Researchers already use canine mammary tumors to help study breast cancer in humans. But a new study aimed to determine how comparable the tumors are in a specific type of cancer.

The study was concerned with cancer-associated stroma (CAS). It aimed to characterize the expression of CAS in both people and dogs and then to determine whether the underlying biology of CAS was the same in both. The open-access study was published in the May 2017 issue of the International Journal of Molecular Sciences.

While carcinomas in dogs have been used to as models for human breast carcinomas, CAS has not been studied as closely, and it has not been determined whether CAS is expressed the same way in dogs and humans. The aim of this study was to determine how comparable CAS in dogs and people is.

Researchers isolated CAS and normal stroma from 13 canine carcinomas and analyzed the expression of 7 known human CAS markers. To isolate RNA, researchers use a laser-capture microdissection. Normal stroma and CAS were isolated from the same tissue section to ensure the tissue quality of both samples was similar.

One encouraging finding showed that mRNA levels of ACTA2, COL1A1, and FAP were all significantly increased in the carcinomas when compared to the normal stroma, a finding consistent with studies on human samples. This data suggests the underlying biology of CAS is highly comparable and that COL1A1, ACTA2, and FAP can be used as markers of CAS in canine mammary carcinomas.

However, some other markers for human CAS, such as the protein PDGFRβ, were not significantly different in the canine tumor and normal stroma samples. The researchers hypothesized this could be due to their small sample size. A few other markers that they had difficulty detecting could also be attributed to the quality of the samples or where the samples were taken from.

Ultimately, the study was not able to definitively determine whether the underlying biology of CAS in dogs and people is perfectly comparable. While there were strong similarities between CAS in dog and human samples, the differences suggest that future studies need to be done with larger datasets.

Because the study is one of the first to compare CAS biology in dogs and humans, more studies can build off the initial analysis. While the comparability is still indeterminate, the study did conclude that their results support the validity of using dogs as a model for human cancer.

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