Objective To establish an in vitro model of canine mammary epithelial cells for the study of the carcinogenesis and development of breast cancer.

Method The cells were separated from canine milk and cultured. The cell growth curve was described using the CCK-8 assay. The expression of cytokeratin 8 was determined using cell immunofluorescence to identify mammary epithelial cell.

Result and conclusion After cultured for 3 days, the cells were cloned with a shape like a typical island, and there were also a few phagocytes. Cultured for a few more days, the cells began to coalesce and form monolayers which could secrete lactogenesis drops. The phagocytes vanished after several passages. The cell growth curve was similar to a "S" shape. The immunofluorescent staining results showed that the cell of cytokeratin 8 was positive. The results indicated that the canine mammary epithelial cells separated from canine milk were highly pure and rapidly growing. This study established a model to isolate and culture massive canine mammary epithelial cells in a short time.