Canine cancer patients receiving a new form of immunotherapy lived longer or shorter depending on the composition of their microbiome, the community of organisms living in their gut.
Results of the clinical trial led by Oregon State University scientists were published in Veterinary Oncology.
The findings signal new hope for the nearly half of U.S. households with at least one dog, suggesting that personalized medicine and better outcomes may one day be realities for the roughly 6 million dogs diagnosed with cancer each year, OSU's Natalia Shulzhenko said.
There are more than 87 million domesticated dogs in the U.S. alone, and approximately one in four will develop cancer at some point in its life. More than 4 million dogs die of cancer annually; about half of all dogs that reach age 10 will succumb to cancer, the leading cause of canine death.
"Our study is a first step toward using the gut microbiome as a tool to develop prognoses and to manipulate cancer, not just in dogs, but potentially as a model for human treatments as well," said Shulzhenko, who studies host-microbiota interactions at OSU's Carlson College of Veterinary Medicine.
Co-led by Andrey Morgun of the OSU College of Pharmacy, the research involved 51 dogs of various ages and breeds that had been diagnosed with a range of malignancies, including cancer of the bones and blood vessels. Each dog was treated with a new type of cancer vaccine designed to trigger its immune system to block two cancer cell proteins that tell the cells to grow and divide.
Prior to treatment, the scientists collected rectal swab samples from the dogs for microbiome analysis. Trillions of organisms make up the canine microbiome, with 240 species accounting for more than 80% of the microbial community.
Amid all of those organisms, some connections were clear, Shulzhenko said. Scientists found 11 specific types of bacteria that were linked to how long the dogs lived - some were positive indicators, associated with longer survival, while others were associated with shorter survival.
"In the future, an analysis of a microbiome swab could help predict how well a dog might respond to a cancer treatment," she said. "This allows pet owners and vets to make more informed decisions about care. And now that we know certain bacteria are linked to survival, we can explore ways to 'fix' a dog's gut microbiome to help the vaccine work better and help the dog live longer."
The National Cancer Institute of the National Institutes of Health provided funding for the study, as did the Canine Cancer Alliance and the Biomedical Sciences Department of the Carlson College of Veterinary Medicine.
The collaboration included scientists from the National Cancer Institute, Yale University and the Bridge Animal Referral Center, as well as OSU's Vini Karumuru, Stephanie Nuss, Marina Elliott, Isaiah Shriver, Chih-Min Chao and Ryan Berriatua.
