A less invasive method for orthotopic injection of breast cancer cells into the mouse mammary gland.

Breast cancer is the most common type of cancer diagnosed in women, and the second most common cause of cancer-related deaths in women in North America. The use of laboratory mice in research is an essential tool for the study of breast cancer biology and for pre-clinical therapeutic development. While subcutaneous flank injections of cancer cells are widely used for studying breast cancer biology and for exploring novel therapies, orthotopic xenografting of tumors into the mouse mammary gland allow for the study of breast cancers in a biologically relevant microenvironment. In this study we report a modification of the method of orthotopic injections of cancer cells into the mouse mammary gland which greatly reduces the effects of surgery in mice including decreased wound size, procedure time and anesthesia. It also removes the risk of accidentally puncturing the peritoneal cavity. Consequently post-operative animal handling and stress are significantly reduced. All of these advantages are present without compromising procedure success rate. Therefore, this modification makes orthotopic mammary gland injection a more efficient procedure and greatly improves animal welfare.