Pets: How research into dog, cat cancers is helping develop treatments for humans

We pamper them. We feed them, sometimes from the table. They sit on our laps and often sleep in our beds. They give us unconditional love. So, it’s not too surprising that we sometimes spend enormous sums of money to take care of pets when they get sick. What is surprising is that their biological similarities to us provide researchers with the tools to help us when we get sick. Colorado State University’s Nicole Ehrhart, director of the Laboratory of Comparative Musculoskeletal Oncology and Traumatology (among many other titles), is helping to lead the way in showing how our best four-legged and furry friends can help treat cancers and other ailments that plague humans.

In 1991-95, when Ehrhart was still a surgery resident, she visited a bone cancer camp for kids 40 miles west of Denver called High Hope Camp. (skyhighhope.org) While there she met a young lady who had just undergone an amputation to control a bone cancer or sarcoma.

“I became inspired,” Ehrhart said, “ to understand more about how helping dogs with cancer had an enormous potential to help people and vice versa.” She became so inspired, in fact, that she decided to devote her career to this field.

Although fido might seem like a very distant cousin at best, we share 80 percent of a dog’s genes, as revealed when the complete dog genome was decoded in 2003. Compare this to the 67 percent of genes we share with rats, the typical test subject used for much laboratory work. Moreover, dogs live with us and grow old with us, providing the opportunity to acquire cancers and other diseases associated with increasing age. Ehrhart mentioned in a recent article on the subject that, “lymphoma and bladder cancers that spontaneously arise in pet dogs are microscopically and molecularly identical to cancers in people. Many of the genetic mutations that drive cells to become cancerous in people are the same mutations that cause cancer in dogs.”

Cats also make good health partners. A 2007 paper in the Cold Spring Harbor Laboratory Press noted that cats have 250 naturally occurring hereditary disorders, many of which they share with us, including a kind of degenerative eye disease called retinitis pigmentosa. Cats also serve as good models for HIV/AIDS. Ehrhart noted that “Chronic kidney disease is common in aged pet cats and studies aimed at eliminating this disease, also seen in elderly people, are underway at CSU.”

Cancer diagnoses are on the rise in both dogs and people. Partly, this may be because both dogs and people are living to an older age, but our pets also may suffer from poor diet, lack of exercise, and pollutants indoors and out. Ehrhart said that there is some evidence, for example, that “oral tumors in cats are more common in households where there is secondhand smoke exposure, presumably because they groom their fur and are exposed that way.” She goes on to say that the cat’s oral tumors resemble those in human smokers.

Our similarities with our mammalian “friendamals” also include parallel responses to treatments for cancers. For example, research on osteosarcomas, or bone cancers, in dogs led to several breakthroughs in treating osteosarcoma in children, like the one that afflicted the child Ehrhart met at High Hope Camp. Recently, a form of immunotherapy used on dogs prevented the spread of bone cancer to the lungs, improving their survival prospects. This work, in turn, led to the FDA giving fast-track status for trying the same therapy in humans.

This field of comparative oncology brings together basic scientists, cancer specialists, veterinarians and physicians in a way that may create new synergies between researchers and lead to better treatment for human beings. So, some of the bills we incur to keep our pets healthy may eventually help us as well—unless are pets of choice are lizards or spiders. The biological gaps between these latter creatures and us may be a little too broad to leap; at least as far as health care is concerned.

Ehrhart still volunteers as a camp counselor at High Hope Camp. It keeps her focused and inspired. But now, she says, “I also bring my graduate students to camp so they can understand how urgent the need is to continue research to benefit both humans and pets with cancer.”

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