Trastuzumab (Herceptin) binds to the HER2 protein, which is upregulated on certain breast cancer cells, but can also bind to HER2 expressed on cardiomyocytes, interfering with the normal NRG-1/ErbB2 signalling axis resulting in cardiomyocyte apoptosis (106). The gene discussed is ERBB2; the disease is breast carcinoma.