Your dog's intestinal microbiota could predict cancer progression

When we talk about cancer in dogs, we touch on one of the deepest fears of those who share their lives with an animal. The figures describe a difficult reality: in the United States, around 6 million dogs are diagnosed with cancer every year. Today, tumors remain the leading cause of death in the canine population.

Behind every statistic, there are families, emotional bonds, broken routines and the question on everyone's mind: how much time do we have left together?

Yet scientific research continues to make progress. And it's doing so by taking a path that, just a few years ago, would have seemed almost secondary: that of the intestinal microbiota, the set of bacteria and micro-organisms that live in the gut and have a profound influence on the immune system. A new study published in the scientific journal Veterinary Oncology suggests that the very balance of these intestinal microbes could help predict dogs' response to cancer immunotherapy.

A discovery that opens up very concrete prospects and, if confirmed, could change the way veterinarians and families make therapeutic decisions.

Intestinal microbiota and immunotherapy: what researchers have discovered

Human medicine has long observed that certain gut microbiota profiles are associated with better outcomes in cancer patients treated with immunotherapy. Some bacteria seem to favor the immune system's response, while others seem, on the contrary, to hinder it. This raises the inevitable question: could the same mechanism be applied to dogs?

To find out, a team of researchers followed 51 cancer-stricken dogs included in a clinical trial conducted at the Bridge Animal Referral Center in the USA. The animals received an experimental immunotherapeutic vaccine that had already shown promising results in previous studies.

The vaccine acts by inhibiting two proteins involved in tumor growth, EGFR and HER2, which are often over-expressed in certain forms of cancer. The aim is to stimulate the immune system to recognize and fight tumor cells more effectively, slowing disease progression and improving quality of life.

But the immune system doesn't work in a vacuum. It's immersed at the heart of a complex ecosystem, an "invisible city" populated by bacteria, fungi and other micro-organisms in constant dialogue with our natural defences.

By analyzing rectal swabs taken from the dogs prior to treatment, then comparing this data with their subsequent survival, the researchers identified eleven types of bacteria associated with the outcome of therapy. Four of these were linked to longer survival after immunotherapy, while seven were associated with shorter life expectancy. This result was independent of breed and type of cancer diagnosed.

This means that the gut microbiota could influence the immune response even in the case of cancers that do not directly affect the gut, such as osteosarcoma (bone cancer) or hemangiosarcoma, which affects blood vessels.

A new perspective on cancer prognosis in dogs

This study is a first step, and does not yet go into detail on the biological mechanisms that explain this correlation. However, one fact remains certain: the intestine appears to play an active role in modulating the immune response against the tumor.

According to Natalia Shulzhenko, a researcher specializing in host-microbiota interactions at Oregon State University, a simple swab can be used to analyze the immune response to a tumor.According to Natalia Shulzhenko, a researcher specializing in host-microbiota interactions at Oregon State University, a simple microbiota test could, in future, help predict a dog's response to cancer treatment. Veterinarians would then be able to make more accurate prognoses, and owners could make more informed choices about the course of care.

The implications go beyond simple prediction. If certain bacteria enhance the efficacy of immunotherapy, it's entirely possible to imagine targeted interventions on the microbiota, at the level of the animal's immune system. We're still in the early stages of this process, and we're still working on the best way to optimize the intestinal environment before or during treatment.

We're still in the early stages of this research, and veterinary immunotherapy remains a rapidly evolving field. Nevertheless, the idea that the intestinal ecosystem can help determine the prognosis of cancer in dogs opens up a perspective that combines science and hope. Attention then shifts to an often invisible but absolutely central aspect: the body's internal balance.

Taking care of our pets' intestinal health could, in future, become an integral part of oncology strategies.

Source: Veterinary Oncology