Using the murine mammary tumor virus (MMTV)-Wnt-1 transgenic model of mammary carcinoma, Schroeder and his colleagues have identified an unvarying association between β-catenin and epidermal growth factor receptor/c-Neu (ErbB1/ErbB2) heterodimers in mammary gland tumors, indicating a requirement for ErbB signaling in Wnt-mediated tumorigenesis [46]. Here, WNT1 is linked to breast carcinoma.