Teaching an old disease new tricks: In the hunt for cancer treatments, dogs are man's best friend yet again
The following story appeared in the May/June issue of The Post. Read the entire issue here.
At the UF College of Veterinary Medicine, researcher and UF Health Cancer Center member Rowan Milner, D.V.M., Ph.D., is immersed in two clinical trials that could ultimately improve the survival time for bone cancer and melanoma, a form of skin cancer. Milner is about halfway through a two-year study that uses a vaccine to induce an immune system response that slows the spread of osteosarcoma, a type of bone cancer.
For Milner, studying osteosarcoma is the natural extension of an earlier success. The ongoing study of 400 dogs with melanoma has already showed that a vaccine containing a particular antigen provoked the desired anti-cancer immune response that looks promising.
“You can stimulate the body to mount an immune response, and then see a significant response,” says Milner, the Hill’s associate professor of oncology and chair of the department of small animal clinical sciences.
Hundreds of pet owners with naturally occurring cancer have enrolled their dogs into Milner’s melanoma clinical trial, while others are participating in the early stages of the osteosarcoma trial. Because the immune responses and some cancers in dogs and humans are somewhat similar, what’s good for a cancer-stricken dog may also one day be good for its master.
“I get to do therapies in dogs that may result in me helping people’s pets. If we get the right answers, it could go into use in humans,” Milner says.
In the osteosarcoma trial, 20 dogs are receiving standard of care plus a vaccine containing an antigen similar to the one that has already created a positive immune response in dogs with melanoma. For comparison, 20 other dogs are receiving standard osteosarcoma treatment, allowing Milner to gauge the vaccine’s effectiveness.
Osteosarcoma is the most common malignant bone tumor, affecting 10,000 mostly large-breeds dogs a year in the United States. In humans, osteosarcoma usually affects children and young adults, attacking areas where the bone is growing quickly. Some 800 new cases are diagnosed in the United States each year. The five-year survival rate for humans can range from 60 percent to 80 percent for localized tumors, or less than 30 percent if it has already spread, according to the American Cancer Society. In the case of dogs, 80 percent to 90 percent will not survive past two years.
Milner says osteosarcoma is particularly challenging because it can regulate how the body tolerates cancer’s existence and might be switching off the body’s normal anti-cancer immune reaction. That’s why Milner and collaborators in the UF College of Medicine are also looking at another approach. They are developing a unique way to generate specialized cells that specifically target osteosarcoma. The technique, known as chimeric antigen receptor T-cell therapy, works this way: T-cells, a type of immune cell, are harvested from a patient and genetically modified to recognize a protein on targeted tumor cells. The engineered cells are then multiplied and returned to the patient’s bloodstream, where they go on to attack and kill cancerous cells.
The T-cell approach has the potential to significantly improve outcomes for osteosarcoma patients, something Milner says is urgently needed because survival outcomes for humans and dogs with osteosarcoma has not changed significantly in the last 20 to 30 years. Studying its effects in dogs is an important step toward being able to test it in humans during a clinical trial, according to Milner.
While the T-cell research is ongoing, Milner says he sees significant potential.
“We have just begun, but it’s possible that this kind of T-cell therapy could someday result in significant reductions in the cancer load in humans,” he says. — Doug Bennett