Wnt-1 is a secreted protein that signals throμgh the Frizzled family of cell surface receptors and is required for normal embryonic development. Wnt-1 activation induces a complex signaling cascade that ultimately leads to the increased expression of over fifty genes. An important component of Wnt-1 signaling is the stabilization, and resulting accumulation, of the intracellular signaling protein, beta-catenine. Wnt signaling induces and maintains the transformed phenotype and, in certain embryonic cell lines, supports self renewal in the absence of significant differentiation. Elevated levels of Wnt proteins are associated with tumorigenesis and are present in numerous human breast cancers. Mature human Wnt-1 is a glycosylated protein containing 343 amino acid residues.