Good dog

You share more things in common with your dog than you think, and these similarities are the focus of research at the University of Saskatchewan (USask) that’s aimed at investigating osteosarcoma, a type of bone cancer found in dogs and humans.

A research team led by Dr. Behzad Toosi of the Western College of Veterinary Medicine (WCVM) is studying the characteristics of osteosarcoma that are common to both species. This relatively new approach to studying cancer is known as comparative oncology, and it promises to speed up the development of new treatments for dogs and people.

Comparative oncology seeks to bridge the gaps between laboratory research and human clinical trials by combining research from other fields such as veterinary medicine.

“[Dogs] share a household with you and they develop the same kinds of cancers as you, and those cancers are very, very similar genetically or molecularly,” explains Evelyn Harris, a graduate student and member of Toosi’s research team.

“It’s interesting to study comparative oncology because it is a stepping-stone between the mouse model and the human model.”

The researchers’ recent focus has been on receptors, small proteins found on the cells’ surface. Although these receptors provide many essential functions to cells in the body, they’re also known to be easily “hijacked” by cancer cells and used for their benefit. But if researchers could use these receptors to specifically target cancer cells and deliver treatments, they could ultimately reduce the side effects of chemotherapy drugs.

In osteosarcoma the small molecules of interest are erythropoietin-producing hepatocellular (Eph) receptors. Although they’re found on most cells, previous research indicates that some subtypes of these receptors are overabundant in many human cancers.

“These [receptors] are emerging as some molecules that are very important in regulation of invasiveness of different cancers in humans, but they haven’t been studied in dogs,” says Toosi, an assistant professor at the WCVM. He also holds the college’s Allard Research Chair in Oncology.

After exploring these receptors to determine their role in the progression of dog cancers, the WCVM team has successfully demonstrated the overabundance of some receptor subtypes in osteosarcoma cancer cells from dogs.

Further investigations of some Eph receptor subtypes revealed that they play an essential role in osteosarcoma by enabling cancer cells to grow and move faster — contributing to the cancer’s aggressiveness.

Since there have already been some attempts to target these receptors in human cancers, Toosi thinks it’s possible to target and interfere with these receptors as a means of more effectively treating osteosarcoma in dogs.

“These receptors are very promising for dog malignancies,” says Toosi. “They could lead to new clinical interventions for treatment of dog osteosarcoma.”

Traditionally, cancer therapy for dogs with osteosarcoma involves more invasive treatments such as radiation and chemotherapy — treatments with side effects that often trump those caused by the cancer.

“A lot of people will amputate the limb to get rid of the primary bone tumour and then only get a few more months with the pet,” says WCVM graduate student Dr. Jessica Sharpe, another member of Toosi’s research team.

Comparative oncology may be key to developing new treatments more quickly — and that’s promising for humans and their furry friends. Dogs have a much shorter lifespan than people, and they develop osteosarcoma naturally and at a higher rate than humans. As a result, new treatments can be taken to canine clinical trials more quickly than in their human counterparts.

“Since the biology of cancer is similar between dogs and humans, these investigations in dog clinical trials can inform further research or clinical trials conducted in humans,” says Toosi.

Maya Kliewer of Saskatoon, Sask., is a WCVM veterinary student who worked as a summer research student in 2021.