ERBB2 and neoplasm: Accordingly, trastuzumab is an effective drug to inhibit malignant signaling in ErbB2 overexpressing tumor cells, but it has the disadvantage of (a) interfering with NRG-1/ErbB2 signaling in the heart, which becomes harmful during co-treatment with antracyclines, and (b) allowing an ErbB3-dependent escape route for drug resistance through the upregulation of ErbB3 and formation of ligand-induced ErbB2/ErbB3 oncogenic complexes.