Establishment and characterization of a new triple-negative canine mammary cancer cell line

Canine mammary tumor (CMT) has always been an ideal animal model for human breast cancer (HBC) research, however, there is a lack of various established CMT cell lines corresponding to HBC cell lines. This study was designed to establish a new type of CMT cell line. The primary tumor, CMT-7364, was identified as the intraductal papillary carcinoma, and showed negative immunoreactivity to estrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor receptor-2 (HER-2) by immunohistochemistry (IHC) analysis. The CMT-7364 cell line from this primary tumor also shows a negative immunoreactivity to ER, PR, and HER-2, and was negative to epithelial cell markers and positive to mesenchymal cell markers by immunocytochemistry (ICC) analysis. This cell line, which has been stably cultured for more than 115 passages, and was characterized by epithelial origin with the expression of the epithelial antigen by ICC analysis and invasion ability by transwell analysis. In vivo, tumor mass and metastases in the lung were found after inoculating the CMT-7364 cells in the nude mice model, and the immune-complete mice model respectively. The tissues from the xenograft tumor were also negative to ER, PR, and HER-2 by IHC analysis. Thus, a novel triple negative canine mammary cancer cell line, CMT-7364, was successfully established, which could be used as a promising model for the research of immunotherapy and Epithelial-Mesenchymal Transition (EMT) mechanism of the triple-negative breast cancer both in canine and human.