Exploring Risk Factors for Canine Lymphoma
Lymphoma, or cancer of the lymphoid cells of the immune system, is a common cancer in dogs. Molecular studies have identified at least 30 different sub-types of canine lymphoma based on T-cell or B-cell involvement, genetic mutations, and more. Genetic mutations and exposure to environmental toxins are some of the many suspected causes of canine lymphoma. However, very little is known about why these mutations accumulate in certain dogs. This knowledge is critical to develop prevention strategies – preventing the build-up of harmful mutations and therefore avoiding development of canine lymphoma.
The AKC Canine Health Foundation (CHF) and its donors have invested more than $2.6 million in research to improve our understanding of lymphoma. With funding from CHF Grant 02318: Genetic and Environmental Risk for Lymphoma in Boxer Dogs, investigators at the University of Wisconsin, Madison set out to learn more about the combinations of genetic mutations and toxin exposures that contribute to canine lymphoma. In humans, inherited mutations that affect enzymes responsible for breaking down toxic chemicals in the body are known to increase the risk of developing Non-Hodgkin’s lymphoma. Could the same be true in dogs?
Glutathione-S-transferases (GSTs) are enzymes that process and break down toxic chemicals that could otherwise damage DNA. If genetic mutations are present that decrease the activity of these enzymes, more toxic chemicals remain in the body, and more DNA damage occurs. Investigators hypothesized that the high risk of lymphoma in Boxers is related to the presence of more GST enzymes with low activity, more DNA damage, and more exposure to environmental chemicals. They compared the frequency of four specific GST enzyme variations in a population of Boxers with that found in dogs of similar age from other breeds. They also examined the amount of DNA damage in a group of Boxers with lymphoma compared to unaffected, geriatric Boxers.
Results recently published in the Journal of Veterinary Internal Medicine1 showed that the number of low-activity GST enzymes present in Boxers was not statistically different than that found in other breeds. Nor was there more DNA damage present in the white blood cells of Boxers with lymphoma compared to unaffected Boxers. These findings suggest that the higher risk of lymphoma in Boxers is not related to a breed-specific accumulation of DNA damage.
Results did show that Boxers living within 10 miles of a nuclear power plant were five times more likely to develop lymphoma. Boxers living within 2 miles of a crematorium or chemical manufacturer or supplier were also more likely to develop lymphoma. This evidence supports the premise that exposure to environmental chemicals and industrial waste does contribute to lymphoma risk in dogs.
Additional study is needed to learn more about the interactions between genotype and environmental exposures in dogs with lymphoma. CHF-funded investigators at North Carolina State University, Michigan State University, and the University of Washington are actively exploring the amount and characteristics of genetic mutation accumulations in various types of canine lymphoma. As part of CHF’s commitment to One Health, additional study into environmental exposures and the development of cancer is also underway. Results could help prevent cancer in dogs and humans. Learn more about this important research at www.akcchf.org/lymphomaRPA.
- Craun, K., Ekena, J., Sacco, J., Jiang, T., Motsinger‐Reif, A., & Trepanier, L. A. (2020). Genetic and environmental risk for lymphoma in boxer dogs. Journal of Veterinary Internal Medicine.
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