Canine Mammary Cancer Stem Cells are Radio- and Chemo- Resistant and Exhibit an Epithelial-Mesenchymal Transition Phenotype

Abstract

Canine mammary carcinoma is the most common cancer among female dogs and is often fatal due to the development of distant metastases. In humans, solid tumors are made up of heterogeneous cell populations, which perform different roles in the tumor economy. A small subset of tumor cells can hold or acquire stem cell characteristics, enabling them to drive tumor growth, recurrence and metastasis. In veterinary medicine, the molecular drivers of canine mammary carcinoma are as yet undefined. Here we report that putative cancer stem cells (CSCs) can be isolated form a canine mammary carcinoma cell line, REM134. We show that these cells have an increased ability to form tumorspheres, a characteristic of stem cells, and that they express embryonic stem cell markers associated with pluripotency. Moreover, canine CSCs are relatively resistant to the cytotoxic effects of common chemotherapeutic drugs and ionizing radiation, indicating that failure of clinical therapy to eradicate canine mammary cancer may be due to the survival of CSCs. The epithelial to mesenchymal transition (EMT) has been associated with cancer invasion, metastasis, and the acquisition of stem cell characteristics. Our results show that canine CSCs predominantly express mesenchymal markers and are more invasive than parental cells, indicating that these cells have a mesenchymal phenotype. Furthermore, we show that canine mammary cancer cells can be induced to undergo EMT by TGFβ and that these cells have an increased ability to form tumorspheres. Our findings indicate that EMT induction can enrich for cells with CSC properties, and provide further insight into canine CSC biology.

Mammary Stem Cell Research in Veterinary Science: An Update

“…Hereby, it was found that the CSC were more resistant to the actions of interferon-omega than the REM134 and CAT-MT cell lines [75]. A similar result was found with the chemotherapeutic drug doxorubicin, where spheres derived from the canine adenocarcinoma cell line CHMp and REM134 had chemoresistant characteristics [72,73]. Taken together, it can be stated that such sphere assays are suitable models to test therapeutic strategies aimed at eradicating CSC.…”

“…Moreover, these CD44 + CD24 -populations showed a high ALDH activity and were capable of initiating tumors in NOD/SCD mice [72]. CSC spheres, isolated from REM134, were shown to express the embryonic stem cell markers Oct4 and Nanog as assessed by nonquantitative RT-PCR analysis [73]. The group of Ferletta et al [74] isolated spheres from the mammary tumor cell line CMT-U229 (an atypical benign mixed mammary tumor), characterized these spheres by IHC and found a similar expression pattern to what had been described by other research groups [72,73].…”

Possible Role of Snail Expression as a Prognostic Factor in Canine Mammary Neoplasia

“…Recent studies have described plasticity of epithelial cells that undergo the epithelialemesenchymal transition (EMT) that is necessary for the invasion and metastasis of carcinomas (Vincent-Salomon and Thiery, 2003;Huber et al, 2005;Pereira et al, 2010). EMT was originally defined in gastrulation and neural crest delamination during embryonic morphogenetic remodelling (Reiman et al, 2010).…”

Salinomycin inhibits canine mammary carcinoma in vitro by targeting cancer stem cells

“…Previous studies have used this method to analyze the sphere-forming ability of canine mammary CSCs (15,23). This method has also been used to investigate novel therapeutic drugs in humans and canines (14,24).…”

“…In canines, mammary CSCs are associated with a higher grade of carcinoma and poor prognosis (7,8). In addition, canine mammary CSCs are typically resistant to common cancer therapies (9,15). Therefore, it is important to identify novel drugs targeting CSCs for the eradication of canine, and human, mammary tumors.…”