Vets learn about human breast cancer by treating tumors in shelter dogs
In an innovative program at the University of Pennsylvania, veterinary oncologists are learning about the progression of human breast cancer by treating mammary tumors in shelter dogs.
The New York Times
By the time the elderly woman surrendered the 10 dogs living in her mobile home in rural Maryland, the shih tzus were unkempt and full of fleas and had gone years without their shots. A cream- and mushroom-colored female named Akyra, with a sweet disposition and a comical underbite, was in such bad shape that volunteer rescue groups declined to take her in.
Akyra’s mammary glands were riddled with tumors, including one the size of a golf ball. She would be hard to place in a home, and the medical care she needed would be expensive. The tumors could be cancerous.
“When my husband called and said they were going to leave one of the dogs behind because she had mammary tumors, I said, ‘No, you’re not!’ ” said Bekye Eckert, 49, a dog lover who lives outside Baltimore and has cared for several animals with mammary cancer.
Eckert arranged for Akyra to be enrolled in an innovative program at the University of Pennsylvania, where veterinary oncologists are learning about the progression of human breast cancer by treating mammary tumors in shelter dogs.
Like breast cancer in humans, tumors of the mammary glands are among the most common cancers in female dogs. Most pet owners never see this type of cancer because it is rare in animals that are spayed at a young age. Mammary cancer in dogs is fueled by estrogen, as it is in humans, so removing a dog’s ovaries greatly reduces the risk.
But among strays, females used as breeders in puppy mills and other unspayed female dogs, one in four has tumors.
Mammary cancers in dogs respond to many of the chemotherapy drugs that are used in people, and feature some of the same molecular abnormalities. As in humans, the risk of tumors increases with age, though some breeds, especially smaller dogs, develop the cancer at higher rates than others.
Because dogs typically have 10 mammary glands and often develop tumors in several glands at the same time, they present a unique research opportunity, enabling scientists to study lesions that are at different stages of development — from benign to cancerous, and at transitional stages — all in the same animal.
“The dog gives us the potential to answer the question: When did something go wrong at the molecular level?” said Dr. Karin Sorenmo, chief of medical oncology at Penn Vet’s Ryan Hospital, who founded the Penn Vet canine mammary-tumor program in 2009. “We can also study the benign tumors and ask: What’s different in that one tumor that doesn’t change and become malignant versus another one that does change?”
This field of research, called comparative oncology, is used to improve the understanding of the biology of cancer and to fine-tune treatment for humans. In the process, shelter dogs get access to treatment.
“Every cancer that develops in a dog develops in a human, and for the most part, the reverse is true as well,” said Dr. Chand Khanna, who developed the comparative oncology program at the National Cancer Institute’s Center for Cancer Research.
Each year about 6 million dogs and a similar number of cats develop cancers, including non-Hodgkin’s lymphoma, lung cancer, prostate cancer, head and neck cancer, melanoma, soft-tissue sarcoma and osteosarcoma, as well as mammary carcinoma.
These spontaneously occurring cancers have a diversity of cells that more closely approximates the disease in humans than, for example, a cancer cultivated from a single cell in a mouse, Khanna said.
By the time Eckert brought Akyra to Penn Vet’s Ryan Hospital in mid-August, the dog no longer had fleas. She had been bathed, vaccinated, spayed, dewormed and groomed. Her hair was pulled up in two little pigtails atop her head.
Akyra wasn’t the only mammary-tumor patient that day. Puddles, a fluffy 5-year-old Maltese with a large tumor, was scheduled for surgery. Like other dogs that are part of the program, she wore an “I am a survivor” tag with a pink-ribbon logo permanently affixed to her collar so that anyone who adopts her will know that she is part of a clinical trial and must return to Penn Vet for follow-up care.
Astrid, a Maltese mix with 10 mammary tumors, was also being readied for surgery, and Amy, a rail-thin Rottweiler with a history of mammary cancer, was brought in to see if she qualified for the program.
A stroke of luck led Sorenmo to her chief collaborator, Olga Troyanskaya, a Princeton University bioinformatics professor who uses computer algorithms to study gene function and regulation. She happened to bring her 13-year-old German shepherd, Jessie, to Sorenmo for treatment in 2006.
“I heard she was the best cancer vet in the area, and I bullied my way in to seeing her on short notice,” Troyanskaya said. “I don’t think we ever figured out what Jessie’s primary cancer was, but we connected specifically about research, and that’s how this all started.”
Generally, two sets of tumor samples are taken from each dog, one for the pathology lab and one for Troyanskaya to use for molecular analysis. Astrid, for example, had tumors in seven mammary glands that were mostly benign. The largest proved to be malignant.
Such a large set of samples is a gold mine for Troyanskaya, who is looking for changes in the expression of a specific gene or group of genes, or pathways linking groups of genes as the tumor becomes malignant.
“If we find a handful of changes in gene or pathway behaviors that we are reasonably confident are involved in cancer progression, then we can go to human cancers and see what they’re doing there,” she said.
Troyanskaya’s great hope is to identify changes in gene expression that explain the progression from premalignancy to malignancy, and use the new understanding to improve diagnosis and treatment, perhaps even finding drugs that can thwart the process.
In the meantime, stray dogs are getting free cancer treatment that makes it easier to find them permanent homes, and they are promised care for any recurrence. More than 100 dogs have been through the program; several have been adopted by women who also survived breast cancer.
For Akyra, there was good news. She had surgery in August, and veterinarians removed the large tumor and three smaller lesions. The pathology report gave her a clean bill of health: None were cancerous.
She was adopted by Beth Gardner, a relocation consultant in Devon, Pa.
“She’s just a lovebug,” Gardner said. Akyra and an older male shih tzu, Peyton, are spending their days roaming several acres of property.
“How fantastic is this?” Eckert said. “If not for this program, this dog would probably have been put down.”