The Norwegian University of Life Sciences conducted research on immune cells called M2 Macrophages in visceral and non-visceral Hemangiosarcoma tissue sampled from untreated dogs.
Macrophages are a type of white blood cell that surrounds and kills microorganisms, removes dead cells, and stimulates the action of other immune system cells. They can either help the body fight diseases or switch their function and help the disease grow. When they help cancer spread, they're known as tumor-associated macrophages (TAMs).
The study exhibited that TAMs are crucial components of the tumor microenvironment and the metastatic niche - critical for tumor development and spread. They promote tumor invasion and tumorous cell survival in circulation while inhibiting the adaptive immune response, among other processes. It also stated that the behavior of these macrophages in healthy tissue compared to tumor tissue might shift due to the influence of cancer.
Fewer investigations have focused on TAMs in dogs. However, studies on humans and rodents suggest a similar trend where a higher number of TAMs is associated with worse outcomes in canine cancers, such as mammary tumors and Hemangiosarcoma.
In the past decade, there has been significant interest in targeting TAMs as a strategy for cancer therapy. Three techniques were explored: depletion of TAMs to reduce their number within the tumor, inhibition of TAM recruitment to the tumor site from the bloodstream, and reprogramming of TAMs to change their behavior to make them attack the tumors rather than support them. Trials focusing on depletion and inhibition have not been successful, so research is increasingly focusing on reprogramming TAMs.
The study also discussed the clinical benefit of a treatment used in dogs called MDP, a previously researched immunostimulatory drug that can make these macrophages switch sides again. This approach has worked well in dogs with bone cancer and HSA, making it a hopeful option for future treatments.
Based on their findings, the researchers urge that therapies targeting these immune cells could be promising for treating dogs with Hemangiosarcoma. Additionally, dogs with this cancer could be valuable for testing new treatments to change how these immune cells behave in the tumor environment in human cancer as well.
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