Dogs Help in Hunt for New Cancer Drugs
MONDAY, March 23 -- Joe Bauer got the call on a Friday afternoon.
A 10-year-old bichon frise named Oscar had developed anal sac adenocarcinoma, a particularly virulent cancer in dogs, and had been given only three months, at best, to live. The dog's owners, from Milford, Mass., were heartbroken and planned to have Oscar put down the next day.
Instead, Bauer, who at the time was a staff scientist at the Cleveland Clinic's Center for Hematology & Oncology Molecular Therapeutics, shipped an experimental cancer drug free-of-charge to Oscar's veterinarian -- essentially enrolling Oscar in a clinical trial that could end up benefitting not only suffering dogs but humans as well.
Treating dogs as a prelude to finding new cancer drugs for humans is an idea that's catching on.
"Dogs are benefiting more and more as [people] recognize the value of studying new cancer therapies -- not just drugs -- in dogs," said Dr. Ann E. Hohenhaus, a staff veterinarian and board-certified dog/cat oncologist at the Animal Medical Center in New York City. "There are a couple of reasons why the dog is so good."
For one thing, the mice usually studied in cancer research are genetically bred to develop tumors. Dogs, like humans, spontaneously develop tumors.
"The tumors we ultimately want to treat in people spontaneously happen because people have darn bad luck," Hohenhaus said. "The same thing is true for dogs. That aspect of tumors in dogs is fabulous in terms of mimicking what happens in humans."
Also, not only are dogs similar to humans in their genetic makeup (certainly more similar than mice), they are also exposed to the same environmental factors that humans are.
Experimental chemotherapy drugs might garner response rates of 80 percent or higher in mice, but that figure often plunges to 10 or 15 percent when applied to humans, added Bauer, who said he now directs scientific research at the Bauer Research Foundation in Port St. Lucie, Fla.
It's been five years since Oscar's death-sentence reprieve with the new drug, and he's still going strong.
Since then, three other dogs have been treated and have responded to the drug, called nitrosylcobalamin (NO-Cbl), without any negative reactions, Bauer said. He was to present the findings Monday at the national meeting of the American Chemical Society in Salt Lake City.
The research field appears so promising that the U.S. National Cancer Institute has established the Comparative Oncology Program to evaluate chemotherapy drugs in dogs.
And the first U.S. canine tumor tissue bank started accepting tissue and blood samples from dogs with cancer in 2007. The new "biospecimen repository" facility lies adjacent to the National Cancer Institute's own library of human cancer samples.
NO-Cbl works like a "Trojan horse," binding to vitamin B12 receptors on cell surfaces. This blocks the action of B12, which aids and abets the potentially deadly divide-and-multiply process of cancer cells.
Since Oscar, Bauer has treated a 13-year-old giant schnauzer named Haley with thyroid cancer and a 6-year-old Golden Retriever named Buddy with malignant peripheral nerve sheath tumor.
Buddy's tumor shrank 40 percent after 10 months of daily treatment, he said. Haley's shrank by 77 percent.
Bauer's group is now doing research with 10 dogs. They will be tracked for a year with the help of their own veterinarians. Based on the results of that research, Bauer said, he hopes to file for an investigational new drug application for NO-Cbl from the U.S. Food and Drug Administration for a phase I clinical trial on humans.
"There's a great inequity for drugs available for veterinary use and those available for human use," Bauer said. "Most of those used to treat dogs and other pets were developed in the 1950s."
Hohenhaus added: "This helps my animal patients have access to treatments they wouldn't have access to otherwise. We look at this as a benefit to both species."
Learn more about this aspect of research and treatment at the National Cancer Institute's Comparative Oncology Program.
Posted: March 2009
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