In the last several years, our laboratory has focused on studying the biologic features of erbB3 receptor in erbB2+ breast cancer, and published a serious of articles indicating that activation of erbB3 signaling, mainly through PI-3K/Akt pathway, is essential for erbB2-induced therapeutic resistance to tamoxifen [24], paclitaxel [25], and trastuzumab [26]. This evidence concerns the gene ERBB2 and breast cancer.