June 22, 2017

Study Reveals More Similarities Between Human and Canine Mammary Carcinoma

Researchers have uncovered similarities in the cancer-associated stroma of dogs and humans, providing more evidence to support the field of comparative oncology.
By Laurie Anne Walden, DVM, ELS
A recent study by investigators from the University of Zurich, Switzerland, has uncovered molecular similarities between human and canine mammary carcinomas. The research “further supports the validity of the dog as model for human cancer,” say the authors of the report, which was published in May in the International Journal of Molecular Sciences.
The researchers studied cancer-associated stroma, the microenvironment consisting of extracellular matrix, endothelial cells, fibroblasts, immune cells, and other types of cells surrounding tumors.

Previous studies have shown that with some human cancers of epithelial origin—including mammary carcinomas—the surrounding stroma actually becomes reprogrammed to support cancer growth.
Mammary tumors in dogs are similar to those in humans both clinically and on a molecular level, write the authors. “But whether these tumor cells also influence the surrounding tissue in dogs the same way they do in humans was unknown until now,” said corresponding author Enni Markkanen, Dr med vet, Dr sc nat, of the Institute of Veterinary Pharmacology and Toxicology, University of Zurich, in a press release.
The research team conducted the study to investigate whether cancer-associated stroma in dogs plays a role in tumor growth (as it does in humans), whether it is similar to cancer-associated stroma in humans, and how it is formed. They chose to analyze canine simple mammary carcinomas because these tumors are close correlates in dogs and humans.
The researchers isolated normal stroma and cancer-associated stroma from 13 formalin-fixed, paraffin-embedded samples of canine mammary carcinomas provided by the Institute of Veterinary Pathology of the Vetsuisse Faculty in Zurich. They used immunohistochemistry and reverse transcription quantitative polymerase chain reaction to assess the expression of genes that have been identified as markers of cancer-associated stroma in humans.
The analysis revealed molecular markers of cancer-associated stroma in dogs—the first study to do so, to the knowledge of the authors. The results also suggested similarities (as well as some differences) in the cancer-associated stroma of dogs and humans.
Dogs are valuable models for cancer research because cancer pathophysiology is similar in dogs and humans, say the authors. Mammary tumors in dogs are naturally occurring, as opposed to tumors in genetically modified rodent models of cancer. Studies such as this one improve the understanding of tumor biology and may lead to the development of new treatments for cancer for both species, they write.
“We don’t view our dog patients as test subjects for cancer research,” said Dr. Markkanen in the press release. “But they can help us to better understand breast carcinoma in both dogs and humans and fight it more effectively.”
Dr. Laurie Anne Walden received her doctorate in veterinary medicine from North Carolina State University. After an internship in small animal medicine and surgery at Auburn University, she returned to North Carolina, where she has been in small animal primary care practice for over 20 years. Dr. Walden is also a board-certified editor in the life sciences and owner of Walden Medical Writing, LLC. She works as a full-time freelance medical writer and editor and continues to see patients a few days each month.

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