"DNA Repair Deficiency as a Susceptibility Marker for Spontaneous Lymphoma in Golden Retriever Dogs"

As a breed, Golden Retrievers have a high incidence of lymphoproliferative diseases, particularly lymphoma. Evidence in prior studies has suggested that deficiencies in heritable factors regarding DNA repair capabilities may be linked to the development of lymphoma. It has also been previously proposed that sensitivity to the induction of chromosome damage is an indirect measure of individual DNA deficiency and, thus, may be an indicator for predisposition of lymphoma. Therefore, this study involved exposing golden retrievers to various doses of ionizing radiation or a chemical mutagen, bleomycin, and then evaluating their DNA repair abilities at different times.Twenty-one golden retrievers with lymphoma, twenty healthy golden retrievers, and twenty mix breed canines were included in the study. One hypothesis was that the lymphocytes in golden retrievers with lymphoma would have enhanced sensitivity to the induction of chromosome damage over healthy golden retrievers, which validates the implications mentioned above from other studies. The researchers also hypothesized that lymphocytes in both healthy and non-healthy golden retrievers would overall have enhanced sensitivity over the mix breed dogs, which would indicate that as a breed, golden retrievers have a DNA repair deficiency and would contribute to explaining why this breed has a high risk for lymphoma.

The 75th percentile of the normal mix breed population for chromatid breaks after exposure was used to classify sensitivity (greater than the 75th percentile indicated sensitivity).The results demonstrate that, in almost all conditions, golden retrievers with lymphoma had a significantly higher frequency of chromatid breaks or were significantly more chromosomal sensitive than health golden retrievers. Additionally, between healthy golden retrievers and mixed breed dogs, there was no significant difference in percent of sensitivity. Therefore, it was concluded that sensitivity does imply a predisposition for lymphoma in golden retrievers. Furthermore, this study proved that this susceptibility is individual-specific, or that golden retrievers are not susceptible as a breed, and so they cannot be considered DNA repair deficient as a breed.

Thamm, D., Grunerud, K., Rose, B., Vail, D., and Bailey, S. 2013 DNA Repair Deficiency as a Susceptibility Marker for Spontaneous Lymphoma in Golden Retriever Dogs: A Case-Control Study. PLoS ONE 8(7): e69192