In our case, although MM-121 itself cannot trigger ADCC, because of its IgG2 isotype [41], it is possible that inactivation of erbB3 with MM-121 may increase trastuzumab’s binding efficiency to the tumor xenografts-established from BT474-HR20 cells, and subsequently enhance trastuzumab-mediated ADCC. This evidence concerns the gene ERBB3 and neoplasm.