Mammary neoplasm affects a population of intact and elderly female dogs and 50% are malignant. In order to study this disease, cell culture is as a promising preclinical model, creating the opportunity to deposit cell lines at a cell bank, allowing a great reproducibility of the assays and making the validation of the results more reliable. Another important aspect is the possibility to establish models for better understanding tumour characteristics, such as vasculogenic mimicry. Due the importance of cancer cell lines in preclinical models, this study aimed to establish and characterize primary cell lines from canine mammary gland tumours according to immunophenotype and tumorigenicity, and with its ability to form vasculogenic mimicry-like structures in vitro and in vivo. Cell cultures were evaluated for morphology, phenotype, vasculogenic mimicry and tumorigenicity abilities. We collected 17 primary mammary carcinoma and 3 metastasis and had a satisfactory result in 10 of them. All cell lines presented spindle shape or polygonal morphology and expressed concomitant pan-cytokeratin and cytokeratin 8/18. Four cell lines had vasculogenic mimicry ability in vitro and two of them showed in vivo tumorigenic potential and forming VM in the xenotransplant tumour. Cell characterization of those lines will help to create a database for more knowledge of mammary carcinomas in dogs, including studies of tumour behaviour and new therapeutic targets.

Canine mammary tumors (CMT) are the most common cancer in noncastrated female dogs. Interestingly, triple-negative tumors are the most common molecular subtype in female dogs. In this study, we proposed to evaluate the expression of VEGFR-2, PDGFR and microvascular density (MVD) in a group of metastatic and nonmetastatic triple-negative CMT and compare the expression based on clinical parameters. Twenty-six female dogs with triple-negative mammary tumors were divided into three groups: nonmetastatic tumors (NMT) (N=11), tumors with lymph node metastasis (LNM) (N=10) and tumors with lung metastasis (LM) (N=5). We observed increased VEGFR-2 expression in LNM compared with NMT and a positive correlation between tumor grade and VEGFR-2 expression. A positive correlation was noted between VEGFR-2 and PDGFR expression. Regarding microvascular density (MVD), we identified a higher number of vessels in primary tumors with lymph node metastasis and lung metastasis compared with tumors with no metastasis. The primary tumors with lung metastasis exhibited an increased MVD compared with carcinoma with lymph node metastasis. Overall, our results suggest a deregulation of VEGFR-2 and PDGFR and high MVD in metastatic tumors, indicating a role for angiogenesis in tumor progression.