ted States that he realized there were strong connections between cancers in people and domestic animals.
One such connection surfaced in the 1990s with the gene p53. The subject of thousands of research papers in that period, p53 is a gene encoding a protein that was found mutated in half of all human tumors. Given that, like humans, cats, dogs and horses also develop cancer, Chen wondered: Would mutant p53 be present in their tumors as well? A review of the sparse veterinary literature revealed the answer — yes — and Chen’s fascination with the molecular similarities between animal and human cancers was born.
— Xinbin Chen, researcher
Studying cancer in domestic animals makes good scientific sense, Chen says. Pets live in the same environment as people do, often sharing the air, water, food and sleep patterns of their owners. Like humans, these animals develop tumors that arise spontaneously, grow fairly slowly and are associated with old age. And dogs, cats and horses are more closely related genetically to humans than are the laboratory mice typically used in research.
“It’s puzzling,” the bespectacled Chen says with a chuckle. “Cancer in mice has been cured many times. But often the drugs that work in mice don’t work in humans. We need some new animal models.”
That’s the idea behind comparative oncology, which UC Davis researchers began exploring many years ago. In the 1960s, for instance, scientists studied dogs in order to develop tumor radiation protocols for human patients. More recently, the UC Davis Cancer Biology in Animals program tested a range of new anti-cancer drugs in cats and dogs. Chen is now broadening the program to include horses and aims to focus studies on three kinds of cancer common in companion animals: melanoma, osteosarcoma and lymphoma.
To get the new program and laboratory up and running, Chen has been busy assembling and training a team of veterinarians to study and treat cancer in domestic animals. He also has hired a drug trial coordinator — the first ever for the veterinary school — to track data on how animal patients respond to experimental therapies. Ultimately, he hopes to learn more about the role of p53 and other genes in tumor growth and use that knowledge to develop more effective cancer treatments for people and their pets.
Already his team is testing a drug that might one day be deployed against non-Hodgkin’s lymphoma, a cancer of the immune system that each year strikes about 60,000 Americans and kills 18,000. The compound is a small peptide that appears to inhibit the progression of the disease. Kit Lam, chief of the Division of Hematology and Oncology at the UC Davis Cancer Center, is now giving the promising drug to cats and dogs with lymphoma and collecting data on the results.
“When we use cats and dogs to test drugs — instead of lab mice — it’s much more likely that they will work in humans,” Chen says.
This advantage is not lost on drug companies, notes Chand Khanna, director of the comparative oncology program at the National Cancer Institute’s Center for Cancer Research in Bethesda, Md. “New tools for studying cancer in companion animals are now helping us to find out why cancer goes away with some therapies and doesn’t go away with others,” he says. “That information is very valuable to the pharmaceutical industry.”
The UC Davis program, he adds, will contribute research data to a national Comparative Oncology Trials Consortium made up of 14 university re-search centers. The consortium collaborates with the U.S. Food and Drug Administration and with pharmaceutical companies.
“The goal,” Khanna explains, “is to learn more about new therapies and to use that information to develop the best human clinical trials possible.”
Chen’s particular interest is to find new drugs that can be used in combination with radiation therapy to prevent metastasis — the spread of cancer throughout the body. That’s what kills patients with osteosarcoma, a bone cancer that is the second major cancer in children, and also is common in dogs. Chen is testing compounds that bind to mutant p53