Researchers at the University of Kentucky have provided new insight into why the most severe subtype of breast cancer in humans frequently metastasizes. Tumor cells can exploit a cellular program that promotes cell migration and reduces adhesion between cells to spread to distant sites in the body, causeing metastasis. This cellular program, known as the epithelial-mesenchymal transition, is normally involved in wound healing, tissue remodeling and embryonic development. Increasing cell motility requires a decrease in E-cadherin, which functions to promote cell-cell adhesion. Led by Binhua Zhou, the research team identified a molecule called G9a as a major repressor of E-cadherin expression. Their findings establish that G9a is an important determinant of metastasis in the most severe sub-type of breast cancer, and suggest the development of new therapeutics targeting this pathway could potentially disrupt the metastatic disease.