Giving cats, bears a fighting chance

January 31, 2001|By Katherine Spitz | Katherine Spitz,KNIGHT RIDDER NEWSPAPERS

CLEVELAND - Dr. Chris Bonar worries about his massive patients. Although they can tear him to bits with swoops of a giant paw, they can easily be felled by a foe of their own: cancer.

Gaia, Cleveland Metroparks Zoo's lone female tiger, is at extreme risk of breast cancer - she is 10 times more likely to get the disease than her human counterparts. And the zoo's nine bears are at high risk of contracting pancreatic or bile duct cancer, which are particularly aggressive in animals as well as humans.

Bonar, associate veterinarian at the zoo, wants to detect his patients' cancers earlier, when the hopes for treatment are better. But while early detection helps humans, tigers can't do a monthly breast exam, and a bear can't complain to his doctor that he feels sick.

So, in a scientific twist from the usual animal-research-helps-humans scenario, Bonar is borrowing from advances in human medicine in an attempt to help his four-legged patients.

The research, involving the science of tumor growth, is the first of its kind in the country using zoo animals. Eventually, Bonar hopes he and other zoo veterinarians can treat cancers in the big cats and bears extremely early, and so increase their survival rates.

This is especially important because the exotic animals are endangered. For instance, there are more Siberian tigers in zoo conservation programs - about 600 in all - than there are in the wild, said Cleveland zoo spokeswoman Esther Newman.

So when cancer strikes a zoo tiger, it's a tremendous loss.

"Virtually every female tiger that I've autopsied in the last 20 years has had breast cancer," said Cleveland zoo veterinarian Dr. Albert Lewandowski.

A Harvard University honors graduate, Bonar works in a windowless office a little larger than a closet. Although known as a brilliant researcher by his peers, his manner is as unassuming as his work station.

"For me, that's one of the exciting things," he said. "OK, what can I take from the cutting-edge aspect of medicine and apply it to animals? That's what really turns me on."

The 34-year-old Pittsburgh native always knew he wanted to treat animals. While at Harvard, he grew interested in what is known as angiogenesis (blood vessel growth), a field of scientific study developed by researchers at that university in the 1970s.

Angiogenesis has as its premise that since adults only grow blood vessels for wound repair and reproduction, when growth factors are detected in blood, it signals the presence of disease.

Researchers in the field come from different medical specialties, such as ophthalmology, surgery and dermatology. They have isolated 20 such factors that can be detected in human blood when cancer and other diseases are present, often in their early stages, said Dr. William Li, chief of the Angiogenesis Foundation, a Cambridge, Mass., organization devoted to research and public education.

Several years ago, Bonar decided he wanted to see whether animals have the same growth factors when they develop tumors. He quickly got support for his research from foundation colleagues.

"They love the opportunity to be involved with tigers and lions," he said, noting that physicians like a change of pace.

When Bonar joined the foundation board as the only veterinarian, he did so with the stipulation that his physician colleagues would support animal research, said Li, an internist who also is a clinical instructor at Harvard Medical School."[Bonar] made the case that in the quest to develop human medicines, thousands of animals have given their lives as a necessary part of research," Li said. "And yet many drugs fail the human test stage, then they are discarded and animals never get to benefit from them."

Bonar's research involves collecting blood samples from tigers and bears from the Cleveland zoo and zoos and parks across the country, including those in Detroit, Columbus, St. Louis and Florida.

The samples, which include blood from healthy animals, are being sent to a pharmacological researcher at the National Cancer Institute in Bethesda, Md. The researcher is analyzing the samples to look for two growth factors, bFGF and VEGF, found in blood when tumors are present.

The research is in its early stages, but so far, Bonar said, the studies show that growth factors in animal blood signal the same problems as they do in humans. Now, he wants to do the studies on a larger scale.

Unlike many types of research, these studies don't distress the zoo animals, Bonar said. Blood samples are routinely taken during the zoo animals' yearly physicals, when they are about to be released from quarantine or when they are shipped to another facility. And unlike humans, the animals are asleep during the procedure.

Although the Cleveland-based study aims to help animals, both Bonar and Li believe the research also will eventually benefit humans.

"In any case, when you can demonstrate that something's effective with an animal, whether it's a laboratory animal or a zoological specimen, you support the use of these diagnostic treatments in humans as well," said Bonar, who also is doing research that could help treat common cancer in domestic cats.

The next step in the research will be to treat the animals with anti-angiogenic therapy, designed to starve a tumor by cutting off its blood supply. Special drugs - 53 in all - are now being tested in clinical drug trials both nationally and internationally, Li said.

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