We previously reported that the three RTKs, erbB2, erbB3, and IGF-1R interacted with each other to form a heterotrimeric complex, which activates the downstream signaling, such as PI-3 K/Akt or MEK/MAPK pathways and Src kinase in trastuzumab-resistant breast cancer cells [28]. Here, ERBB2 is linked to breast cancer.