Canine mammary carcinoma is the most common cancer in female dogs and, according to a study published in 2008, accounts for 70% of all female canine cancers.

A new study, published on July 15 in BioMedCentral, explored the microenvironment of canine mammary carcinoma and, specifically, the relationship between cancer cells and macrophages.

The microenvironment of a tumor, the researchers discovered, contains tumor-associated macrophages or TAMS that hold M2, an activated phenotype that causes cancer cells to grow. The cancer cells, too, aid that growth.

The researchers are from the Royal (Dick) School of Veterinary Studies and Roslin Institute at the University of Edinburgh in the UK, and the Department of Veterinary Science at the Universidade de Trás-os-Montes e Alto Douro in Portugal.

Study results showed that canine mammary carcinoma cells influence the macrophage phenotype. The cancer cells cause a change in the phenotype and induce proliferation in the macrophage, which then causes the macrophage to stimulate cancer cell proliferation.

With the complexity of the tumor microenvironment and the dual roles of the cytokine CSF-1 and CCL-2 found for macrophage activation, the researchers believe future analysis of the macrophages’ different states of activation will offer insights about the complexity of their activation.