ool — 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 and can restore its normal function as a tumor suppressor.
“If this works well in dogs, then maybe we’ll have better justification to try it in kids,” he says.
In the longer term, the UC Davis program on compar-ative oncology could yield entirely new approaches for treating these three cancers, as clues reveal discoveries about other key genes besides p53. Chen already sees a golden opportunity to learn more about melanoma — the most lethal form of skin cancer — by studying the genetics of the disease in horses.
“Why are certain breeds of horses more susceptible to melanoma?” Chen asks. “This is veterinary medicine, but it may in the future apply to human melanoma.”
Because horses tend to be inbred, their pool of genes shows limited variety.
Information about their breeding is also readily available. By examining DNA from horses with and without melanoma, Chen hopes to find new genes associated with the disease. Then, he’ll search the human genome for comparable genes and investigate whether these might be good targets for new kinds of melanoma treatments.
In the meantime, animal patients should benefit from the research, as Chen’s team tries some of the latest therapies for humans on ailing pets. Animals with melanoma and osteosarcoma, for example, will be given an antibody-based treatment to see if the drug helps prevent metastasis, as it does in cases of human breast cancer.
“We may not be able to cure someone’s pet now, but in the future someone else’s pets will get better care,” says Chen. And there’s an indirect benefit, too. “When a pet lives longer, it increases the owner’s lifespan,” he notes. “Animal health is part of human health.”