Canine cancer vaccine program shows early promise

It wasn't publicized, other than by word of mouth, and still the University of Wisconsin-Madison School of Veterinary Medicine was overwhelmed with requests. Since 1998, the school's oncology department has been producing an anti-cancer vaccine for dogs diagnosed with melanoma. Though it is still an experimental treatment, dog owners from all over the nation have wanted to participate in the study, on the remote chance that this would help their pet.

After promising results from work done in collaboration with cancer specialists from Arizona, California, and Michigan, the school has hired a full-time technician to produce the existing vaccine. The vaccine being used now has undergone a few modifications designed to increase its anti-cancer activity. "Not all dogs with melanoma respond to this treatment," cautions Ilene Kurzman, a researcher in the veterinary medical school's oncology section. "But those that do seem to do quite well."

She would like to continue working on the vaccine in the hope that this innovative anti-cancer strategy will translate into similar novel treatments in people with cancer.

Melanoma, the equivalent of one form of skin cancer in humans, is very aggressive in dogs. It usually manifests itself in or around the mouth or toes. Despite conventional treatment, 75 percent of dogs with oral melanoma will die within one year.

But about 40 percent of dogs with a melanoma tumor present responded to a vaccine created from actual melanoma tumor cells. In about 12.5 percent of the treated dogs, the tumor completely disappeared. While the current results are promising, funding limitations reduce the program's ability to take the next step in improving the vaccine and increasing the percentage of animals that respond, Kurzman says.

According to Kurzman, the vaccine is created from dog melanoma cells that are grown in the laboratory. The cells are treated so they can no longer divide and cause a tumor. DNA is then inserted into these cells, which directs the cells to secrete an immune stimulant. This combination of cells and immune stimulant, when administered as an injection into the patient's skin, has been shown to stimulate the immune system to specifically fight against the melanoma cells.

Dogs that first had surgery for their melanoma and then received vaccine lived cancer-free for approximately twice as long as dogs in previous studies that did not receive the vaccine. Further work is needed to improve the vaccine so that a higher percentage of dogs with melanoma will respond. "It's the closest thing to a miracle I've ever seen," says Maggie Hoefling, of Largo, Florida. Following vaccine therapy, her husband Gus's 14-year-old beagle, Mack, not only lived an additional two years, but thrived. And that's after their local veterinarian gave Mack only four months to live when he was first diagnosed with melanoma. Mack has since died, but he died of congestive heart failure, not cancer, and had gained two more years of quality life.

Source : University of Wisconsin-Madison