Metalloproteinases (MMPs) are a family of proteins that are involved in the breakdown of the extracellular matrix during normal cellular events, including reproduction, tissue remodeling and embryonic development. MMPs are crucial in tumor invasion and building of metastatic formations because of their ability to degrade extracellular matrix proteins such as fibronectin, laminin, gelatins and/or collagen. MMP-27 (matrix metallopeptidase 27) is a 513 amino acid secreted protein that is expressed in B-cells. Belonging to the peptidase M10A family, MMP-27 contains four hemopexin-like domains, which is suggested to be involved in substrate recognition. MMP-27, along with other MMP family members, is associated with breast cancer development and tumor progression.