To explore a potential basis for the apparently lack of a role for FAK in mammary tumor development in MMTV-Wnt1 model, we examined mammary gland whole mounts of these mice at an earlier age, as one characteristic feature of this model is Wnt-driven mammary ductal hyperbranching that is accompanied by abnormal alveolar formation in nulliparous mice [4]. Here, WNT1 is linked to breast cancer.