ERBB2 and breast cancer: Clinically approved HER2-targeted therapies such as lapatinib and trastuzumab (Herceptin) have significantly improved the disease-free survival (DFS) of patients with HER2-amplified breast cancers.21, 22 However, eventual resistance to these therapies is observed in the majority of cases, representing a major obstacle to long-term cures.23, 24, 25, 26