Wnt signaling and mammary tumorigenesis

Wnt expression patterns during mammary development support a role for Wnts in breast development and in mammary epithelial responses to systemic hormo nes. The deregulation of Wnt signaling also plays a role in breast cancer. Activation of the Wnt signaling pathway is a major feature of several human neoplasias and appears to lead to the cytosolic stabilization of a transcr iptional co-factor, beta -catenin. This co-activator can then regulate tran scription from a number of target genes including the cellular oncogenes cy clin D1 and c-myc. This review will summarize the current state of knowledg e of Wnt signal transduction in a range of model systems and will then addr ess the role of Wnts and Wnt signaling in mammary development and cancer.