We are investigating new molecular mechanisms of tumor suppression to design new diagnostic and therapeutic strategies in breast cancer. We combine investigations in signaling pathways and in transcriptional regulation with directed clinical studies. We focus on the Wnt pathway, which has emerged as a major pathway in breast and other cancers, and HBP1, as a transcriptional repressor that is also a suppressor of Wnt signaling. HBP1 mutations are clinically associated with invasive breast cancer. Thus, HBP1 is a new tumor suppressor gene with clinical and molecular impact on invasive breast cancer.