When her black Lab, Emmy, started limping in 2008, Kathi Streeter suspected the normal aches and pains of aging. Then came the devastating diagnosis: osteosarcoma, a deadly bone tumor. Osteosarcoma affects humans, too—mostly children, whose long-term survival rate, if the cancer spreads, is under 40 percent. Though Emmy died in May at the ripe old age of 13, she gained nearly three years of healthy living, and one day her treatment may help those kids.
[Learn more about how dogs help mankind in Mysteries of Science: Amazing Animals.]
In her quest to save Emmy, Streeter learned about a study underway at Colorado State University's Animal Cancer Center in Fort Collins, about 100 miles from her home in Franktown, Colo. It was testing a gene therapy that could be injected straight into osteosarcoma tumors. The gene delivers a molecule designed to induce the cancer cells to self-destruct. Veterinarians there wanted to see how well dogs reacted to the treatment, as part of an effort to determine whether it might also be investigated for use in children.
Streeter is a cancer survivor herself—in 2004, she underwent a double mastectomy and chemotherapy to treat breast cancer—and didn't hesitate to sign Emmy up. After the injection, CSU vets gave Emmy the standard treatment, too: amputation of her leg plus six rounds of chemo. They're now evaluating how the injection affected the tumor. Although the results of this trial have not yet been published, previous trials suggest that the therapy may enhance the immune system's ability to combat the tumor.
CSU is one of 20 participants in the Comparative Oncology Trials Consortium (COTC), a growing program started in 2003 and managed by the National Cancer Institute to study cancer in dogs and to recruit them for clinical trials of new treatments. The goal is more effective, more personalized treatments for man as well as his best friend. "Several tumor types in dogs mimic human cancers in their biologic behavior and genetic signature," says Susan Lana, associate professor of clinical oncology at CSU. "Dogs can help us try to answer questions like, 'Why does this cancer spread?' and 'Are there genetic pathways we can explore for treatment?' "
Dogs are ideal models, Lana says, because they're genetically similar to humans and share the same environment. They develop cancer naturally, unlike mice and rats, which must be engineered to have the disease. And dogs are big enough to undergo MRIs as well as blood tests and biopsies, so scientists can better observe changes in the cancer over time. Thanks to advances in genomics and gene sequencing, researchers have established which canine cancers are most similar to their human counterparts. Besides osteosarcoma, they include prostate and breast cancer, melanoma, soft tissue sarcoma, and non-Hodgkin's lymphoma.
Vaccine success. Comparative oncology has already produced some success stories. In 2010, the U.S. Department of Agriculture approved Oncept, a therapeutic vaccine for dogs with melanoma. Therapeutic vaccines are designed to mobilize the immune system to make antibodies against cancer cells, which ideally then destroy the cells and keep the cancer from coming back, and they've long been the holy grail of cancer drug development. But many of the vaccines tested have proved disappointing. If Oncept is any indication, dogs might hold the key to fine-tuning cancer vaccines. Some dogs in the Oncept trials lived more than a year after their diagnosis—far outpacing the typical lifespan of one to five months with conventional therapies.
The data from the dog trials were impressive enough to prompt the Food and Drug Administration to green-light a small human trial of a similar drug. Jedd Wolchok, a physician at Memorial Sloan-Kettering Cancer Center in New York and the drug's codeveloper, is hoping a pharmaceutical company will fund the large clinical trials that would be needed to get the human version of the vaccine approved. "These trials can take over five years and they're exorbitantly expensive, but the risk could lead to a long-term payoff," he says.