the study shows most dogs have developed the antibodies, researchers will do a second that looks at dosing and a third focusing on the long-term effects on tumors.
"We're really excited about it, because it could truly revolutionize how cancer is treated in dogs and people," Post says.
It's one of many projects that are part of the One Health Initiative, a global movement to look at all aspects of human, animal, and environmental health in a comprehensive manner. Canine research has allowed researchers to identify genes linked to different types of lymphoma in dogs that are also linked with lymphoma in humans. Researchers at Mississippi State University see promise in studying blood platelets in dogs with cancer to better understand how cancer spreads and how to stop it.
Dog research has already led to some drugs and therapies showing promise in human health. Weintraub cites Sutent, which is prescribed to battle advanced kidney and other cancers, as one such drug. Researchers have also begun human trials on PAC-1, which causes cancer cells to self-destruct, after successful results from canine studies. Some of this research is funded by the American Kennel Club Canine Health Foundation. Diane Brown, DVM, PhD, chief scientific officer for the foundation, is quick to differentiate this work from animal testing.
"Sometimes people think, 'Oh, this is about owners who are dropping their dogs off for research purposes,' and that's not the case at all. These are dogs that belong to people that continue to be cared for and live in their homes," Brown says.
"You'll have these veterinary specialists who are running trials that have access to all the latest tests and MRIs and equipment, so the dogs are still treated for their medical condition. They just happen to be having samples taken or having drug therapy that is still experimental."
Such treatments could cost pet owners thousands of dollars, she says, while these clinical trials are offered at reduced cost or sometimes for free.
And the potential benefits go far beyond cancer research.
Treating Spinal Injuries
At first glance, a dog's spine seems to have little in common with a human's.
But Jonathan Levine, DVM, says spinal injuries in dogs can be very similar. An associate professor at the Texas A&M College of Veterinary Medicine & Biomedical Sciences, Levine has been working for years on a treatment in dogs that could be used in humans.
He is compiling the results from a study of 90 injured dogs that received the treatment shortly after injury. It's designed to block enzymes released after an injury that can cause more permanent damage and stunt the healing process.
The hope is that, combined with surgery, rehabilitation, and other treatments, the drug will show enough promise to eventually be used in human trials.
"I think the reality is it's hard to find treatments for human spinal cord injuries. There are so many examples of failed trials and the hope for those of us working with dogs that are injured is we can speed discovery, that we can help the dogs, and we can help people. And we really believe in the potential of these dogs to do that," Levine says.
Do Dogs Make Us Healthier?
At the University of Arizona, scientists are looking to the bacteria in our guts to try to prove the adage that having a dog makes us healthier. Could the relationship between man and man's best friend be more than a social one?
"Dogs have evolved with humans over thousands of years, from the point in which we were trying to domesticate them," says research specialist Kimberly Kelly.
"We really wanted to see if there's something deeper that's going on and if that mechanism might actually be bacterial because of that evolution, the sort of 'old friends' idea," Kelly says.
Researchers paired shelter dogs with people who didn't own one and collected fecal, saliva, and skin samples from both. They wanted to see if the dog's presence changed the bacteria in the gut and eased digestion. They are also studying whether the bacteria dogs have could affect humans' allergies and their immune systems. Kelly expects to have preliminary results by early in 2016.
"Anecdotally, people would tell me their digestion was better. Who knows, that could be stress. The dog is bringing the stress down," Kelly says. They plan a larger study if results bear out.
It's already been a win for the dogs. Of the 16 in the study, study participants permanently adopted 14.
Sandie Kirchner and her husband hadn't had a dog in 20 years. But when the retired couple heard about the study, they volunteered.
Kirchner, of Tucson, AZ, doesn't know what biological effects came from having April, the 3-year-old Chihuahua mix, in the home. But their new best friend has made life better.
"I don't know if it actually changed the probiotics in my body -- probably it did. I know my husband's blood pressure dropped, so his cardiologist changed his medication," she says. "Having a dog in the house just makes us smile, so that makes us happier. I walk her a couple times a day, so I've met all kinds of new neighbors, so I guess that's improved my mental health."
SOURCES: Wtnh.com: "Breakthrough canine cancer vaccine clinical trial could benefit humans." News release, American Kennel Club Canine Health Foundation. One Health Initiative. Sciencedaily.com: "Researchers treat canine cancer, likely to advance human health." Vetmed.tamu.edu: "Research Offers Hope for Spinal Cord Injuries: How a Clinical Trial in Dogs May Help Human Patients." Bloomberg.com: "Can Dogs Help Cure (Human) Cancer?" Elvers, I. Genome Research, published online Sept. 16, 2015.Abcnews.com: "New Study to Investigate Whether Dog Saliva Can Help With Allergies."Sandie Kirchner, dog owner, Tucson, AZ. Marisa Rockwell, dog owner, Guilford, CT. Kimberly Kelly, researcher, University of Arizona. Diane Brown, DVM, chief science officer, American Kennel Club Canine Health Foundation. Arlene Weintraub, author, Heal, ECW Press, 2015. Gerald Post, DVM, The Veterinary Cancer Center.Jonathan Levine, DVM, the Department of Small Animal Clinical Sciences, Texas A&M College of Veterinary Medicine & Biomedical Science.